SusChEM: Drop-in Hydrocarbon Fuels through Novel Integration of Biological and Catalytic Conversion of Cellulosic Biomass-Derived Sugars

项目名称：Ian wheeldon提案编号：1510697植物生物质是一种丰富的国内资源，可用于可持续和大规模生产液体运输燃料。这种生物质转化为燃料的系统减少了对化石燃料的依赖，减少了温室气体的产生，并改善了能源安全。目前将植物生物质转化为燃料的方法通常涉及生物过程，例如使用微生物将纤维素组分转化为糖，然后发酵成生物乙醇，或化学过程，通常将生物质转化为反应气体，然后升级为各种燃料化合物。该项目的目标是将生物和化学过程的最佳属性结合到一个单一的综合过程中，有选择地将生物质糖转化为类似汽油的液态碳氢化合物燃料。该项目的创新之处在于，它通过乙酸乙酯将这两个过程结合在一起，乙酸乙酯是一种由酵母产生的中间化合物，很容易分离并催化转化为高产量和高纯度的汽油。基础研究将使用基因工程技术，使酵母菌专门制造乙酸乙酯而不是乙醇，然后调整催化剂系统，使其从乙酸乙酯中生产汽油。这项研究将包括来自加州里弗赛德县当地社区大学的代表性不足的本科生。该研究的总体目标是探索整合选择性生物和催化转化过程将植物生物质衍生糖转化为液体燃料的可行性。总体概念是充分利用这两种工艺的独特特点，使生物质糖选择性转化为碳氢化合物。选择用于基础研究的特定系统侧重于酵母的代谢工程，用于乙酸乙酯的生物合成，然后在汽油范围内催化乙酸乙酯转化为碳氢化合物。选择乙酸乙酯作为中间产物，有效地连接生物和化学转化步骤，因为它的高挥发性允许从发酵液中作为蒸汽产物回收，并且对催化转化为碳氢化合物具有反应性。选择K. maximus作为乙酸乙酯生物合成的模式生物，因为它是一种适合基因工程的工业酵母菌株，具有从发酵液中回收乙酸乙酯蒸汽所需的50℃耐热性，并且可以代谢来自木质纤维素生物质的C5和C6糖。研究计划有两个主要目标。第一个目标是确定马氏克卢维菌醋酸乙酯的生物合成途径，并利用这些知识通过代谢工程最大化乙酸乙酯的生产。为此，假设乙酸乙酯是通过三种途径之一合成的，包括酒精-乙酰基转移酶（AATase）、反酯酶活性或酒精脱氢酶（Adh）对半缩醛的合成。途径将针对C5和C6糖进行优化。第二个目标是开发和表征一种新的催化反应途径，将乙酸乙酯蒸汽转化为汽油碳氢化合物，使用纳米颗粒贵金属/氧化铝氢解催化剂将乙酸乙酯转化为乙醚，使用形状选择性固体酸沸石催化剂将乙醚转化为碳氢化合物。

PI Name: Ian WheeldonProposal Number: 1510697 Plant biomass is an abundant, domestic resource for the sustainable and large-scale production of liquid transportation fuels. Such biomass-to-fuel systems reduce dependence on fossil fuels, lower greenhouse gas production, and improve energy security. Present processes for converting plant biomass into fuels usually involve biological processes, such as using microorganisms to convert the cellulosic fractions to sugars which are fermented into bioethanol, or chemical processes, which typically convert the biomass to a reactive gas which is then upgraded to a wide range of fuel compounds. The goal of this project is combine the best attributes of biological and chemical processes into a single integrated process that selectively converts biomass sugars into liquid hydrocarbon fuels similar to gasoline. The innovative aspect of this project is that it ties both processes together through ethyl acetate, an intermediate compound produced by yeast which is readily separated and catalytically converted to gasoline with high yield and purity. The fundamental research will use genetic engineering to enable the yeast to exclusively make ethyl acetate instead of ethanol, and then tailor the catalyst systems to make gasoline from ethyl acetate. The research will include undergraduate student participants from under-represented backgrounds attending local community colleges in Riverside County, California.The overall goal of the proposed research is to explore the feasibility of integrating selective biological and catalytic conversion processes to convert plant biomass derived sugars into liquid fuels. The overall concept is to take best advantage of the unique features of both processes to enable selective conversion of biomass sugars to hydrocarbons. The particular system chosen for fundamental study focuses on the metabolic engineering of the yeast Kluyveromyces marxianus for ethyl acetate biosynthesis, followed by the catalytic conversion of ethyl acetate to hydrocarbons in the gasoline range. Ethyl acetate is selected as the intermediate product to efficiently link the biological and chemical conversion steps, since its high volatility allows for recovery as vapor product from the fermentation broth, and is reactive towards catalytic conversion to hydrocarbons. K. maxiumus is selected as the model organism for ethyl acetate biosynthesis, as it is an industrial yeast strain amenable to genetic engineering, exhibits thermal tolerance at 50 C needed for ethyl acetate vapor recovery from the fermentation broth, and can metabolize both C5 and C6 sugars derived from lignocellulosic biomass. The research plan has two primary objectives. The first objective is to identify ethyl acetate biosynthesis pathways in Kluyveromyces marxianus, and use this knowledge to maximize ethyl acetate production through metabolic engineering. Towards this end, it is hypothesized that ethyl acetate is synthesized by one of three pathways, including synthesis by alcohol-Oacetyltransferase (AATase), reverse esterase activity, or alcohol dehydrogenase (Adh) activity towards hemiacetal. Pathways will be optimized for both C5 and C6 sugars. The second objective is to develop and characterize a new catalytic reaction pathway for conversion of ethyl acetate vapor to gasoline hydrocarbons, using nanoparticle based noble metal/alumina hydrogenolysis catalysts to convert ethyl acetate to diethyl ether, and shape-selective, solid-acid zeolite catalysts to convert diethyl ether to hydrocarbons.