生物科技快报Bulletin of Biological Science & Technology

中国科学院成都生物研究所情报中心

目 录[科技动态] 2006 年度《科学》杂志评选出的十大科技进展….……….……............................…….1关于热带雨林动态和稳定性的中性理论…..……………………………..……..…….….3

原始森林是重要的碳汇？….……..…..………………………………..…..……………...5

与肥胖有关的肠道微生物……….………………...……………......…………………..…5

Cytohesins 与胰岛素抗性之间的关系….……………….…..…..…………………...……7

关于衰老过程的两个理论可能是一致的…………...…..……………..……...……....…10

模型揭示人类流感的进化………....…………..............………………………….…..….11

一个新的细胞周期调控因子…………………..…...……………………………….…....12

GpMST1 被克隆和定性..………...……………..………..…………………..…………......15

纳米颗粒控制微流体.…...……………………………………………………...………...18

在实验室中观察细菌的进化…………………………………………………...………...18

胰岛素增敏新线索……...………………………………………………………...........…19

压制艾滋病病毒…………….…….……………..….….………………………………....20

老药发现新目标……..…………...…………………………………………....……….....20

科学家发现分子差异能去除水稻中的杂草………...…...……….…....…………….…..21

负碳的生物燃料………………………………………….……..........................….……..22

[技术方法]

新型 siRNAs 能够区分基因变异体………………………..…………………….…..…...22

[技术消息] 生物柴油生产现状及技术进展…………….…………….................................................24

美国拟创建生物能源中心…………….……………………………………….……....…34

生物燃料热背后的事实 (附有相关英文文章)……..….……………..….………......….35

《科学》发表的有中国大陆科学家署名的文章……………………….….…...……….57

2006 年 12 月 20 日第 11 期 （总第 152 期）

2006 年度《科学》杂志评选出的十大科技进展

研究人员在 2006 年完成了数学史的一个主要章节，对百年难题庞加莱猜

想达成共识，这个有关三维空间抽象形状的问题终于被解决了。《科学》和其出

版者、非营利的美国科学促进会将这一成果评选为今年的第一大进展。

庞加莱猜想属于被称为拓扑的数学分支，通常被描述成“橡皮上的几何”，因

为它涉及能够经历任意拉伸的表面。这个 1904 年由庞加莱提出的猜想描述一

个空间是否与“超球面”(四维球体的三维表面)等价的检验。

基本上与外界隔绝地工作了 7 年的俄罗斯数学家 Grigori Perelman 2002

年在互联网上提交了三篇文章的第一篇，这些文章把庞加莱猜想作为一个更雄

心勃勃的结果的一部分，给其证明提供了一个轮廓。但是在 2003 年访问美国

之后，这位俄罗斯数学隐士回国后停止了与外界的电话和电子信往来。到了

2006 年，其他人终于赶了上来。三个独立的小组写出报告填补了佩雷尔曼的1

证明中缺失的关键细节，现在佩雷尔曼的同行几乎都没有疑问地认为他证明了

这个著名的难题。

《科学》评选出的其它 9 项进展如下，排名不分先后：

从化石中取出 DNA: 研究人员用一种解码和分析DNA 的新技术，从尼安

德特人和猛犸化石中捕获到遗传信息。

冰架在缩小: 研究人员今年记录了这一令人不安的趋势。南极洲和格陵兰岛的

冰架都在以更快的速度消失到海洋中。

鱼迈出的第一步: 一个具有结实的连接着的鳍的鱼化石的发现曾是 2006 年的

头版新闻。这种鱼是有肢脊椎动物已知的最近亲，它为生命如何离开海洋登上

陆地提供了一个视窗。

隐身术的科学: 虽然它看上去一点也不像哈里波特的魔术披风，科学家今年制

造的隐身“斗篷”是第一个将物体在视觉上屏蔽起来的初步装置。这个装置引

导入射的微波使其既不反射、也没有影子。 2

黄斑病变患者的希望: 研究一种被称为老年黄斑病变失明的研究人员揭示，药

物 ranibimuzab 能改善某些患者的视觉，他们还找到了几个影响人们该症易

患性的基因。

生物多样性是如何发生的: 从沙滩小鼠、到果蝇、到蝴蝶，这些不同的动物帮助

科学家发现导致新物种进化的遗传变化。

显微学的新前沿: 今年，生物学家用新的显微技术来帮助他们观察小于 200 纳

米的细节，为了解细胞和蛋白质的精细结构提供了更清晰的视野。

制造记忆: 2006 年的几个发现使神经科学家对了解大脑如何记录新记忆更接

近了一步。增强神经元之间连接的被称为“长时程增强”的过程看来很可能是

记忆的基础。

新一类的小 RNA: 科学家发现了一类关闭基因表达的新小RNA 分子，把它们

命名为 "Piwi-干扰 RNA"。

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本年度的崩溃-科学骗局: 干细胞研究者黄禹锡以及其合作者曾在《科学》发表

两篇重要论文，他们制造的骗局在 2006 年被彻底调查了，本年度也发生了几

起其它的科学不端行为。

值得注意的领域: 《科学》预测来年的热门领域和主题包括整基因组相关性研究

光晶格、寻找宇宙的原始氢、以及比较灵长类的基因组。

社论：Breakthrough of the Year, Donald Kennedy

新闻：Breakthrough of the Year: The Poincaré Conjencture--Proved,

Dana Mackenzie

新闻：Breakthrough of the Year: The Runners-Up, The News Staff

2006 年 12月 22日 美国《科学》周刊 314卷 第 5807 期

关于热带雨林动态和稳定性的中性理论

生态学中性理论、包括 Stephen Hubbell 的关于生物多样性和生物地理

的统一中性理论，旨在通过假设类似物种之间的差别是中性的或与其成功无关4

的来解释生态群落中物种的多样性和相对丰度。尽管所涉及的物种相互作用网

络很复杂，近乎静止状态的生态系统总体行为可以表现出令人吃惊的简单性。

然而，这样的研究工作中几乎没有一个是研究热带雨林的动态和稳定性的 。

Azaele 等人正好填补了这个空白，他们建立了一个关于生态系统动态演化的

分析理论。该理论与巴拿马 Barro Colorado 岛上的热带森林中的物种更替

分布非常一致。该新模型为将诸如非中性动态以及依赖时间和地点的变化包括

进中性模型的基本框架中提供了一个出发点。

Nature 444, 926-928 (14 December 2006)

FIGURE 1. Relative species abundance plot in the BCI forest from

the 1990 census (Center for Tropical Forest Science website).

The individuals of more than 10 cm d.b.h. in this tropical forest are binned with the method of refs 7, 29. The inset shows the same histogram for the individuals of more than

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1 cm d.b.h. for the same forest and yields consistent estimates of the model parameters and temporal scales within the error bars. The estimated parameters are robust within error bars on changing the nature of binning of the empirical data to non-overlapping bins. The points are the best fits to the mean number of species with population between 2n - 1 and 2n, as given by equation (1). The fit for large x is readily improved at the cost of introducing an additional parameter (see Supplementary Information for error analysis and other details). Note that the RSA plot for individuals of more than 10 cm d.b.h. is smoother at low abundance than the plot for individuals of more than 1 cm d.b.h. This is to be expected because younger populations are subject to larger fluctuations than older ones.

FIGURE 2. STD for the interval 1990–95 in the BCI forest.

The main panel shows results for individuals of more than 10 cm d.b.h., and the inset results for individuals of more than 1 cm d.b.h. (Center for Tropical Forest Science website). We have defined the new variable r = log(), which is distributed as g(r) = erPSTD(er,t), where PSTD( ,t) is given by equation (2). Data are plotted

with a linear binning in the r = log( ) axis and fitted to g(r). b/D is obtained from fitting the RSA data in 1990 (see Fig. 1). The best-fit parameter is found to be 4,400 years for individuals of more than 10 cm d.b.h., and 3,900 years for individuals of more than 1 cm d.b.h. The fits of both RSA (see Fig. 1) and STD for individuals of more than 10 cm d.b.h. are systematically better than those for individuals of more than 1 cm d.b.h.

FIGURE 3. Restricted relative species abundance.

Plot of the mean number of species originally present in an ecosystem with population between 2n - 1 and 2n after time t has evolved, as given by equation (3). The circles denote the steady state at

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t = 0, namely the standard RSA; the triangles correspond to t = 100 years; the diamonds to t = 1,000 years; and the stars to t = 10,000 years. The parameters are those deduced from the RSA of the BCI plot in 1990 for more than 10 cm d.b.h. (see Supplementary Table 1). Note the shift of the maximum of the curve to the right and that rare species are more prone to extinction.

原始森林是重要的碳汇？

一项新研究提出，中国南方的一个原始森林从大气中吸收二氧化碳的量比

对估计的要多。传统上认为，原始森林作为碳汇的意义不大，因为原始森林所

吸收的碳称认为与森林中其它生物体降解有机物所释放的碳基本平衡，这个过

程被称为"呼吸"。周国逸和同事测量了中国广东省的鼎湖山森林自然保护区原

始森林土壤层中有机碳的水平。他们报告说，从 1979到 2003 年中土壤积累

的大气碳的速度比期待值高，造成这个增加的原因现在还不清楚，作者说他们

的发现指出了进一步研究原始森林对全球环境变化的复杂响应的必要性。

简报：Old-Growth Forests Can Accumulate Carbon in Soils, Guoyi

Zhou, et al. 2006 年 12月 1日 美国《科学》周刊 314卷 第 5804 期

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与肥胖有关的肠道微生物

肠道微生物可以帮助我们完成我们本身不能完成的一些代谢任务。从某种

意义上来说，它们的基因是智人（Homo sapiens）“多源基因组”

（metagenome）的一部分。本期两篇相关的论文帮助说明了这一点，它们

为微生物在肥胖的形成中所起的作用提供了证据。对肥胖者肠道中两组占主导

地位的细菌的含量多少所做的一项研究工作表明，Bacteroidetes细菌数

量的增加与体重降低相关联。对遗传性肥胖的小鼠所做的一项研究显示，与同

窝出生的瘦的小鼠相比，它们肠道微生物群落利用能量的能力要强一些，而将

该微生物群落移植进肠道中没有细菌的小鼠体内时，这种性状也能被转移过去。

这项工作说明，与肥胖相关的肠道微生物也许是一种生物标记，并且可能是一

个治疗目标。

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Nature 444, 1022-1023 (21 December 2006)

FIGURE 1. Correlation between body-weight loss and gut microbial

ecology.

a, Clustering of 16S ribosomal RNA gene sequence libraries of faecal microbiota for each person (in different colours) and time point in diet therapy (T0, baseline; T1, 12 weeks; T2, 26 weeks; T3, 52 weeks) in the two diet-treatment groups (fat restricted, FAT-R; carbohydrate restricted, CARB-R), based on UniFrac analysis of the 18,348-sequence phylogenetic tree. b, Relative abundance of Bacteroidetes and Firmicutes. For each time point, values from all available samples were averaged (n was 11 or 12 per time point). Lean-subject controls include four stool samples from two people taken 1 year apart, plus three other stool samples6. Mean values s.e. are plotted. c, Change in relative abundance of Bacteroidetes in subjects with weight loss above a threshold of 2% weight loss for the CARB-R diet and 6% for the FAT-R diet.

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Cytohesins 与胰岛素抗性之间的关系 胰岛素抗性综合症是各种不同器官不能对胰岛素做出足够反应的一种症状，是二型糖尿病发病的一个主要危险因素。对绝大多数受影响的人来说，造成该症状的分子缺陷尚不清楚。现在，Hafner 等人发现，Cytohesins（一类调控蛋白，以前被发现参与与胰岛素相关的代谢）的化学抑制能导致小鼠肝脏对胰岛素产生抵抗力。这表明，受损的 Cytohesin功能是胰岛素抗性的一个可能的原因，Cytohesin 的激发成分可用来治疗这种疾病。在另一项研究中，研究人员发现，果蝇体内与 Cytohesin 相当的 Steppke 是胰岛素信号作用的一个重要构成部分。这两篇论文一起为 Cytohesins 在胰岛素通道中所起的中心作用提供了独立证据，并且表明，通过 Cytohesin 对该通道的控制至少已有 8亿年时间了。

Nature 444, 941-944 (14 December 2006)

FIGURE 1. Structure and characterization of SecinH3.

a, Molecular structures of SecinH3 (left) and the negative control compound D5 (right). For details on the synthesis and characterization of each compound, see Supplementary Methods

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and Supplementary Fig. 2. b, SecinH3 does not affect Golgi structure. Compared to untreated cells, no significant disturbance of Golgi integrity is observed at SecinH3 concentrations of 10 M and 50  M, respectively, whereas BFA leads to complete Golgi destruction at 20  M. Golgi membranes were visualized using an anti-giantin antibody.

FIGURE 2. SecinH3 inhibits insulin signalling in HepG2 cells.

a, Effect of SecinH3 on insulin-dependent IGFBP1 expression, determined by quantitative PCR (qPCR) (n = 3). b, Insulin-induced ARF activation is inhibited by SecinH3 (n = 4). Lower panel: representative western blot of activated ARF6. c, Cells were transfected with the indicated siRNA or non-silencing control siRNA (ns) and IGFBP1 expression was determined by qPCR (n = 3). d, SecinH3 reduces Akt phosphorylation. pAkt was detected by immunoblot (see Supplementary Fig. 8), using actin for normalization (n > 6). e, Effect of SecinH3 on insulin receptor and

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IRS1 complex formation. IR (left) and IRS1 (right) were immunoprecipitated, and coprecipitated proteins were detected by immunoblotting. Error bars: s.d.

FIGURE 3. Impaired

cytohesin function results

in hepatic insulin

resistance.

a, Gene expression in liver was determined by qPCR in mice fed with (black) or without SecinH3 (grey). Upper part: change in gene expression as compared to starved animals (set as 1). Lower part: ratio of gene expression in SecinH3-fed versus control animals (n = 6). Insulin-repressed genes are overexpressed (green); insulin-induced genes are underexpressed (red). b, Glycogen levels31 in livers of SecinH3-fed and control mice, expressed as g glucose units per mg liver (n = 5). Serum levels of insulin (c), glucose (d), triglycerides (e), non-esterified fatty acids (NEFA) (f) and 3-hydroxybutyrate (3-HB) (g) were determined in non-starved SecinH3-fed and control mice (n = 8). *P < 0.05, **P < 0.01, ***P < 0.001. Error bars: s.d.

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关于衰老过程的两个理论可能是一致的 此前，人类 XPF 基因的突变一直被与温和型的早衰（progeria）联系在一

起。现在，研究人员在一个 15岁的男孩身上识别出了一个以前不知道的、引起

严重早衰的 XPF突变（XFE）。XPF 的这一突变体形式的性质表明，两个关于

衰老过程的看似根本不相同的理论可能是一致的。 有些人认为，衰老是由基因

调控的；另一些人认为，衰老是由于 DNA损伤的逐渐积累。这两种观点可能

都是正确的。被研究人员用遗传工程方法来模拟这种症状的年轻小鼠，表现出

正常年老小鼠的很多特征。这些特征包括诱导产生的胰岛素信号作用、细胞死

亡增加、以及高抗氧化剂水平和高DNA修复活性。这些发现与 DNA损伤来自

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与衰老相关的功能下降的一个模型是一致的，但遗传学规律（尤其是对胰岛素

信号通道而言）影响损伤积累的速度有多快以及功能损失的速度有多快。该发

现的一个意义是，通过增强DNA修复体系，也许有可能延长寿命或改善老年

时的身体适应性。

Nature 444, 1038-1043 (21 December 2006)

FIGURE 1. Molecular characterization of progeroid patient 'XFE'.

a, Clonogenic survival assay measuring UV-radiation sensitivity of wild-type (WT), XFE and xeroderma pigmentosum patient primary fibroblasts (XP-F, XP-C and XP-A). b, RNA synthesis recovery after UV irradiation of patient fibroblasts. c, Immunodetection of XPF in nuclear extracts of patient fibroblasts (normal C5RO, mild xeroderma pigmentosum patient XP42RO and patient XFE). Cross-reacting bands demonstrate equal protein loading. d,

Immunodetection of ERCC1 in the same samples. e, Clonogenic survival assay measuring sensitivity of patient fibroblasts to the crosslinking agent mitomycin C. Error bars (a, b, e) indicate s.e.m. of three experiments.

FIGURE 2. Progeroid characteristics of Ercc1-/- mice.

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a, Ercc1-/- mouse and wild-type littermate at 3 weeks of age. b, Lifespan of Ercc1-/- mice (n = 27). c, Footprint analysis of 3-week-old mice. Forepaws were painted purple, hind paws green. The arrows indicate gait trajectory. Fore- and hind-prints are not superimposed in mutant animals, a diagnostic criteria of ataxia. d, Radiographs demonstrating kyphosis in an aged wild-type and in an Ercc1-/- mouse, but not in a young wild-type mouse. e, Clonogenic survival assay measuring the sensitivity of primary mouse embryonic fibroblasts to the crosslinking agent mitomycin C. Error bars indicate s.e.m. for three experiments, each averaging three replica platings of cells.

模型揭示人类流感的进化

一个人类季节性流感的模型展示了几十年间流感变异的动力学，它显示，

虽然流感病毒在不停地突变，只是每 2到 8 年才具有新的强度。搞清楚流感的

变化至关重要，因为它在世界范围具有高度的发病率和致命率。Katia Koelle

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和文章合作者建立了一个展示流感随时间发展的进化史的模型。这个模型显示，

大多数流感病毒的突变是中性的。偶然地一个小突变引起蛋白的大变化，使其

不被可能的受害者的免疫系统所识别。这个病毒在短时间内利用能不被识别地

传播导致流感的大爆发甚至带来死亡。病毒毒性的增加是由 hemagluttinin 分

子的一个主要变化引起的。病毒在下几个流感季节的连续突变也许会导致小的

结构变化，但是受害者会有某种程度的交叉免疫力，能够控制病毒的复制。病

毒毒性从而减弱，形成新的密切相关的毒株簇。几年后，当一个突变的“逃

逸”引起又一次流感高峰时这个循环再次开始。该模型揭示了季节性流感的两

个主要的突现模式: 一个遗传多样性的爆发-减弱模式，和一个在簇转变后的复

发期。除了与流感发作成功地匹配外，这个模型帮助机械地结合了病原体流行

病学与进化。模型也许也适用于其他突变影响疾病发展的疾病，比如疟疾、癌

症、和抗生素抗药性等。一篇相关的研究评述讨论了这项研究。

报告：Epochal Evolution Shapes the Phylodynamics of

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Interpandemic Influenza A (H3N2) in Humans, Katia Koelle, Sarah Cobey, Bryan Grenfell, and Mercedes Pascual

研究评述：Influenza Escapes Immunity Along Neutral Networks,

Erik van Nimwegen

2006 年 12月 22日 美国《科学》周刊 314卷 第 5807 期

一个新的细胞周期调控因子

Caulobacter crescentus 是湖泊和溪流中的一种貌不惊人的细菌。由于

只有一个很小的环状染色体和相对比较简单的结构，它已成为研究细菌怎样调

控细胞周期进度的一个很受欢迎的模型。Biondi 等人利用一种被称为

phosphotransfer profiling 的系统生物学方法（该方法可让研究人员快速确

定信号传导通道），识别出了一个以前未知的重要调控因子 ChpT，它在该细

菌中控制细胞周期主调控因子 CtrA。该研究还确定了所有主要细胞周期调控因

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子之间的联系，从而使研究人员首次有可能来定义一个分子网络，以解释细菌

细胞周期的进度。

Nature 444, 899-904 (14 December 2006)

FIGURE 1. Identification and in vitro reconstitution of two

phosphorelays controlling CtrA.

a, Phosphotransfer profiling20 of CckA. The purified kinase domain of CckA (CckA-HK) was autophosphorylated and mixed with each of the 44 purified response regulators and with 7 of the 27 receiver domains from hybrid histidine kinases encoded in the C. crescentus genome. Open arrowheads indicate lanes with high-efficiency phosphotransfer, manifested as loss of radiolabel from the CckA-HK~P band and/or incorporation of label on a response regulator or a receiver domain. b, Reconstitution of the CckA–ChpT–CtrA phosphorelay in vitro. Pluses and minuses indicate the presence or absence of reaction components. c, d, Phosphotransfer profiling of ChpT~P against (c) the 27 receiver domains of hybrid histidine kinases and (d) the 44 response regulators encoded in the C. crescentus genome. e, Reconstitution of the CckA–ChpT–CpdR phosphorelay in vitro.

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FIGURE 2. chpT encodes a histidine phosphotransferase that is

essential for viability and phenocopies ctrAts and cckAts.

a, chpT depletion strain (ML808: Pxyl–chpT) was grown to mid-log phase in xylose and then shifted to glucose or maintained in xylose. Growth (absorbance, A600 nm) and viability (colony forming units, CFU) were measured for up to 600 min. Pxyl–chpT cells grown in xylose accumulated CFUs at approximately the same rate as wild-type cells (data not shown). b, Morphology of chpT depletion strain grown for 6 h in xylose or glucose and compared to ctrAts (ctrAV148F) and cckAts (cckATS1) grown at 30 °C and 37 °C for 6 h. c, Levels of total CtrA protein and CtrA~P in the chpT depletion strain, grown in xylose, relative to a control strain bearing an empty vector. Error bars represent the mean s.d. from three independent experiments.

19

FIGURE 4. Schematic of cell cycle regulation in Caulobacter.

a, Diagram of the integrated genetic circuit controlling cell cycle progression and cellular asymmetry in Caulobacter crescentus. Biochemical relationships between components are colour-coded as indicated in the key. b, Summary of sub-cellular localization patterns for CckA, PleC, DivJ, CtrA~P, DivK and DivK~P during cell cycle progression. c, Summary of main feedback loops controlling CtrA activity and cell cycle progression.

GpMST1被克隆和定性

20

菌根真菌与植物之间的共生关系在陆地生态系统中至关重要，尤其是由聚

合菌（Glomeromycota fungi）形成的丛枝菌根（arbuscular

mycorrhiza）。真菌帮助植物吸收土壤养分，以换取碳水化合物，所以它们

构成一个很大的二氧化碳吸收体系。这种合伙关系的一个关键构成部分（碳水

化合物穿过共生界面的输送）的机制仍然不清楚，但现在

GpMST1（glomeromycotan monosaccharide transporter）已被克隆

出来，并被定性。这项工作是利用一种 glomeromycotan 菌（Geosiphon

pyriformis）与藻青菌所形成的独特共生体系完成的。在确定了这一重要分子

的性质后，就应有可能对丛枝菌根及其对碳流的贡献有更好的认识。

Nature 444, 933-936 (14 December 2006)

FIGURE 1. Comparison of bidirectional phosphate and carbon

exchanges.

21

Despite inverted relative dimensions of macro- and microsymbiont the interface and nutrient exchange in the G. pyriformis symbiosis correspond to that in the arbuscular mycorrhiza. Several arbuscular mycorrhiza-specific phosphate transporters (PT) are known from plants. The hypothetical role of GpMST1, and its orthologues, in the sugar uptake through the symbiotic membrane of glomeromycotan fungi is indicated together with the substrates of GpMST1 (fructose and putatively xylose are transported weakly).

FIGURE 2. The

G.pyriformis MST1.

a, The GpMST1 gene contains six introns. The splicing sites as well as the

22

UTRs are indicated; the SMART and CDS oligonucleotides at the cDNA termini (introduced by the cDNA library construction system used) carry the Sfi I restriction sites used for cloning; three poly(A)-signals were shown to be functional. b, The amino acid sequence and putative topology of GpMST1 are shown.

FIGURE 3. 14C-glucose uptake in GpMST1-expressing yeast strain

EBY.VW4000.

a, Substrate competition and colony growth (inserts) on the respective sugars; GpMST1 reconstitutes growth on glucose, mannose, galactose, and (very weakly) fructose; xylose is indicated to be transported but cannot be metabolized. b, Incubation in the presence of protonophores (CCCP,

DNP) and plasma membrane H+-ATPase inhibitors (DES, vanadate) for 5 min strongly inhibits glucose uptake. c, The pH optimum for uptake is about pH 7, in the yeast system. d, Michaelis–Menten kinetics of glucose uptake rates (pH 6.5) indicate a KM of 1.2 mM. Error bars represent s.d.; n = 3.

纳米颗粒控制微流体

在 2006 年 1月出版的《自然-材料学》上，Luke Lee 和同事展示了一种

用金纳米颗粒控制微流体的简单而灵活的方法。因为可应用于生物化学分析系

23

统和化学“芯片实验室”，微流体激起了科学家们极大的兴趣。传统上，控制

微型管道中的液体流动需要复杂的泵、阀门或模式表面。为了控制液体流动的

方向，Lee 的小组用低能激光加热纳米颗粒，让周围的流体蒸发。蒸汽在位于

流体前端的气-流界面间迅速凝固，并与原来的流体结合在一起，从而让液体

流动。 Lee 等表明，这种技术可用于活细胞在微流体管道中的传输，或者混合

两种液体。这种方法非常简单，因此可应用于生物化学分析中的大型集成微流

体线路等。

《自然-材料学》2006 年 1月

在实验室中观察细菌的进化

得益于完整的基因组序列，科学家们能够在实验室时间范围内观察细菌的

进化，这是 12月号的《自然－遗传学》期刊上的一篇论文报告的。对细菌进化

的实验研究历时多年，但是鉴别出导致可观察到的细菌生长特征变化的遗传变

24

化却非常困难，而且费时费力。采用NimbleGen 系统公司最近研制的一种新

方法，Bernhard Palsson 和同事能够快速、经济地测出基因组序列。他们在

介质中培育了一种大肠埃菌属，甘油是其中主要的碳和能量来源。研究人员在

44天的时间里培育出近 660代细胞，从 5 个种群中分离出单个的细菌。完整

的基因组序列让他们能够在实验结束时分离出来的细胞和开始使用的菌种之中

鉴别出 9 个不同的序列。在大肠埃菌属生物学中，部分变异比较容易理解，比

如负责编码甘油激酶的基因的变异，这种激酶在甘油断裂的第一步中起催化作

用。但以前的研究没有发现其它变异在甘油的新陈代谢中也发挥了作用，暗示

这种细菌在面对环境变化时的复杂反应。新方法有望提高我们在遗传水平对细

菌和有适度基因组的生物进化认识。

《自然－遗传学》2006 年 12月

胰岛素增敏新线索

25

脂肪组织（adipose tissue）主要由大量聚集成团的脂肪细胞构成，脂

联素(Adiponectin) 是脂肪细胞分泌的一种内源性生物活性多肽或蛋白质。以

前的发现，脂联素是一种胰岛素增敏激素(An Insulin-sensitizing

Hormone)，能改善小鼠的胰岛素抗性(Insulin resistance)和动脉硬化症；

对人体的研究发现，脂联素水平能预示 II 型糖尿病和冠心病的发展，并在临床

试验表现出抗糖尿病、抗动脉粥样和炎症的潜力。 今天，研究人员在 5月出版

的《自然－细胞生物学》上报告说，他们发现了一种调节脂联素的新化合物，

从而为研究脂联质功能和胰岛素敏感性机制提出了一种新途径。胰岛素是由胰

脏 β 细胞分泌出来的激素，主要功能是促进血液中的葡萄糖进入肌肉或脂肪组

织，提供人体所需的能量。当胰岛素不能发挥作用时，血液中的葡萄糖便无法

转化为人体所需的能量，导致血糖升高，糖尿病由此发生。而胰岛素抗阻是指

细胞不能有效利用胰岛素甚至对胰岛素的反应不再敏锐，这是造成糖尿病的最

主要原因。 科学家们相信游离脂肪酸和某些脂肪所释放的分子是引发胰岛素抗26

阻现象的罪魁祸首。 Lily Dong 和合作者一直在寻找与脂联素受体相关的蜂窝

状蛋白质，以期发现调节脂联素激素功能的新靶标。他们鉴别出一种多域蛋白

质，它能调节脂联素在脂肪酸氧化和葡萄糖吸收中的功能，并将这种新蛋白质

命名为 APPL1。他们的研究并进一步表明，在肌肉细胞中，APPL1 通过激酶

通道来调节脂联素的胰岛素敏感效应。

《自然－细胞生物学》2006 年 5月

压制艾滋病病毒

在 8月出版的《自然－结构和分子生物学》期刊上，研究人员报告了一种

人类抗体和一种在艾滋病病毒 I（HIV－1）表面发现的蛋白质之间的相互作用。

这种人类抗体名为 D5，它能识别控制 HIV-1融入宿主细胞膜过程的蛋白质的

中间形态。

为了进入宿主细胞，某些病毒必须首先与目标细胞表面粘合在一起，然后

27

再融化目标细胞的细胞膜。在 HIV-1 中，控制融合过程的蛋白质被称为

gp41，它在细胞膜融化过程中必须发生一系列的结构变化。这揭露出分子上

的一种“被保护区域”，它是一个理想抗体目标，因为它们序列的变化不太频

繁；即使对不同的 HIV 菌株来说，抗体“看”它们都是一样的。

Andrea Carfi 和同事报告说，人类抗体 D5 能识别 gp41 的中间结构。弄

清楚这些分子间的相互作用也许有助于科学家们开发出更有力的对付HIV-1

的抗体和治疗药物。因为其它病毒也会融化宿主的细胞膜，因此，将融化蛋白

质的中间态作为靶标有可能成为开发广泛适用的药物和疫苗的战略。

《自然－结构和分子生物学》2006 年 8月

老药发现新目标

肺结核是一种威胁全球健康的疾病，据估计每年有 2000万人死于这种疾

病。异烟肼是 50多年前开始使用的一种抗结核病药，也是人类第一批用于抗

28

结核的药物。如今，科学家鉴别出异烟肼抗击结核的一个新靶标，新发现将有

助于研制抗击肺结核的新成份。新研究结果发表在 5月出版的《自然--结构和分

子生物学》上。 过去的研究发现，异烟肼是通过与细菌上的一种酶来发挥作用

的，这种酶与细菌的细胞壁的形成有关，因此，异烟肼与这种酶的相互作用能

很快致细胞于死地。 Blanchard 和同事如今发现，异烟肼还攻击了结核病菌

生存的另一个关键过程。他们发现，异烟肼在工作过程中分解出的另一成分抑

制了一种名为 DHFR 的酶，这种酶是合成细菌核酸的重要因素。他们的研究进

一步展示了 DHFR 在异烟肼代谢过程中发挥抑制作用的细节。新发现有助于解

释临床中观察到的部分结核细菌出现抗药性的原因，也为基因工程设计新药提

供了新的基础。

《自然--结构和分子生物学》2006 年 5月

科学家发现分子差异能去除水稻中的杂草

29

红水稻是一种杂草，这种杂草会影响水稻的产量和品质，所以稻农非常

讨厌这些红水稻。但是由于红水稻和种植水稻属于同种，所以能杀灭红水稻的

除草剂同样也会杀死水稻。

现在美国国家自然基金（NSF）资助Washington 大学 St. Louis 分校的

植物进化学家 112万美元，进行一项为期 2 年的计划来研究两者之间的分子

差异，这能帮助稻农除去野草。这项计划叫做植物基因组比较测序计划。

Washington 大学的生物学助理教授 Kenneth M. Olsen说：“我们在寻

找造成两者之间差异的可能基因。而对这些差异了解越多就能更好的帮助控制

野草。这项研究最大优势在于我们掌握了种植水稻的整个基因组，所以能很方

便的寻找感兴趣的基因。”Olsen 和同事，Massachusetts 大学的 Ana

Caicedo，美国农业部的 Yulin Jia博士将测试两种假设。其中之一是红水稻是

由水稻野生化得来的，另一种是杂草从亚洲传入美洲然后杂交形成。

Olsen认为红水稻有很多野生物种的特征，他说：“通过对基因的分析，30

我们可以找到这些特征的起源，它们是否来自外来物种的杂交？或者是由水稻

去驯化得来？”

为了控制这种杂草，稻农想出了很多办法，其中一些能去除很大一部分的

红水稻，但是这些杂草种子能在土壤中存活 20 年，而且它们经常发生变异，

其中一些看起来和水稻没有区别，它们很难被区分出来。而Olsen希望这项研

究能帮助找到控制这些杂草的办法。

来源：教育部科技发展中心 发布时间：2006 年 12月 21日

负碳的生物燃料

研究显示，低肥力土壤上的高多样性的草地，比单一农业作物（比如玉米

或大豆），能产生更多的生物能量和更少的二氧化碳。为了减少对基于碳的燃

料的依赖，研究人员研究了食物、树木、和高肥力土壤种植作物的副产品的生

物燃料潜能。David Tilman 和他的研究小组调查了美国明尼苏达州被农业耕

31

作降低了养分、空置的贫氮沙质土壤上低输入、高多样性的本地品种混合草地。

他们在最多有 16种草种的 150多块地片中确定了生物能量的生产和生态系统

碳隔离量。他们报告说，来自这些多物种植物地片的生物燃料能提供负的净碳

量，因为这些地片的生态二氧化碳吸收量高于它们生产的生物燃料生产所释放

的碳量。

报告：Carbon-Negative Biofuels from Low-Input High-Diversity

Grassland Biomass, David Tilman, Jason Hill, and Clarence Lehman

2006 年 12月 8日 美国《科学》周刊 314卷 第 5805 期

新型 siRNAs 能够区分基因变异体Jesse Potash

新近完成的一项研究揭示了如何设计出高度特异性的小型干扰RNAs，

使得它能够区分出同一基因的相似变异体。

32

小型干扰RNAs(siRNAs)是那些能够减少目标 mRNAs 表达的小型

RNAs。近来，生物学家已经把 siRNAs 作为一种重要的工具投入到应用中 。

siRNAs也具有临床治疗的潜在意义，它可以作为治疗剂用于减少致病突变基

因的表达。但是，为了释放出 siRNAs全部的潜在功效，弄清楚目标特异性的

管理规则就变得非常之重要。一个主要的挑战就是要开发出 siRNAs，使它能

够区分出同一基因的两个相似变异体，这样以来，其中的一个基因变异体被剔

除，而其它的变异体则安然无恙。

近来，由美国马萨诸塞大学医学院的 Phillip Zamore、Zuoshang Xu 和

Neil Aronin 共同领导的研究小组，解决了这一问题。Zamore 回忆说：“开

始时，我不仅仅确信，很容易找到设计能区分基因变异体差异的 siRNAs 的规

则，而且我还认为对这些规则已经了解得相当多了。很显然，我这样想是错误

的。事实证明，这一工作比我想像得更难、更有趣。”

在他们大部分的研究工作当中，Zamore 将目标集中到了 SOD1 基因方面。33

SOD1 中单个碱基对的突变能导致家族性神经疾病肌萎缩侧索硬化症（ALS）

的出现。患有家族性 ALS 的个人经常同时携带有该基因的一个正常体和一个突

变体。因此，研究者在保持好该基因正常的功能与基因表达的同时，还渴望能

找到一种减少突变体 SOD1 表达的方法。作为完成这一目标的第一步，

Zamore 及其同事找到了一系列的 siRNAs来定位 SOD1。每种 siRNAs都在

不同的位置上把一个碱基对错配到野生型的 SOD1 上，但是，所有这些

siRNAs都完全与突变型 SOD1 相匹配。这些研究者希望，其中的一些

siRNAs 能剔除掉 SOD1.的突变体，但同时不对正常基因产生影响。

Zamore 及其同事通过系统检验这些 siRNAs，发现在 siRNA 中那个不匹

配的碱基对的位置对于选择性的建立是极端重要的；如果这种不匹配位于一些

特定的位置，该种 siRNA则无法有效地区别 SOD1 的正常体和突变体，这样

将会减少这两种 SOD1 的表达。一般来说，当不匹配位置不在该 siRNA 的

5'种子区，而且不匹配的最有效位置在该种 siRNA 的核苷位置 16时，他们能34

更好地进行区分。为什么这些不匹配现象在进行区分时比其它的类型更有效呢？

虽然人们目前并不完全清楚这一原因，但Zamore坚信，他们也许会影响某

一机制，通过该机制 siRNAs引起了目标退化：“我怀疑是这些不匹配通过

Argonaute蛋白阻碍了 mRNA裂解，但并没有同时阻碍目标 RNA 的束缚。从

某种感觉上讲，它们使得RNA诱导的沉默复合体（RISC）产生了无效束缚。

有趣的是，有迹象表明，核苷位置 16 对于植物性微型 RNAs 是重要的，它希

望哺乳动物的 siRNAs 通过在单个的磷酸二酯键上引导Argonaute蛋白进行

目标 mRNA 的裂解来起作用。因此，一旦这种 siRNA引导被限制到RISC 中

的 Argonaute蛋白上，那就必定在核苷位置 16 上存在着一些特殊的东西。”

在另一套试验中，这些研究者发现，两种嘌呤之间的这些不匹配对于区别两种

相似的基因突变体，比存在于单个嘌呤和单一嘧啶之间的一个不匹配表现得更

为有效。

除了对于 siRNA设计建立起重要的指导之外，这项研究也促成了高度特异35

性的 siRNAs 的建立，它对 ALS疗法非常有帮助。但是，Zamore 提醒说，

“对于 ALS来说，运输问题依然是一个巨大的障碍，因此我无法预测还需要

多长的时间，我们才能将 siRNAs引入治疗过程之中，来对付这一恐怖的疾

病。”

Nature Methods 3, 876 (2006)

生物柴油生产现状及技术进展

生物柴油由未使用过的或使用过的植物油（可食用和不可食用的）与动物

脂肪，通过各种化学过程生产，最常见的是反酯化法。由三甘油酯（所有天然

油和脂肪的主要成分）生成甲酯、乙酯或较高级的醇酯。三甘油酯与醇类在催

化剂存在下生成脂肪酸酯，脂肪酸酯的物化性质与石油基柴油相似。

柴油分子由 15 个烃链组成，植物油分子一般由 14~18 个烃链组成，与

柴油分子相似。因此，用菜子油等可再生植物油或动物脂肪可加工制取新型燃

料—生物柴油。生物柴油合成采用比较简单的酯基转移反应（反酯化），只需36

油、醇和催化剂，醇类现多选用甲醇，可使植物油与醇类生成酯类并联产丙三

醇（甘油）。反酯化工艺基于碱催化或酸催化，碱催化反酯化优于酸催化，过

程转化率高（大于 98%），在常压（0.14MPa）和低温（～66℃）下进行，

可直接转化无中间步骤。油的分子是三甘油酯，含有 3 个脂肪酸链，联结于甘

油分子骨架上。催化剂一般采用氢氧化钠，催化剂用量为植物油的~1m%。催

化剂的作用是使链断开并与甲醇反应生成甲酯，副产甘油（丙三醇）。

    世界各国生产生物柴油所用的原料不尽相同，美国使用大豆籽和动物脂肪，

欧洲使用油菜籽和动物脂肪，日本使用动物脂肪，马来西亚使用椰子油籽，印

度使用非食用植物油。欧洲和北美利用过剩的菜子油和豆油为原料生产生物柴

油获得推广应用。

     生物柴油优点： 与矿物柴油相比，生物柴油具有环境友好特点，其柴油车

尾气中有毒有机物排放量仅为 1/10，颗粒物为 20%，CO2 和 CO排放量仅

为 10%。按照京都议定书，欧盟 2008～2012 年间要减少CO2排放 8%，就37

燃料对整个大气CO2影响的生命循环分析（LCA）指出，生物柴油排放的

CO2比矿物柴油要少约 50%。

    生物柴油通常可与石油基柴油调合使用，现一般调入 20%。调合油的效益

是：含硫很低（0～24PPm）、高十六烷值（46～70，如采用加氢裂化工艺

为 100）。调合油甚至优于欧Ⅳ柴油。生物柴油可大大减少未燃尽烃类、CO 和

颗粒物质排放。调合 20%生物柴油的调合油，可减少排放如下：总的未燃尽烃

类 20%、CO12%、颗粒物质 12%、硫酸盐 20%、多环芳烃 13%、硝化多环芳

烃 50%、特定烃类的潜在臭氧量 10%。生物柴油为清洁燃料，几乎不含硫、无

芳烃、含氧约 10%（有助于充分燃烧）。柴油机无需改造，不像其他替代燃料

如CNG、LNG 和乙醇调合油需改造发动机。另外，可改进润滑性，生物柴油的

长链脂肪酸的酯类是喷射系统极好的润滑剂。石油基柴油脱硫过程也大大损害

了润滑性（特别是含硫从 500PPm减少到 50/10PPm）。加入极少量（1～

2%）生物柴油的调合油就可使润滑性提高提高 65%。 38

     各国生物柴油的应用情况 欧盟最近发布了两项新的指令以推进生物燃料

在汽车燃料市场上的应用，这将进一步推动欧洲生物柴油工业的发展。与常规

柴油相比，生物柴油价格要贵一倍以上，为此，指令要求欧盟各国降低生物柴

油税率，并对生物柴油在欧洲汽车燃料中的销售比例作出规定。这将有助于欧

洲生物柴油市场价值由 2000 年 5.04亿美元提高到 2007 年 24亿美元，年

增长率可望达到 25%。

    德国现有 8 家生物柴油生产厂，拥有 300多个生物柴油加油站，2003 年

生产生物柴油 50万吨/年，不久将达到 90万吨/年。并制定了生物柴油标准

DIN V51606，对生物柴油不收税。

    法国有 7 家生物柴油生产厂，总能力为 40万吨/年。使用标准是在普通柴油

中掺加 5%生物柴油，对生物柴油的税率为零。意大利有 9 个生物柴油生产厂，

总能力 33万吨/年，对生物柴油的税率为零。奥地利有 3 个生物柴油生产厂，

39

总能力 5.5万吨/年，税率为石油柴油的 4.6%。比利时有 2 个生物柴油生产厂

总能力 24万吨/年。

    英国生物燃料公司在英国锡尔圣兹投资 2100万英镑（3780万美元）以豆

油为原料建设生物柴油装置，该装置能力为 25万吨/年生物柴油、1.96万吨/

年医药级和 2700吨/年工业级甘油，以及 600吨/年硫酸钾化肥。该装置于

2005 年 1季度投产。生物燃料公司还计划在当地于 2005 年再建第二套装置，

使生物柴油能力翻番，达到 50万吨/年。该公司另计划于 2007～2009 年在

英国或欧洲其他地区再建三套装置，总能力为 75万吨/年。

    芬兰能源公司富腾（Fortum）公司 将在芬兰南部城市波尔沃建设专门生

产生物柴油的加工厂。这座耗资 1亿欧元的生物柴油加工厂将于 2007 年夏季

投产。该加工厂从植物油和动物脂肪中提炼高质量的柴油，预计每年可生产生

物柴油 17万吨。这种生物柴油可供各种以柴油作燃料的机动车辆使用，可减

少汽车的废气排放量。 40

    欧洲其他国家的生物柴油生产量为：捷克和斯洛伐克 10万吨/年。

    由于用于加工生物柴油的植物油是可更新的原料，在欧盟鼓励其成员国增

加使用可更新原料的情况下，欧盟成员国对生物柴油的需求量今后将会进一步

增加。

    目前，美国有 4 家生物柴油生产厂，总能力为 30万吨/年。在普通柴油中的

掺入量为 10%～20%。生物柴油的税率为零。美国 GreenStar 产品公司所属

子公司美国生物燃料（ABF）有限公司正在加利福尼亚州建设美国最大的生物

柴油生产装置，设计生产能力为 3500万加仑/年（约 12万吨/年）。为了减少

装置的占地面积及投资和操作成本，该装置采用连续流动工艺。在装置的建设

中，使用ABF拥有专利权的单元反应器/分离器，每个单元反应器/分离器的生

产能力为 250万加仑/年，这种单元组件安装非常方便，可以根据市场需求的

情况来进行扩能。该装置己于 2003 年开始进行生物柴油生产。

41

    巴西生物柴油法令 LEI No.11097巳获通过，2008 年 1月起正式推行。B-

2 柴油（2%生物柴油/98%常规柴油）于 2008 年 1月起执行，B-5 柴油

（5%生物柴油/95%常规柴油）标准也巳颁布。

    亚洲国家也在兴起生物柴油产业。马来西亚产能为 50万吨/年。日本生物柴

油生产能力达到 40万吨/年。泰国发展生物柴油计划于 2001 年 7月发布，泰

国石油公司承诺每年收购 7万吨棕榈油和 2万吨椰子油，实施税收减免，泰

国第一家生物柴油装置已经投运。

    据美国 Freedonia咨询公司研究分析，生物柴油需求将快速增长，到

2006 年增速为 30%，生物柴油市场价值将从 2003 年 3500万美元增长到

2006 年 1.3亿美元。

     生物柴油的生产技术进展 新开发的生产生物柴油的反酯化方法可克服碱

催化反酯化的缺点，如甘油回收和催化剂脱除困难、反应不完全，以及当油中

42

含有游离脂肪酸和/或水时会生成皂化产物。传统的碱催化方法从三甘油酯和甲

醇生产脂肪酸甲酯存在几个问题，包括在室温下反应速率太慢。植物油的催化

反酯化（特别是反甲基化）生产生物柴油甲酯过程很慢，这是因为初期反应混

合物由两相组成，因此反应受到传质限制。生物柴油的工业化生产作为石油基

柴油的替代路线往往还不甚经济，因为其生产费用为石油基柴油的约 3倍。现

在的生物柴油生产商仍采用高压、高温方法，速度慢且能耗高；采用化学方法

也不能低成本地生产达到ASTM 标准的生物柴油。加拿大 BIOX公司正在将

David Boocock公司开发的技术（美国专利 6642399 和 6712867）推向

工业化，该工艺不仅可提高转化速度和效率，而且可采用酸催化步骤使含游离

脂肪酸高达 30%的任意原料（包括大豆油、废弃的动物脂肪和回收的植物油）

转化为生物柴油，该工艺可降低生产费用高达 50%，如果商业化成功，可望

使生物柴油生产费用与石油基柴油相竞争。BIOX公司自 2001 年 4月起己在

加拿大奥克韦尔（Oakville）100万升/年中型装置上验证了称为 BIOX 的工43

艺，现正在 Hamilton Harbour 生产地投资 2400万美元建设 6000万升/年

生物柴油装置放大 BIOX 工艺，该装置于 2005 年 6月投运，这将是 BIOX公

司第一套工业化装置。在 BIOX 工艺中，脂肪酸首先在酸催化反应中转化成甲

酯，反应在接近甲醇（溶剂）60℃的沸腾温度下，在柱塞流反应器（PFR）

中进行，40 分钟反应后，在相似条件下，在第二台 PFR 中采用专用的共溶剂

进行碱催化反应，三甘油酯在几秒内就转化成生物柴油和丙三醇副产物，

99.5%以上未使用的甲醇和共溶剂循环利用，回收冷凝潜热用以加热进料。

    新开发的方法使用共溶剂，可形成富油单相系统，因此反应可在室温下快

速进行，10 分钟内反应可完成 95%，而现用工艺要几个小时。该工艺已在德

国莱尔（Leer）8万吨/年验证装置上应用，第二套 10万吨/年装置也在德国

汉堡投运。

    在新工艺中，惰性的共溶剂使之形成富油、单相系统，整个反应在该系统中

进行，因此可提高传质和反应速率。碱催化步骤在接近室温和常压下于几分钟44

内完成，它与酸催化步骤结合在一起，使BIOX 工艺可连续进行。BIOX 工艺

还克服了生物柴油现有生产路线的另外一些缺点，包括必须使系统达到所需纯

度，以免反应中断，以及它们不能处理含脂肪酸大于 1%的物料。使用常规技

术生产生物柴油的成本因原料而变化，原料占生物柴油生产费用约

75%~85%，因此采用低费用的原料达到高的转化率至关重要。

    Diester 工业公司在法国塞特建设生产脂肪酸甲酯（FAME）的新装置，

16万吨/年的装置将于 2005 年底投产，这将是采用Axens公司 Esterfip-H

工艺的第一套工业化装置。塞特装置的建设符合欧盟指令 2003/EC3117 目标

要求，该指令要求到 2010 年使生物燃料用量达到 5.75%，生物燃料可减少

温室气体总排放量和使欧盟减小对原油进口的依赖。生物柴油的主要组分

FAME 通过植物油如菜子油、大豆油和葵花子油来生产。Esterfip-H 工艺由法

国石油研究院（IFP）研发，由 Axens公司推向商业化。第一套工业化

Esterfip 工艺装置于 1992 年建于法国 Diester 工业公司维尼特地区，基于均45

相催化剂。而新装置则采用多相催化剂—两种非贵金属的尖晶石混合氧化物，

属首次应用，它可避免采用均相催化剂如氢氧化钠或甲醇钠的工艺所需的几个

中和、洗涤步骤，以及不会产生废物流。此外，来自 Esterfip-H 工艺的丙三醇

副产物的纯度大于 98%，而采用均相催化剂路线时，其纯度约为 80%。这种

副产物的利用可提高整个生产的经济性。在连续法 Esterfip-H 工艺中，反酯化

反应采用过量甲醇在比均相催化剂工艺温度较高的条件下进行，过量甲醇用蒸

发方法除去，并循环至工艺过程，与新鲜甲醇相混合。该化学转化采用两个串

联的固定床反应段来达到，分离丙三醇以改变平衡。每一反应器后的过量甲醇

通过部分闪蒸除去，酯类和丙三醇再在沉降器中分离。生物柴油在甲醇最后回

收后通过减压蒸发予以回收，然后提纯去除微量丙三醇。甲酯纯度超过 99%，

产率接近 100%。

    再一先进的工艺是在连续流动反应器中采用油与甲醇强化混合，2002 年采

用这一技术的 10×104t/a 生物柴油装置己建于德国玛尔（Marl），从该过程46

可回收 1.2万吨/年高级丙三醇。该技术也在美国加州里弗代尔（Riverdale）

南方动力公司的 10万吨/年装置上应用。

    另一创新工艺是采用连续反酯化反应器（CTER），这一新技术可降低投资

费用，Amadeus公司在澳大利亚西部建设的 3.5×104t/a 生物柴油装置将采

用CTER 技术。

    目前生物柴油主要采用化学法生产，现正在研究生物酶法合成生物柴油技

术。用发酵法（酶）制造生物柴油，混在反应物中的游离脂肪酸和水对酶催化

剂无影响，反应液静置后，脂肪酸甲酯即可分离。日本大阪市立工业研究所成

功开发使用固定化脂酶连续生产生物柴油，分段添加甲醇进行反应，反应温度

为 30℃，植物油转化率达 95%，脂酶连续使用 100天仍不失活。反应后静置

分离，得到的产品可直接用作生物柴油。

47

    通过加氢裂化方法也可生产生物柴油，现已开发了几种新工艺。加氢裂化方

法不联产丙三醇。可将植物油转化为高十六烷值（~100）、低硫柴油，可加工

宽范围原料包括高含游离酸的物料。加氢裂化过程中发生几种反应，包括加氢

裂化、加氢处理和加氢。产率为 75%～80%，十六烷值高（～100），硫含量

<10PPm。28天后可生物降解 95%，而石油基柴油在同样时间内降解 40%。

与其他生物柴油比，主要优点是可降低NOx排放。该工艺采用常规的炼厂加

氢处理催化剂和氢气，可供炼油厂选用，因有氢气可用，可方便地与炼油厂组

合在一起。

     我国开发现状 目前我国生物柴油的研发和生产已经起步。

    2002 年 8月，四川古杉油脂化学公司成功开发出生物柴油，该公司以植物

油下脚料为原料生产生物柴油，产品的使用性能与 0号柴油相当，燃烧后废物

排放较普通柴油下降 70%，经检定，主要性能指标达到德国 DIN 51606 标

准。 48

    2002 年 9月，福建省龙岩市也建成 2万吨/年生物柴油装置，标志着我国

生物柴油生产实现了产业化，其产品成本可控制在 2000元/吨，该市并于

2003 年建成 10万吨/年能力。这种利用废动植物油生产生物柴油的新工艺在

福建龙岩卓越新能源公司应用以来，截至 2003 年 5月，已生产生物柴油

5000多吨。产品经上海内燃机研究所试验测定，其技术性能指标优于 0#矿物

柴油。由福建省经贸委组织的专家鉴定认为，这一生物柴油技术具有较高的推

广和应用价值。生物柴油项目已被福建省列为 2002 年重点技术创新项目。

    制约生物柴油产业化最大的障碍是成本过高，而福建省研制成功的这一技

术克服了生物柴油成本高的难点。主要取决于两点：①这一工艺的原料是废旧

的植物和动物油，价格低且来源广。主要有：食用油加工过程中的下脚料，仅

国内食用油厂一年就有这样的下脚料 200万吨；宾馆、食堂中的“地沟油”

（又称“泔水油”），一般的大中城市都有人专门回收这种“地沟油”；粮食

储备的陈化油；废猪油、鱼片油等动物油。这一生物柴油所需要的原料，全国49

每年有 400万吨，但目前这些“原料”大都作为废物处理，不仅容易污染环

境，而且造成很大浪费。②新工艺在两项关键技术上取得突破。通过一种微酸

性催化剂技术，使得在同一反应罐中醇解和酯化可同时进行，且反应速度明显

加快。通过一种金属盐处理剂，解决了利用废旧动植物油脂生产柴油残留酸值

高的关键问题。这两项关键技术均明显降低了成本。鉴定认为这两项关键技术

达到了国际先进水平。

    卓越新能源公司投产的 2万吨/年生物柴油项目，总投资 1200万元。2003

年每吨生产成本约为 2100元，通过石油公司的销售渠道进行销售，市场售价

每吨 2700元，略低于矿物柴油市场上每吨 2800元的售价，但扣除税收等因

素，每吨可实现利润 400～500元。这种生物柴油既可以单独使用，也可以和

矿物柴油混用。另外，除了成本低之外，这一工艺在生产过程中不会产生二次

污染。

50

    清华大学完成的生物酶法转化可再生油脂原料制备生物柴油新工艺通过教

育部鉴定。利用这项创新工艺制备的生物柴油样品经检测，关键技术指标符合

美国及德国生物柴油标准，并符合我国 0号优等柴油标准，这种环境友好的生

物酶法生物柴油技术将有望实现产业化。

    目前已实现产业化的生物柴油生产工艺主要是化学催化转酯法。但化学法制

备生物柴油存在一些不可避免的缺点，如反应过程中使用过量的甲醇，后续处

理过程较繁琐，油脂原料中的水和游离脂肪酸会严重影响生物柴油得率及品质，

废碱（酸）液排放容易对环境造成二次污染等。而利用生物酶法合成生物柴油

由于具有反应条件温和、醇用量小、无污染物排放等优点，日益受到人们的重

视。但利用生物酶法制备生物柴油目前存在着一些亟待解决的问题，如反应物

甲醇容易导致酶失活、副产物甘油影响酶反应活性及稳定性、酶的使用寿命过

短等，这些问题成为生物酶法工业化生产生物柴油的主要瓶颈。针对生物酶法

工艺瓶颈问题，清华大学课题组提出了全新的生产工艺，从根本上解除传统工51

艺中反应物甲醇及副产物甘油对酶反应活性及稳定性的负面影响，酶的使用寿

命显著延长。利用该新工艺生产生物柴油，操作简单，常温常压下可将动植物

油脂有效转化成生物柴油，产率达 90％以上。另外，在该新工艺中，脂肪酶

不需任何处理就可直接用于下一批次反应，并且表现出相当好的操作稳定性。

该新工艺已在反应器上连续运转了 10 个多月，近 200 个反应批次，酶反应活

性未表现出任何下降的趋势。新工艺显著延长了酶的使用寿命，大大降低了酶

的使用成本，有望采用环境友好的生物酶法实现生物柴油的产业化生产。

    由科技部组织实施的农产品深加工重大科技专项'双低油菜籽深加工关键技

术研究与开发'课题组，围绕以油脚等废弃油脂开发生物柴油转化技术进行联

合攻关，取得重大技术进展。针对现有废弃油脂制备生物柴油存在原料适应性

差、工艺复杂、转化利用率低以及能耗较高等问题，该课题组在国内外首次提

出了共沸蒸馏甘油酯化—甲酯化生物柴油转化技术，并在此基础上先后完成了

废弃油脂的收集和技术测试、废弃油脂的生物柴油转化工艺研究、酯化专用关52

键设备研究、扩大试验、产品技术指标测试和应用试验等。试验及测试结果表明：

采用共沸蒸馏甘油酯化—甲酯化新技术实现了废弃油脂游离脂肪酸酯化和油脂

转酯化高效反应，产品各项指标达到美国 ASTM6751 标准，使用性能良好，

完全能够作为柴油内燃机燃料。2004 年该技术通过湖北省科技厅组织的成果

鉴定。与国内外现有同类技术相比，该工艺技术具有工艺简捷，原、辅料消耗

低，产品收率高等显著技术特点，达到国际先进水平。该技术将废弃油脂转化

成生物柴油，实现了资源的综合利用，有利于实现农业和能源产业的有机结合，

有利于环境保护，具有良好的经济和社会效益。目前我国油脂消耗量高达

1700万吨，每年要产生 250多万吨的废弃食用油脂，通过该技术加以转化

可以实现产值 105亿元，增值可达 40亿元。

    采用新工艺在中试装置上生物柴油产率达 90％以上。用中试装置生产的生

物柴油样品经中国石化集团石油化工科学研究院检测，产品技术指标符合美国

及德国的生物柴油标准，并满足我国 0号优等柴油标准。中试产品经发动机台53

架对比试验表明，与市售石化柴油相比，采用含 20％生物柴油的混配柴油作

燃料，发动机排放尾气中一氧化碳、碳氢化合物、烟度等主要有毒成分的浓度

显著下降，发动机动力特性等基本不变。生物酶法因反应条件温和、醇用量小、

无污染物排放等优点日益受到重视，但存在甲醇及副产物甘油影响酶的反应活

性及稳定性、酶的使用寿命不长、成本高等问题，成为生物酶法工业化生产生

物柴油的瓶颈。对此，清华大学化工系再生资源与生物能源试验室提出了一条

全新的生产工艺路线，可以有效消除甲醇及副产物甘油对酶反应活性及稳定性

的负面影响，酶的使用寿命也随之大大延长。该工艺在湖南海纳百川生物工程

有限公司 200千克／日的生物柴油中试装置上得到成功应用，以菜籽油为原

料生产出生物柴油。中试装置的反应器连续运转 3 个多月，生物酶活性未表现

出明显下降趋势。另外，利用目前已有的技术还可以将生物柴油生产过程中的

副产物甘油进一步转化为高附加值产品 1，3－丙二醇。两项技术的有机结合，

可以显著提高生物柴油生产过程的经济效益。 54

生物柴油产业是新兴的高新科技产业，我国“十五发展纲要”己明确提出

发展各种石油替代品，并将发展生物液体燃料确定为新兴产业发展方向，加快

我国生物柴油的研发和应用是新时期赋予我们千载难逢的发展机遇。

中油网：2006-11-29 10:06

美国拟创建生物能源中心

美国能源部将要耗资 2.5亿美元建立两所新的生物能源研究中心。

秘书处的 Samuel Bodman说建立生物能源中心将要加速能源的基础研究，

开发纤维素乙醇和其他的生物燃料。

在周三参观伊里诺斯州的 Channahon途中，Bodman说：“实施这一计

划对于我们将要实现在 2030 年要用生物燃料代替 30％的运输燃料是一个很

重要的步骤。这些生物中心的任务就是加速研究进程，使得有效的生物燃料代

替化石燃料的计划取得重大突破。”55

今年全球生生产了四十亿加仑的乙醇，其制造原料来源于玉米。到 2012 年

估计每年要制造出至少 75亿加仑的可更新燃料来满足全球燃料市场的需求。

一些大学，国家实验室，非盈利性机构团体和一些私人公司都在竞争建立

这个生物能源中心。能源部最终要根据科学同行的一些评价来于明年夏天宣布

结果。这些中心将于 2008 年开始工作，2009 年开始完全运转。

来源：教育部科技发展中心 发布时间：2006 年 8月 7日

生物燃料热背后的事实

生物燃料是当今的热门话题，在媒体报道中占突出地位，在股票市场上也

吸引着大量资金。但这种热度在多大程度上是有根据的呢？这是否只是一种宣

传呢？在本期的一篇长达 11页的 Business News Feature 文章中，Nature

记者揭示了生物燃料热背后的事实。

Nature 444, 669 (7 December 2006)56

转载几篇相关的文章，供参考。

Green shoots of growth

Abstract

Energy from biomass is an idea whose time has returned.

Until the twentieth century, biomass was humanity's principal source of energy, heating our stoves and feeding our draught animals. Even today, roughly 10% of all our energy comes from biomass — far more than from any other renewable energy source or, for that matter, from nuclear fission.

But this use of biomass for energy supply is accompanied by many challenges (see page 669). For one thing, it is often not all that renewable — the biomass sources that provide firewood to the world's poor, for example, are not being replanted. For another, it is very inefficient: gathering firewood takes a long time. The history of the past couple of centuries has been in large part one of people moving away from biomass as soon as they can afford to do so.

Three recent developments have spurred renewed interest in biomass, however. One is the need to reduce greenhouse-gas emissions. The requirement for other external energy inputs during biomass processing means that it often involves some net carbon emissions — but the amount of carbon dioxide given off by burning biomass is the same as that taken from the atmosphere by photosynthesis in the first place. If biomass projects could sequester carbon, either by enriching the soil beneath plantations or by storing any carbon dioxide produced in combustion, they could even be carbon negative — a unique selling point for this energy source.

The other two developments are the upward movement in the prices of oil and natural gas, and the related revival of concerns about the security of their supply. Most nations are seeking home-based energy sources that do not rely on political stability in the Middle East or Russia.

57

It seems unlikely that these factors will provide sufficient impetus to propel biomass energy to the very front rank of possible alternatives to fossil fuels. But biomass clearly has a potential role as part of a portfolio of energy sources for the twenty-first century.

If that role is to be fulfilled, two things need to happen. Nations have to build regulatory mechanisms that recognize the carbon benefits of technologies such as biomass — through emissions pricing, a carbon tax or a combination of the two. And intensive research needs to be conducted into both the efficient production of biomass and its conversion into useable energy.

Biomass is likely to benefit poorer countries, which tend to be in tropical areas where plants grow quickly.

One focal point for such research should be finding ways to grow biomass quickly and in an easily processed form while minimizing external inputs, such as fertilizer and pesticides. Another is the systems engineering of farms and ecosystems, finding ways to fit biomass projects into and around present land use and possible changes in farming practice.

A major attraction of biomass is that it is likely to benefit poorer countries, which tend to be in tropical regions where plants grow quickly. There is plenty of scope for more collaboration between developing countries on biomass research and development, both to meet local needs and for export.

But this requires consideration of the local and global ecological impact of biomass expansion. Vast tropical monocultures eating away at primary forests — as exemplified by the production of palm oil in Indonesia — will benefit no one, except those who profit from selling the fuel. In effect, such approaches take green subsidies from richer countries, and use them to despoil the tropics.

Similar problems afflict existing biomass programmes in the United States, where ethanol refineries often burn fossil fuel and are reliant on subsidized corn monoculture. More innovative approaches would include firing the refineries with agricultural waste, and feeding them with plants of many different species. Biomass energy should be developed energetically, but within the context of appropriate environmental policies, and using approaches that are both sustainable and cost-effective.

58

Nature 444, 654 (7 December 2006)

Introduction: Biofuelling the future

J. BLAIR/CORBIS

The idea of using living plants as a way to capture the all-but-unlimited energy of the Sun has a powerful romantic attraction. Unfortunately, plants have a basic problem in this respect. Compared with, say, an array of solar cells, they are strikingly poor transducers of the Sun's energy; even an intensively managed plantation struggles to store away more than a watt or two per square metre on average.

But plants have advantages that, in some circumstances, outweigh their low efficiency. For a start, unlike solar cells, plants are very cheap to make; indeed, with a moderate supply of water and nutrients they will make themselves. They use up carbon dioxide in the process, which is a definite environmental plus — and they turn that carbon, along with the Sun's energy, into stable organic compounds.

This means that the Sun's energy is made available at a later date when the Sun isn't shining. And it means that it can be processed, at some cost and effort, into hydrocarbon fuel of the sort that today's cars, trucks and planes can handle with relatively little modification. To governments worried about the stability of their fuel imports, or indeed the long-term future of global oil production, that could matter quite a lot.

So although their inefficiency means that plants will never be the total answer to our global energy problems, they have substantial potential as a source for carbon-neutral fuel for the ever-thirsty transportation sector, as long as oil prices stay reasonably high.

Our Features this week look at this potential in three different areas. The first (see page 670) addresses the world's most substantial biofuel success — the

59

Brazilian sugar-cane ethanol industry — and assesses its impact and potential. The second (see page 673) looks at the possibilities of making ethanol, or other alcohols, out of sources of cellulose from farm waste to poplar plantations — possibilities currently entrancing US entrepreneurs.

The third feature (see page 677) looks at a different approach to alternative fuels — the thermochemical route. This technology can be used to make fuel from biomass — but it can also, more easily, be used to make liquid hydrocarbons from solid coal, and this is where most research in the area is focused. For countries that have a lot more coal than oil, this coal-to-diesel technology can look attractive purely on an energy-independence basis. But without careful and costly sequestration of the carbon dioxide produced, it would be a significant additional source of greenhouse gases.

No fuel technology is perfect. But, as we argue in our Editorial (see page 654), a greenhouse-gas crisis and worries over oil supply mean that diversifying the range of options makes good sense — as does the development of new routes from research to large-scale deployment.

Nature 444, 669 (7 December 2006)

Sugar cane and ethanol: Drink the best and drive

the rest

Emma Marris1

Brazil's sugar-cane ethanol industry is the world's best and able to get better, says Emma Marris.

PAULO WHITAKER/REUTERS

Cleaning up: Brazil's use of sugar cane, here being washed for refining, significantly reduces CO2 emissions.

60

In Brazil, alcohol made from sugar cane is mixed with lime juice and a little of the cane sugar itself to make caipirinhas — and it's a fine way to get the weekend off to a flying start. But come Monday morning, sober Brazilian commuters are still using cane liquor — in their fuel tanks. Most Brazilian petrol is gasohol, which by government mandate is currently 23% ethanol. Next to the gasohol pumps at the petrol stations are pumps that offer pure ethanol.

Ethanol from sugar cane has been powering cars in Brazil on and off since the 1930s, and with government backing since the OPEC price rises in the 1970s. It makes fairly obvious sense. Brazil's tropical sun makes it a great place for growing sugar cane: it is the largest cane producer in the world, producing more than twice as much as the number two, India. Just crush out the sucrose solution, ferment it into alcohol with the help of yeast and distill it to the desired concentration; burn the 'bagasse' — the fibrous pulp left over when the sugar is squeezed from the cane — to power the process along. Put the alcohol into your gas tank and you are effectively driving it on sunlight.

In the past few years, Brazil's bioethanol industry has sprouted new wings thanks to higher petrol prices and 'flex-fuel' cars, which can sense different mixtures of petrol and ethanol and adjust their workings accordingly. Introduced to the mass market in 2003, these cars changed everything; flex-fuel vehicles now account for well over half of Brazil's new cars. Their attraction is that they allow the owner to trade off continually between the advantages of neat ethanol — which gives 20% to 30% fewer kilometres to the litre — and gasohol depending on the current prices and the local tax rates. (Tax alone means that if you were to take a road trip across Brazil, you'd switch back and forth a couple of times as you crossed from state to state.)

Sweet solution?

Flex-fuel cars have created an expanded home market for Brazil's ethanol, and production is up. The country produced 282,000 barrels (45 million litres) a day in 2005, up from 192,000 in 2001. The ministry of agriculture is projecting 442,000 barrels a day by 2010. Oil is still very much ethanol's big brother, and in the first part of 2006 the country was producing an average of more than 2 million barrels a day while consuming a bit more. But 40% of

61

the fuel powering Brazil's cars is home-grown ethanol. The sugar cane industry supports more than a million jobs, in a country with an unemployment rate of 10%. Some bagasse-powered mills sell surplus power back to the grid. And although the carbon put into the atmosphere by petrol-powered cars comes out of fossil reserves, the carbon from ethanol is carbon that was in the atmosphere just a couple of years ago, before the sugar cane got hold of it and worked its photosynthetic miracle. There are thus, in principle, no net emissions.

This all sounds a bit like a free lunch, or at least a free ride, and everyone knows they don't exist. Growing sugar cane, harvesting it, fermenting and distilling it and then distributing it is a complex business. It uses inputs — fuel for harvesters, nitrogen fertilizers for the cane — that themselves require energy from elsewhere. And it has potentially damaging side-effects, such as soil erosion and the emission of nitrous oxide, a greenhouse gas, from farmland. Taking all the complexities into account, is ethanol still as good a deal as it seems? And if it is, how much of this good thing can Brazil — and the rest of the world — get its hands on?

In 2004, Isaias de Carvalho Macedo at the University of Campinas did a study for the state of São Paulo that considered energy inputs such as fertilizer manufacture and agricultural machinery in the sugar-cane industry1. He and his colleagues estimate that the whole shebang costs about 250,000 kilojoules per tonne of cane. That tonne of cane in turn yields about 2 million kilojoules in ethanol and surplus electricity made by burning bagasse. That's

an eight-fold return.

This is a lot better than ethanol-makers in the United States manage, and the reason is clear to anyone who's ever strolled through a cane field chewing on a bit of the stuff; cane is a far more prolific plant than corn (maize), from which the United States makes almost all its ethanol, and it puts a great deal of its — or rather the Sun's — energy into making sugar.

What's more, sugar cane needs less by way of inputs, and in the parts of Brazil where most of it is grown at the moment it needs no irrigation. It

62

needs only to be ploughed up and replanted every five years; between times it can be cropped repeatedly and will simply grow back, although the yields drop a bit with each harvest. For all these reasons, sugar-cane ethanol is also currently the cheapest ethanol to produce in the world. A litre costs about 25 cents to make. The commodity price for anhydrous ethanol (the kind mixed into gasohol) is about 27 cents.

Because of this a lot of money is pouring into the centre-south region of Brazil, where the sugar cane grows best. But that does not necessarily mean that investors believe Brazilian cane ethanol is sure to become the planet's biofuel of choice. A range of other emerging liquid-fuel technologies, including biodiesel, butanol, coal to liquid, and the buzz leader at the moment, cellulosic ethanol (see page 673), are attracting investment around the world, too. And the investors are typically backing a range of possibilities while they wait to see how the market pans out.

Arnaldo Vieira de Carvalho, an energy specialist at the Inter-American Development Bank in Washington DC, sees current investment in bioethanol as, among other things, a way of building up a better stake today for whatever the most impressive biofuel technology turns out to be tomorrow. "If you now put your money in distilleries, in five years you have made your money," says de Carvalho, "and then you put your investment in the technology that is coming."

Fuelling change

As the rest of the world gets interested in ethanol, both as a fuel in its own right and as a fuel additive (to replace methyl tertiary-butyl ether, or MTBE, an anti-knocking additive that is on its way out for environmental reasons), Brazil is ramping up exports (see 'Key companies'). Brazilian manufacturers are actively promoting ethanol distribution systems in other countries. Petrobras, until the 1990s the state oil monopoly and still the biggest player in Brazilian oil, is planning to build an ethanol pipeline from the centre to the south, out to the ports. It will be the first of its kind. Pipelines for ethanol have long been considered problematic, as it tends to absorb moisture and impurities as it flows. Construction will start in January, according to Plinio Mario Nastari, president of Datagro in São Paulo.

63

Not all foreign markets are easily tapped. Increasing Brazilian ethanol imports to the United States led the United States to slap on a tariff of 14 cents per litre (54 cents per gallon), to protect its highly subsidized corn ethanol makers. One effect of this has been to put Jeb Bush, Florida's governor, at odds with his brother President George W. Bush; the governor would rather buy cheap ethanol from Latin America than expensive stuff from the Midwest.

R. HODGKINS

Environmentalists are watching all this expansion carefully. The Macedo analysis suggests that a tonne of cane used as ethanol fuel represents net avoided emissions equivalent to 220.5 kilograms of carbon dioxide when compared with petroleum with the same energy content. The team extrapolates that ethanol use in Brazil reduces greenhouse-gas emissions by the equivalent of 25.8 million tonnes of carbon dioxide equivalent a year. For comparison, Brazil's total carbon dioxide emissions from fossil fuels is 92 million tonnes a year, according to the US Department of Energy.

The improvement is thus substantial, if not out-of-this-world.

But there are environmental worries that go along with the ethanol industry too: as well as fertilizer and fuel use, there are also pesticides and pollutants such as liquid waste and smoke from burning fields to take into account. Last year, a paper by a group at Washington State University in Richland made headlines by claiming that in this broadest perspective, Brazil's ethanol was bad for the environment2.

This result, though, is disputed — and the industry seems to be getting greener as it goes hunting for efficiency gains. As Christopher Flavin, an analyst at the World Watch Institute, a green pressure group in Washington DC, points out, expansion will generally mean that a higher percentage of the industry

64

will be using newer, cleaner technology (although by the same token it will also be offering fewer unskilled distillery jobs). The leftovers from distillation, once commonly thrown into rivers, are now often spread on fields as potassium fertilizer. Field burning, which by scorching the cane makes it easier to harvest with machetes, is decreasing both as a result of legislation and the increased use of mechanized harvesters. "Thirty-five per cent of cane harvesting is already mechanized," says Nastari, "and it will increase," although because the machines work only on very flat land some burning is likely to continue. Research on planting methods that involve less or no tilling should lead to reduced erosion, too.

Perhaps the biggest environmental worry is that expanding ethanol production will lay waste to natural forests in its path, reducing biodiversity and releasing stored up carbon. The first thing to remember on this front, say the Brazilians, is that Brazil is big. It is big enough to expand its sugar-cane fields massively without either displacing necessary food crops or getting anywhere near the rainforest that the rest of the world seems to have decided is international property. São Paulo state itself is as big as the United Kingdom. Although Brazil is already by far the largest producer of sugar cane in the world, sugar cane is only its fourth biggest commodity, in terms of revenue, with cattle, chicken and soya all bringing in more money. The limiting factor in expansion is capital rather than land."

Growth area

LUIZ CLAUDIO MARIGO/NATUREPL.COM

Interior designs: some of Brazil's Cerrado region could be cleared for sugar-cane plantations.

According to Nastari, cane fields account for just 5.7 million hectares in a country of 850

million hectares. There are already 100 million hectares of old agricultural land or pasture land in the centre-south available for the industry to expand into. Eduardo Pereira de Carvalho, president of Unica, the union of cane-growers in São Paulo, welcomes such expansion with open arms: "As for conflict between food and energy, the fantastic increase in productivity has

65

made all these Malthusian arguments completely nonsense, and we have hundreds of millions of hectares of idle land.

Expansion into at least some of those millions of hectares would probably be more or less carbon-neutral, says Robert Boddey, a soil chemist at Embrapa, the Brazilian agricultural research unit. "For degraded pastures, which are slowly losing carbon, it is not such a bad change. And almost 70% of the Cerrado [Latin America's savanna, of which Brazil has some 200 million hectares] has already been cleared." Because it needs a dry season, sugar cane would not be a good crop to move into cleared rainforest areas, even if that was what anyone wanted. In this respect, cane is more environmentally friendly than palm oil, the most energy-intensive source of biodiesel. Palm-oil plantations for biofuel are having serious effects on the primary forests of Indonesia, but are not as yet big business in Brazil.

R. HODGKINS

Overall, the environmental problems with cane production, says Flavin, are "dwarfed by the land use issues posed by soyabeans and cattle". But they may get worse — or exacerbate the problems elsewhere in agribusiness. Jason Clay of environmental group the WWF points out that "the push of sugar cane is going to displace other crops, and some of them can be grown in the Amazon — cotton, soya, livestock". Some of that soya could be for biodiesel use.

Alex Farrell, head of the Energy and Resources Group at the University of California, Berkeley, adds that for all the enthusiasm there is still a

dearth of evidence on the long-term sustainability or otherwise of cane farming. But, he adds, that is pretty much par for the agricultural course: "All around the world, every government has agriculture — they never ask 'is this agriculture sustainable?' Not for sugarcane, not for rutabagas."

To replace a tenth of today's global petrol production, Brazil's ethanol production would have to grow by a factor of 40 or so. Few see that as likely

66

in itself. Even Unica's de Carvalho, who is undeniably bullish, sees only a doubling by 2014, though he does not see that as the end of the story. Enthusiasts for new cane varieties talk of doubling the yield per hectare, but not necessarily going much further.

But a doubling or two is not to be sniffed at, and there is increasing interest in spreading the techniques developed in this most cane-friendly of countries to others in Latin America and elsewhere, with the details changed to fit local conditions. Already, ethanol is becoming a large enough business for the price of sugar on world markets to respond to changes in the oil markets — so the price of your caipirinha is now, in a very small way, susceptible to the manoeuvres of OPEC.

Nature 444, 670-672 (7 December 2006)

US biofuels: A field in ferment

Katharine Sanderson1

Abstract

To move US biofuels beyond subsidized corn will be a challenge, reports Katharine Sanderson.

Critics of the US ethanol industry have long derided it as an environmentally questionable subsidy to Mid-western farmers that simply serves a transparently political purpose. Voters in Iowa, the buckle in the US corn belt, get first say in the process of choosing presidential candidates. All such candidates are in favour of turning corn (maize), which the state produces in abundance, into ethanol. This pre-presidential support is good for the Iowan economy, but not necessarily that great for the environment.

67

IOGEN

Plant processing: Iogen's enzyme fermentor, a later stage of turning cellulosic feedstock into ethanol.

Studies that compare the energy that goes into making ethanol — expended during the

harvesting, fertilizing and transporting of the corn to refineries, and then refining it — with the energy that is released when it is burned routinely show that the net gain is at best small. The American Coalition for Ethanol says that ethanol contains twice the amount of energy that is used to make it; critics see no net gain whatsoever.

This criticism has had little effect, and since 1980, US ethanol production has risen from an average of 6,500 barrels (1 million litres) a day to 260,000 barrels a day. Federal mandates call for a further doubling by 2012. But it is increasingly clear to many in the industry that the criticisms of corn-based ethanol have merit, and in 2006, the need for an alternative was given the highest profile it could get when President George W. Bush brought it up in his state of the union address. In order to improve US energy security, he said, his government intended to make cellulosic ethanol (ethanol made from the rougher and woodier parts of plants) a competitive biofuel within six years.

Corn stores

The advantage of an ear of corn as a source of ethanol (or for that matter as a bit of food) is that it is mainly starch, which is made up of sugars linked in a regular way with bonds that can be broken easily. Breaking the bonds between sugars and using yeast in the fermentation to produce ethanol is a straightforward task for the biorefineries. The disadvantage is that corn is a crop that needs a lot of inputs — fertilizers, water and pesticides — and that doesn't put as much of the sugar it creates through photosynthesis into its ears as one might wish. A lot of the sugar is instead turned into stalks and 'stover' — structural material rich in cellulose and considerably more difficult to break down.

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Plants that store up a significant amount of energy in easily usable forms such as starch or sugar are exceptions, encouraged in their oddities by millennia of selective breeding — and of them all, only sugar cane grown in the tropics puts enough energy into its easily purified products to make bioethanol obviously attractive (see page 670). Most plants put the bulk of the energy they store up from the sun into cellulose and a related polymer, hemicellulose, and woody plants add another substance, lignin, to the mix. Cellulose makes up the plant's cell walls and, like starch, it is a polymer of sugars containing six carbon atoms linked one to the next. Hemicellulose, on the other hand, is based on a five-carbon sugar, xylose, although it contains many other sugars as well; its various components are thrown together in messy looking chains with many branches. Lignins are huge crosslinked jumbles of organic molecules which reinforce cellulose and hemicellulose to turn them into wood.

The energy that the plants put in to making the bonds in these various substances could, in principle, be extracted by fuel makers. And these molecules — particularly cellulose, which is both the most abundant and the easiest to dismantle — are much more plentiful than starches and sugars. But they are also much harder for microbes to break down; if they weren't, there'd be no trees, just pools of green goo. As yet, there are no cellulosic ethanol refineries operating at full commercial capacity, and assessments of the technology's readiness for market vary a great deal, as do opinions on how to get there from here. Government incentives and tax breaks might be one solution, but big energy companies also have a role to play, as do the smaller companies that have already worked on developing the technology, but have not yet found the best ways of spreading and licensing it.

The most expensive part of making ethanol from cellulose is pretreating the biomass to make it accessible to the enzymes that will then cut the sugars from the polymers so that they can be fermented. Typical pretreatments reduce the feedstock's volume chemically using acids, peroxides and ammonia, often along with some form of mechanical pressing or shredding. Unfortunately, this is not a step that can be skipped to cut costs, says Charles Wyman of the University of California, Riverside, because high sugar yields are essential, and untreated biomass gives very low yields. "The only step more expensive than pretreatment is no pretreatment," he says. Instead, the hunt is on for pre-treatment technologies that involve fewer

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chemicals, require less energy and don't degrade the sugars that are set free in the process.

After the pre-treatment stage comes the snipping out of the sugars, which is the point at which biotechnologists think they can greatly improve on the current process. Abengoa Bioenergy of St Louis, Missouri, a subsidiary of the Spanish engineering group Abengoa, recently invested $10 million in Dyadic International, a biotechnology company that is concentrating on enzymes for degrading cellulose.

Based in Jupiter, Florida, Dyadic didn't start out as an energy company — in the 1970s it was a leading supplier of pumice for stonewashing jeans. But the enzymatic expertise it developed for distressing denim was then turned to a number of other ends. One of those was breaking down wood, a job that in nature largely falls to fungi. The company's research has centred on a filamentous mess of a fungus discovered by accident in a Russian forest that now, after ten years of processing and genetic engineering, makes up Dyadic's patented C1 fungal cell system. The fungus has been fully sequenced and encouraged to overexpress the genes that then make cellulases and xylanases — the proteins that break up cellulose and hemicellulose to produce fermentable sugars. "We have the world's most prolific filamentous fungus," boasts Dyadic's chief executive Mark Emalfarb.

Cellulose solutions

Emalfarb believes that the cellulosic ethanol market could eventually be worth $20 billion a year in the United States, and suggests that there is enough raw material available in the United States to produce 2.4 billion barrels of cellulosic ethanol a year. This is a bit more than half of what some estimates claim is needed to completely replace petrol as a fuel — the United States gets through some 3.3 billion barrels a year, but the energy content of ethanol is lower than that of petroleum.

The current leader in the cellulosic ethanol market, Iogen, also uses fungal enzymes. The company makes small commercial quantities of ethanol from straw at its pioneering cellulosic ethanol facility in Ottawa, Canada. As the first of its kind, this is an undoubted achievement. But even when it reaches its full capacity, which it is taking quite some time to do, it will be capable of

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producing only 2.5 million litres (16,000 barrels) a year, which is not a great deal.

Iogen chief executive Brian Foody is not worried. The critical steps for getting the right enzymes, the right pretreatment systems and the right yeast systems, have all been done, he says. "We just need to go through the nuts and bolts of the process." This means making sure that the demonstration plant works well enough to be replicated elsewhere — the company is looking to build new facilities in Idaho, Saskatchewan and Germany.

Iogen recently secured a $30-million investment from the bankers Goldman Sachs, bringing the total invested in it since the 1970s up to $130 million. But not all potential investors are convinced. "I don't really understand what Iogen is doing," says Matt Drinkwater, market analyst at New Energy Finance in London, UK. And his concerns are not unique to Iogen — many of the companies in the sector, he says, hold details of their processes so close to their chests that they are hard to evaluate, whether they be relatively small outfits such as Iogen or giants such as DuPont, which is also developing cellulosic ethanol technologies. Robert Wilder, who manages the Wilderhill clean energy index — the first such index to be accepted on Wall Street — agrees, but acknowledges the constraints that the chief executives of small cellulosic ethanol companies work under in terms of not tipping their hands to larger competitors.

Smells like green spirit

Perhaps because of these uncertainties over the technology's readiness, most of the money that has been invested recently in ethanol production both within the United States and beyond has been in the more traditional technologies. The sizable investments being made by agribusiness giant Archer Daniels Midland — the biggest ethanol producer in the United States and, perhaps tellingly, a company run by a chief executive who was recruited from the oil industry — seem mostly to be in traditional corn ethanol. The same applies to high-flying UK entrepreneur Richard Branson's recent investments in Ethanol Grain Processors of Tennessee and a new grain-based Californian ethanol venture, Cilion.

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But there is some evidence that enthusiasm for investing in corn ethanol may be waning. Various ethanol companies that were riding high earlier in the year saw their stock slump after the summer when oil prices came down from their $78 a barrel peak.

T. GRAHAM/ALAMY

Pastures new: miscanthus, or elephant grass, is an alternative energy crop grown to produce ethanol.

This might mean the market is aware that, although subsidies may be able to keep it profitable for the time being, there is no way that corn ethanol can

make a marked difference to long-term energy use in the United States. To make enough ethanol to start seriously displacing oil imports requires a process that can use cellulosic materials such as switchgrass, a tall prairie grass, or miscanthus, a grass imported from Asia, which provide far more tonnes of biomass per hectare than corn kernels ever can, and can be grown on land not suitable for conventional agriculture. Other sources could be farm waste or trees or newly engineered plants of some sort (see 'Prairie dreams'). This leads to something of an investing impasse: the companies in the business at the moment make money; the ones that might take it to the next stage do not, in large part because no one has made the heavy capital investments needed for plants that make use of the technologies that have already been piloted.

One way round this is to invest across the board. This is the strategy pursued by Vinod Khosla, the Silicon Valley venture capitalist who is one of the founders of Cilion. Khosla is also involved in cellulosic technologies through two companies based in Cambridge, Massachusetts: Celunol, which has just started to operate its own pilot plant, and Mascoma, which concentrates on process engineering and which last month raised $30 million in second-round venture funding. Farther afield in the biofuels world, Khosla is also a major investor in Kergy, a company that turns biomass into fuel in a completely different 'thermochemical' way, using just heat and

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catalysts. For some observers, such as Dan Schrag, a geochemist at Harvard University, these approaches are more attractive than fermentation, not least because they need no witches' brews made from fiddly feedstock-specific enzyme. "When the dust clears, cellulosic ethanol is unlikely to be where we end up," he predicts (see page 677).

R. HODGKINS

To Drinkwater, investors such as Khosla, with their broad-based approach to the problem, are exactly what the industry needs to drive the market forwards and get it over the final bump it needs to clear before commercial success. Unfortunately, there are few such people. In their absence, many in the industry, not without self-interest, see the responsibility resting with governments to provide attractive tax incentives. "All forms of energy should face market prices that reflect the cost to society that they impose," says Foody. And to set those market prices, the right tax incentives and

government mandates need to be in place.

But government incentives won't make the scientists any smarter, and observers outside the pioneering companies believe there is still basic work to be done before those companies, or their eventual competitors, make the process economically viable. Thus they welcome increasing levels of basic research from the government, such as the US Department of Energy's pledge of $250 million to set up two bioenergy research centres that are largely focused on cellulosic ethanol. The European Union has set aside E100 million (US$132 million) for cellulosic ethanol in its seventh Framework Programme on research.

Ethanol alternative

Companies large enough to afford it are also following the basic research route rather than placing early bets on particular technologies. BP has announced it will invest $500 million over ten years to fund an Energy Biosciences Institute, which will be a dedicated facility based at a university. The University of Cambridge, Imperial College London, Massachusetts

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Institute of Technology, Stanford, the University of California, Berkeley, and Lawrence Berkeley National Laboratory have all been mentioned as possible hosts — the final decision is expected in December.

One intriguing possibility for such research to pursue is replacing ethanol with another form of alcohol. The fact that ethanol is easy to ferment can blind people to the fact that it has almost as many inherent problems as a fuel as corn has as a feedstock. Its tendency to pick up water wherever it goes makes it hard to transport, particularly in pipelines. It's corrosive. It's more volatile than one might wish. And its energy density is low compared with regular petrol.

For these reasons, BP and DuPont are working with British Sugar to adapt their ethanol fermentation facility in East Anglia to produce butanol — an alcohol with four carbons in it, as opposed to ethanol's two. This requires training microbes in new tricks, but it is not as hard a problem as breaking down woody plant material. The East Anglia plant will use locally grown sugar beet as the feedstock, but in the long term the aim would be to use a cellulosic feedstock. "We accept that taking stuff out of the food chain is not the right way to go," says Robert Wine, a BP spokesman.

Drinkwater thinks that an industry demand for butanol as an end product could actually increase interest in cellulosic approaches. "Most refiners would be much happier to use butanol than ethanol," he says. If oil companies become confident in biofuel technologies, investors would in turn be more confident of the biofuels industry as a whole, giving the industry that elusive final shove that it seems to need.

Nature 444, 673-676 (7 December 2006)

Liquid fuel synthesis: Making it up as you go along

Heidi Ledford1

Abstract

Chemists can make liquid fuel from biomass — or from coal. Heidi Ledford weighs up the pros and cons.

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Brian Schweitzer, a rancher and the Democratic governor of Montana, has 'folksy' down to a fine art. In a bolo tie, jeans and cowboy boots, Schweitzer shifts seamlessly from jokes about how his border collie, Jag, drinks out of the toilet to analyses of energy policy in which every complex problem gets its down-to-earth soundbite, from pumping carbon dioxide into the ground ("It came from those rocks, we're just sending it home") to public perceptions of coal as a dirty source of energy ("To a lot of people, coal is a four-letter word").

Put these aperçus all together and you have a pitch for turning coal into oil, an idea Schweitzer and his constituents have 240 billion reasons to take seriously. With 8% of the world's reserves, Montana has enough coal to make 240 billion barrels of diesel fuel, which is in the same ball park as all of the proven reserves claimed by Saudi Arabia.

Schweitzer is far from alone; many politicians and businessmen are now eyeing a chemical process called the Fischer–Tropsch synthesis as a way of converting solid hydrocarbons or natural gas into liquid fuel. The great advantage is energy security: Fischer–Tropsch technology allows domestic coal to replace foreign oil, which is pretty attractive if you're sitting in Washington DC or Beijing, let alone Billings, Butte or Bozeman. Another potential advantage is environmental: the fuel produced by Fischer–Tropsch methods can be made to burn more cleanly than diesel. It could thus ease the adaption of cars with efficient diesel engines in countries, such as the United States, that have so far been resistant to such technology.

The obvious drawback, though, is also environmental. The process of converting coal into liquid and using it for transportation releases nearly twice as much carbon dioxide as burning diesel made from crude oil does. In a world conscious of climate change, that excess carbon is a problem. "If you make liquids from coal and don't capture carbon dioxide in the process, you're effectively doubling emissions," says Eric Larson, a research engineer at Princeton University's Environmental Institute in New Jersey.

One way round this problem might be to take the carbon dioxide and bury it underground. Another would be to replace fossil-fuel feedstock with biomass. That is in some ways an attractive option — but it is also, as yet, an immature technology.

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W. CAMPBELL/CORBIS

Around the bend: is there a feasible future for liquid fuels made from coal?

Expense is another issue. To date, Fischer–Tropsch has always been rather costly, and thus something people normally start to do only when they have no alternatives. Its first major use was during the Second World War, when the blockaded Nazis produced about 90% of their diesel and aviation fuel with the technologies originally developed by Franz Fischer and Hans Tropsch at the Kaiser Wilhelm Institute for Coal

Research in 1923. South Africa began liquefying coal in response to apartheid-era sanctions, and in part as a result of its investment back then, continues to derive about 30% of its fuel from liquefied coal.

To make liquid fuel from coal, you first shatter the long hydrocarbon chains into a mixture of hydrogen and carbon monoxide using high temperatures and intense pressure. This is also the first step for the "integrated gasification combined cycle" plants, seen by many as the future of coal-fired generation — a technology that has many synergies with coal-to-liquids. In Fischer-Tropsch synthesis, the gas is not burned but channelled to a reactor where catalysts reunite the carbon and hydrogen to form hydrocarbon chains of varying lengths, including diesel and petrol. During both phases — gasification and liquefaction — some carbon is given off as carbon dioxide.

Because contaminants such as mercury and sulphur can inhibit the reaction, companies have a built-in incentive to remove impurities from the gas before liquefying it. And the choice of catalyst allows the make-up of synthetic fuel to be tailored to an extent. As a result, diesel produced by the Fischer–Tropsch process is quality stuff. It contains less sulphur and fewer contaminating aromatic compounds, such as benzene and toluene, and releases fewer particulates when burnt than regular diesel fuel does.

Capturing carbon

But none of that solves the carbon dioxide problem. In the United States, all coal-to-liquid plants on the drawing board would include carbon capture

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followed by, in most cases, sequestration, says Lowell Miller, director of the US Department of Energy Office of Sequestration, Hydrogen, and Clean Coal Fuels. That includes the 22,000-barrel-a-day operation near the town of Roundup that Schweitzer has proposed. But the Natural Resources Defense Council (NRDC), a US-based environmental group, says that even if 90% of that carbon were captured, producing and using coal-derived fuels would still release 8% more carbon dioxide than petroleum-derived fuels1. "Even if you do carbon sequestration, at best coal-to-liquid methods are still no better than crude oil in terms of lifecycle emissions," says David Hawkins, director of the NRDC's Climate Center. "And if we are building a new industry to make transportation fuels, we need to build an industry that produces fuels that are significantly lower in carbon dioxide emissions."

In China — which, like the United States, is not bound by the Kyoto Protocol, and which has vast coal reserves — carbon sequestration is less likely. Yong-Wang Li, director of Synfuels China in Shanxi, says that there are two proposed coal-to-liquid industrial plants under consideration in China and that, at present, neither proposal contains plans for sequestering carbon.

The advantage of using plant biomass as a feedstock from which to make synthetic fuel, on the other hand, is that no sequestration is necessary — the emitted carbon is carbon that came from the air in the first place. If one were to add sequestration to a biomass-to-liquids plant, the result could be 'carbon negative', in that the net effect on the atmosphere would be to draw down the level of carbon dioxide as some of the carbon dioxide fixed by the plant would be sequestered into the planet's crust. What's more, Fischer–Tropsch methods could complement, at the very least, some other biomass technologies.

Plant material that contains too much lignin and not enough cellulose for use in cellulosic ethanol

projects (see page 673) could still be used in a Fischer–Tropsch system. The technique could open up the possibility of using forest thinnings and other sources of wood waste, or even the lignin-rich residue left over from cellulosic ethanol production, says David Dayton, a senior scientist at the National Renewable Energy Laboratory in Golden, Colorado. Others think that Fischer–Tropsch could outcompete the fermentation of cellulose more generally.

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But the technology for gasifying biomass currently lags well behind the development of such methods for coal. The Netherlands has invested a lot of research into the process, but still operates only demonstration-scale biomass-only plants. Choren, a German company, and Shell are building a commercial plant in Freiberg, which will produce 15,000 tonnes per year (110,000 barrels per year) of what Choren calls SunDiesel. Construction of five 200,000-tonnes-per-year

facilities that will use wood and agricultural waste is scheduled to begin in 2008. By far the biggest undertaking of its kind to date, the total output from this project would still be enough to supply only about 4% of Germany's projected diesel needs in 2015.

The other big issue is cost. Several US demonstration coal-to-liquid plants, established during the spike in oil prices during the 1970s, closed without leading to further commercial development after oil prices fell in the early 1980s. Miller and Jim Bartis, a policy analyst at the RAND coroporation in Santa Monica, California, both think that oil prices must be above $50–$55 a barrel (159 litres) for coal-to-liquid plants to make long-term economic sense. With oil prices currently just under $60 a barrel that's already an uncomfortably snug fit – and there's no guarantee of prices staying at that level.

Biomass boost

Nevertheless Chevron, Shell and Exxon have all invested in development of Fischer–Tropsch technologies, as has the biggest US coal company, Peabody Coal, which is working on Schweizer's Roundup plant with Rentech of Denver, Colorado. "Some of the big players are willing to take a low rate of return just to establish a technology position," says Bartis. "Once you build a first plant, you're going to learn by doing, and subsequent plants are going to cost less." Another strategy is to concentrate on people who might pay a premium for domestic hydrocarbons. Syntroleum of Tulsa, Oklahoma, recently provided samples of its natural-gas-derived jet fuel, made with technology licensed from Exxon Mobil, to the US Air Force for testing.

R. HODGKINS

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For biomass, the situation is worse. Robin Zwart of the Dutch Energy Research Centre in Petten hopes that upcoming improvements in efficiency will drive the price down, but says that oil prices will still have to exceed $70–80 per barrel to make liquid fuels from, for example, willow trees economical. That said, carbon taxation or emissions trading would give a boost to biomass-based systems that are unavailable to coal-to-liquid systems.

That is why, until biomass supply and technology are scaled up, there is still the appealing option of spiking coal feedstock with biomass. Coupled with carbon sequestration, this would reduce greenhouse gas emissions without requiring much change to existing technology, says Robert Williams, a researcher at Princeton University's Environmental Institute. Williams has calculated that a mixture of 89% coal and 11% biomass could reduce carbon emissions by 19% relative to using the same process with coal only.

Because they can't yet make money, current Fischer–Tropsch projects often involve a complex mix of industry partners and government subsidies. Sasol of South Africa, a veteran in the easier gas-to-liquids game, considers government subsidies crucial. Sasol is conducting feasibility studies for coal-to-liquid projects in China and India, and has partnered with oil giant Chevron in Europe. But it is waiting to see what develops with government subsidies, according to chief executive Pat Davies, before committing to any US projects.

So far, the US federal government has proposed tax credits for coal-to-liquid programmes, and provides grants to interested companies. States are also pitching in: Pennsylvania, for example, is guaranteeing $465 million in loans and $47 million in tax credits for a proposed plant in Schuylkill County. Elsewhere in the world — in China, India and the Philippines, for example — liquefaction projects have received pledges of strong government support. And in Germany, biomass-derived fuels are exempt from the heavy taxes levied on other fuels.

Miller says he is optimistic that Fischer–Tropsch fuels could finally establish a foothold in the United States. But 30 years of studying coal-to-liquid technology has taught him to temper his enthusiasm with caution. "I've been in this business for a long time," he says, "and I'll believe it when the shovel goes into the ground."

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Nature 444, 677-678 (7 December 2006)

《科学》发表的有中国大陆科学家署名的文章（2005 年 23篇、2004 年 15篇）

1. HIV Testing in China Zunyou Wu, Xinhua Sun, Sheena G. Sullivan, and Roger Detels Science 9 June 2006; 312(5779): p. 1475-1476

2. Long-Term Potentiation of Neuron-Glia Synapses Mediated by Ca2+-Permeable AMPA Receptors Woo-Ping Ge, Xiu-Juan Yang, Zhijun Zhang, Hui-Kun Wang, Wanhua Shen, Qiu-Dong Deng, and Shumin Duan Science 9 June 2006; 312(5779): p. 1533-1537

3. Converting Ceria Polyhedral Nanoparticles into Single-Crystal Nanospheres Xiangdong Feng, Dean C. Sayle, Zhong Lin Wang, M. Sharon Paras, Brian Santora, Anthony C. Sutorik, Thi X. T. Sayle, Yi Yang, Yong Ding, Xudong Wang, and Yie-Shein Her Science 9 June 2006; 312(5779): p. 1504-1508

4. Enhanced Mid-Latitude Tropospheric Warming in Satellite Measurements Qiang Fu, Celeste M. Johanson, John M. Wallace, and Thomas Reichler Science 26 May 2006; 312(5777): p. 1179

5. Lower Cambrian Vendobionts from China and Early Diploblast Evolution D.-G. Shu, S. Conway Morris, J. Han, Y. Li, X.-L. Zhang, H. Hua, Z.-F. Zhang, J.-N. Liu, J.-F. Guo, Y. Yao, and K. Yasui Science 5 May 2006; 312(5774): p. 731-734

6. Piezoelectric Nanogenerators Based on Zinc Oxide Nanowire Arrays Zhong Lin Wang and Jinhui Song Science 14 April 2006; 312(5771): p. 242-246

7. Ultrafast Interfacial Proton-Coupled Electron Transfer Bin Li, Jin Zhao, Ken Onda, Kenneth D. Jordan, Jinlong Yang, and Hrvoje Petek Science 10 March 2006; 311(5766): p. 1436-1440

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8. Observation of Feshbach Resonances in the F + H2 -> HF + H Reaction Minghui Qiu, Zefeng Ren, Li Che, Dongxu Dai, Steve A. Harich, Xiuyan Wang, Xueming Yang, Chuanxiu Xu, Daiqian Xie, Magnus Gustafsson, Rex T. Skodje, Zhigang Sun, and Dong H. Zhang Science 10 March 2006; 311(5766): p. 1440-1443

9. Laonastes and the "Lazarus Effect" in Recent Mammals Mary R. Dawson, Laurent Marivaux, Chuan-kui Li, K. Christopher Beard, and Gregoire Metais Science 10 March 2006; 311(5766): p. 1456-1458

10.A Swimming Mammaliaform from the Middle Jurassic and comorphological Diversification of Early Mammals Qiang Ji, Zhe-Xi Luo, Chong-Xi Yuan, and Alan R. Tabrum Science 24 February 2006; 311(5764): p. 1123-1127

11.X-ray Flares from Postmerger Millisecond Pulsars Z. G. Dai, X. Y. Wang, X. F. Wu, and B. Zhang Science 24 February 2006; 311(5764): p. 1127-1129

12.Structure of Human Urokinase Plasminogen Activator in Complex with Its Receptor Qing Huai, Andrew P. Mazar, Alice Kuo, Graham C. Parry, David E. Shaw, Jennifer Callahan, Yongdong Li, Cai Yuan, Chuanbing Bian, Liqing Chen, Bruce Furie, Barbara C. Furie, Douglas B. Cines, and Mingdong Huang Science 3 February 2006; 311(5761): p. 656-659

13.The Distance to the Perseus Spiral Arm in the Milky Way Y. Xu, M. J. Reid, X. W. Zheng, and K. M. Menten Science 6 January 2006; 311(5757): p. 54-57

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