生物质燃料

石化资源的溃乏以及其飚升的价格使得今天生物能源的研究越来越受到关注。从传统的生物供能方式——燃烧开始,介绍发酵制气、生物电池等最新的生物供能方式,以求对生物燃料作一较为详细的介绍,并对其应用前景进行展望。     

Life cycle assessment of native plants and marginal lands for bioenergy agriculture in Kentucky as a model for south-eastern USA

The Brookings Institute analysis rate both Lexington and Louisville, Kentucky (USA) as two of the nation's largest carbon emitters. This high carbon footprint is largely due to the fact that 95% of electricity is produced from coal. Kentucky has limited options for electric power production from low carbon sources such as solar, wind, geothermal, and hydroelectric. Other states (TN, IN, OH, WV, and IL) in this region are similarly limited in renewable energy capacity. Bioenergy agriculture could account for a proportion of renewable energy needs, but to what extent is unclear. Herein, we found that abandoned agricultural land, not including land that is in fallow or crop rotation, aquatic ecosystems, nor plant-life that had passed through secondary ecological succession totaled 1.9 Mha and abandoned mine-land totaled 0.3 Mha, which combined accounted for 21% of Kentucky's land mass. A life cycle assessment was performed based on local yield and agronomic data for native grass bioenergy agriculture. These data showed that utilizing Kentucky's marginal land to grow native C ₄ grasses for cellulosic ethanol and bioelectricity may account for up to 13.3% and 17.2% of the states 2 trillion MJ energy consumption and reduce green house gas emissions by 68% relative to gasoline.     

纤维燃料丁醇研究进展

随着能源危机与粮食安全问题的日趋加重,以纤维质为原料生产石油替代燃料已成为生物质能研究的重点。分析了丁醇作为燃料的优点,归纳了丁醇发酵微生物的种类与研究现状,综述了纤维原料生产燃料丁醇的研究进展,最后对我国纤维燃料丁醇的产业化优势和前景进行了分析与展望。     

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Microalgae have been shown as a potential bioresource for food, biofuel, and pharmaceutical products. During the growth phases with corresponding environmental conditions, microalgae accumulate different amounts of various metabolites. We quantified the neutral lipids accumulation and analyzed the swimming signatures (speed and trajectories) of the motile green alga, Dunaliella primolecta, during the lag–exponential–stationary growth cycle at different nutrient concentrations. We discovered significant changes in the neutral lipid content and swimming signatures of microalgae across growth phases. The timing of the maximum swimming speed coincided with the maximum neutral lipid content and both maxima occurred under nutrient stress at the stationary growth phase. Furthermore, the swimming trajectories suggested statistically significant changes in swimming modes at the stationary growth phase when the maximum intracellular neutral lipid content was observed. Our results provide the potential exploitation of microalgal swimming signatures as possible indicators of the cultivation conditions and the timing of microalgal harvest to maximize the lipid yield for biofuel production. The findings can also be implemented to explore the production of food and antibiotics from other microalgal metabolites with low energy costs.     

能源植物资源的研究和开发

植物能源是一种清洁的、方便的可替代能源,发展植物能源是解决矿石能源危机的可行的措施,生物汽油和生物柴油产业已得到初步发展和应用。按照能源植物所含特定化学物质的对能源植物进行类别划分,并结合我国的实际,提出我国适宜发展的能源植物品种。     

Plant biotechnology for lignocellulosic biofuel production

Lignocelluloses from plant cell walls are attractive resources for sustainable biofuel production. However, conversion of lignocellulose to biofuel is more expensive than other current technologies, due to the costs of chemical pretreatment and enzyme hydrolysis for cell wall deconstruction. Recalcitrance of cell walls to deconstruction has been reduced in many plant species by modifying plant cell walls through biotechnology. These results have been achieved by reducing lignin content and altering its composition and structure. Reduction of recalcitrance has also been achieved by manipulating hemicellulose biosynthesis and by overexpression of bacterial enzymes in plants to disrupt linkages in the lignin–carbohydrate complexes. These modified plants often have improved saccharification yield and higher ethanol production. Cell wall‐degrading (CWD) enzymes from bacteria and fungi have been expressed at high levels in plants to increase the efficiency of saccharification compared with exogenous addition of cellulolytic enzymes. In planta expression of heat‐stable CWD enzymes from bacterial thermophiles has made autohydrolysis possible. Transgenic plants can be engineered to reduce recalcitrance without any yield penalty, indicating that successful cell wall modification can be achieved without impacting cell wall integrity or plant development. A more complete understanding of cell wall formation and structure should greatly improve lignocellulosic feedstocks and reduce the cost of biofuel production.     

Isolation and characterization of lignin‐degrading bacteria from rainforest soils

The deconstruction of lignin to enhance the release of fermentable sugars from plant cell walls presents a challenge for biofuels production from lignocellulosic biomass. The discovery of novel lignin‐degrading enzymes from bacteria could provide advantages over fungal enzymes in terms of their production and relative ease of protein engineering. In this study, 140 bacterial strains isolated from soils of a biodiversity‐rich rainforest in Peru were screened based on their oxidative activity on ABTS, a laccase substrate. Strain C6 (Bacillus pumilus) and strain B7 (Bacillus atrophaeus) were selected for their high laccase activity and identified by 16S rDNA analysis. Strains B7 and C6 degraded fragments of Kraft lignin and the lignin model dimer guaiacylglycerol‐β‐guaiacyl ether, the most abundant linkage in lignin. Finally, LC–MS analysis of incubations of strains B7 and C6 with poplar biomass in rich and minimal media revealed that a higher number of compounds were released in the minimal medium than in the rich one. These findings provide important evidence that bacterial enzymes can degrade and/or modify lignin and contribute to the release of fermentable sugars from lignocellulose. Biotechnol. Bioeng. 2013; 110: 1616–1626. © 2013 Wiley Periodicals, Inc.     

生物丁醇制造技术现状和展望

丁醇是大宗基础化工原料,并有望成为新一代生物燃料。利用可再生原料通过微生物发酵生产丁醇受到人们的很大关注。然而,与石油原料制造丁醇相比,目前生物丁醇的制造成本偏高。生物丁醇制造技术按重要性排序:在廉价原料替代、低丁醇浓度及存在丙酮、乙醇低值副产物3个方面有改进空间。上海生物丁醇协作组设定了由易到难的技术路线图:通过代谢工程提高丁醇比例;在丁醇高耐受菌株中导入和优化丁醇合成途径;去除葡萄糖阻遏效应使之可利用复杂原料。协作组相信,通过与国内外广泛的产学研合作,应可在不远的将来开发出有经济竞争力并可持续发展的生物丁醇生产工艺。     

生物燃料最新发展态势分析

第一代生物燃料的生产工艺已经较为成熟,美国、欧盟和巴西等一些国家已经形成了较完善的产业链。以纤维素乙醇为代表的第二代生物燃料是更有希望的替代燃料,但目前还未获得关键性的技术突破,其大规模的商业化生产还有待时日。目前生物燃料正处于由第一代向第二代发展过渡的初期。各国纷纷将发展第二代生物燃料定为国策,为此制订了长期的发展规划与目标,并为生物燃料发展提供了良好的政策环境和大力的经费支持。各相关研究机构与企业也积极行动,力图解决生物燃料发展的各个关键问题。在此过程中,一些与生物燃料可持续发展有关的重要问题也引起了人们的关注。     

Biofuel anode based on d-glucose dehydrogenase,nicotinamide adenine dinucleotide and a modified electrode

A biofuel cell anode has been made from a modified graphite electrode and immobilized d-glucose dehydrogenase [β-d-glucose:NAD(P)⁺ 1-oxidoreductase, EC 1.1.1.4 7] so that energy could be drawn from the conversion of d-glucose to d-gluconic acid. An equivalent amount of dihydronicotinamide adenine dinucleotide (NADH) was formed from NAD⁺ and reduced the surface groups of the modified electrode. Reoxidationn of the latter produced the electrons necessary for a power output from the cell. Electrode modification was made by adsorption of N,N-dimethyl-7-amino 1,2-benzophenoxazinium onto the graphite. A current density of 0.2 mA cm^?2 at a cell voltage of ～0.8 V was obtained for more than 8 h with a simulated oxygen cathode. The internal resistance in the cell, in particular in the separator, appeared to be the main current-limiting factor.     

面向先进生物燃料的合成生物学

先进生物燃料一般指来自于非粮食原料的交通运输用生物燃料。近年来,先进生物燃料的发展引起了众多国家的浓厚兴趣,然而,先进生物燃料正处于关键的技术研发阶段,还需经过大量研发以突破技术障碍和示范生产活动后方能进行商业化部署。过去10年内,合成生物学研究大量兴起并不断取得突破,使人们有可能人工设计构建新的高效生命系统,克服生物燃料发展的技术瓶颈,进行先进生物燃料的生产。在介绍先进生物燃料与合成生物学的发展现状的基础上,分析了合成生物学在先进生物燃料研发中的重要价值与研发进展,探讨了合成生物学的发展潜力。     

Is biofuel policy harming biodiversity in Europe?

We assessed the potential impacts of land-use changes resulting from a change in the current biofuel policy on biodiversity in Europe. We evaluated the possible impact of both arable and woody biofuel crops on changes in distribution of 313 species pertaining to different taxonomic groups. Using species-specific information on habitat suitability as well as land use simulations for three different biofuel policy options, we downscaled available species distribution data from the original resolution of 50 to 1 km. The downscaled maps were then applied to analyse potential changes in habitat size and species composition at different spatial levels. Our results indicate that more species might suffer from habitat losses rather than benefit from a doubled biofuel target, while abolishing the biofuel target would mainly have positive effects. However, the possible impacts vary spatially and depend on the biofuel crop choice, with woody crops being less detrimental than arable crops. Our results give an indication for policy and decision makers of what might happen to biodiversity under a changed biofuel policy in the European Union. The presented approach is considered to be innovative as to date no comparable policy impact assessment has been applied to such a large set of key species at the European scale.     

Climate change, biofuels and eco-social impacts in the Brazilian Amazon and Cerrado

While global technical progress is relatively linear, there is wide variation in its environmental and social impacts at the local level, with cycles of expansion and retraction or boom and bust, of long or short duration. Analysis of previous open-ended stages of extraction and agro commodities in the Amazon indicates a general gravitational trend for technical progress to increase productivity and permit transformation of increasingly generic forms of material or energy, rather than relying on the specific physical or chemical properties provided by nature. While increased demand favours frontier expansion in the periphery when there is no other alternative, technical progress ultimately favours spatial reconcentration of production in central countries. The agroenergy stage now beginning involves rapid frontier expansion and offers various environmental and economic opportunities, but also generates a series of negative ecosystemic and socio-economic impacts, which are both direct and indirect, for tropical regions. The Amazon and the Cerrado are particularly vulnerable. Interacting with climate change and land use, the upcoming stage of cellulosic energy could result in a collapse of the new frontier into vast degraded pasture. The present and future impacts can be mitigated through crafting of appropriate policies, not limited to the Amazon, stressing intensified and more sustainable use of areas already cleared, minimizing new clearing and consolidation of alternatives for sustainable use of natural resources by local communities. Coping with these scenarios requires knowledge of complex causal relationships.     

巴西生物燃料政策及对我国的启示

巴西是世界上最早推行生物燃料政策的国家之一,目前已成为世界上第二大乙醇生产国和最大的乙醇出口国。本文简介了巴西推行生物燃料政策的背景、发展生物燃料的优势,详述了其生物燃料的政策特点和政策收益,以及对我国发展生物燃料的启示。     

宏基因组技术在新型生物燃料生产酶制剂开发中的应用

随着石化燃料的日益减少,以植物生物质为原料的可再生生物燃料成为石化燃料的理想替代品。然而微生物降解生物质效率低下,是生物燃料生产过程中一大难题,因此开发效率高、稳定性强的微生物酶制剂显得尤为重要。近年来,宏基因组技术的发展为生物燃料的生产提供了多种新型酶制剂。宏基因组技术是直接提取环境样品中的总DNA,通过构建文库,筛选目的基因或功能基因的方法,在用于燃料生产的新型酶制剂的开发中发挥着重要作用。本文概述了宏基因组技术的实施策略,总结了包括纤维素酶、蛋白酶、酯酶、脂肪酶等多种酶资源开发的最新研究进展,并综合和讨论了通过酶法将木质纤维素等生物材料有效转化为生物燃料的途径,为新酶的开发提供了新思路。     

Microalgae–bacteria symbiosis in microalgal growth and biofuel production: a review

Photosynthetic microalgae can capture solar energy and convert it to bioenergy and biochemical products. In nature or industrial processes, microalgae live together with bacterial communities and may maintain symbiotic relationships. In general interactions, microalgae exude dissolved organic carbon that becomes available to bacteria. In return, the bacteria remineralize sulphur, nitrogen and phosphorous to support the further growth of microalgae. In specific interactions, heterotrophic bacteria supply B vitamins as organic cofactors or produce siderophores to bind iron, which could be utilized by microalgae, while the algae supply fixed carbon to the bacteria in return. In this review, we focus on mutualistic relationship between microalgae and bacteria, summarizing recent studies on the mechanisms involved in microalgae–bacteria symbiosis. Symbiotic bacteria on promoting microalgal growth are described and the relevance of microalgae–bacteria interactions for biofuel production processes is discussed. Symbiotic microalgae–bacteria consortia could be utilized to improve microalgal biomass production and to enrich the biomass with valuable chemical and energy compounds. The suitable control of such biological interactions between microalgae and bacteria will help to improve the microalgae-based biomass and biofuel production in the future.     

The effect of rapamycin on biodiesel-producing protist Euglena gracilis

Rapamycin induces autophagy with lipid remodeling in yeast and mammalian cells. To investigate the lipid biosynthesis of Euglena gracilis, rapamycin was supplemented in comparison with two model algae, Chlamydomonas reinhardtii and Cyanidioschyzon merolae. In Euglena, rapamycin induced the reduction of chlorophylls and the accumulation of neutral lipids without deterring its cell proliferation. Its lipidomic profile revealed that the fatty acid composition did not alter by supplementing rapamycin. In Chlamydomonas, however, rapamycin induced serious growth inhibition as reported elsewhere. With a lower concentration of rapamycin, the alga accumulated neutral lipids without reducing chlorophylls. In Cyanidioschyzon, rapamycin did not increase neutral lipids but reduced its chlorophyll content. We also tested fatty acid elongase inhibitors such as pyroxasulfone or flufenacet in Euglena with no significant change in its neutral lipid contents. In summary, controlled supplementation of rapamycin can increase the yield of neutral lipids while the scheme is not always applicable for other algal species.     

Simultaneous saccharification and fermentation of amorphous cellulose to ethanol by recombinant Klebsiella oxytoca SZ21 without supplemental cellulase

A derivative of Klebsiella oxytoca M5A1 containing chromosomally integrated genes for ethanol production from Zymomonas mobilis (pdc, adhB) and endoglucanase genes from Erwinia chrysanthemi (celY, celZ) produced over 20 000 U endoglucanase l^–1 activity during fermentation. In combination with the native ability to metabolize cellobiose and cellotriose, this strain was able to ferment amorphous cellulose to ethanol (58–76% of theoretical yield) without the addition of cellulase enzymes from other organisms.     

Cell-wall carbohydrates and their modification as a resource for biofuels

Plant cell walls represent the most abundant renewable resource on this planet. Despite their great abundance, only 2% of this resource is currently used by humans. Hence, research into the feasibility of using plant cell walls in the production of cost-effective biofuels is desirable. The main bottleneck for using wall materials is the recalcitrance of walls to efficient degradation into fermentable sugars. Manipulation of the wall polysaccharide biosynthetic machinery or addition of wall structure-altering agents should make it possible to tailor wall composition and architecture to enhance sugar yields upon wall digestion for biofuel fermentation. Study of the biosynthetic machinery and its regulation is still in its infancy and represents a major scientific and technical research challenge. Of course, any change in wall structure to accommodate cost-efficient biofuel production may have detrimental effects on plant growth and development due to the diverse roles of walls in the life of a plant. However, the diversity and abundance of wall structures present in the plant kingdom gives hope that this challenge can be met.