UNS: Collaborative Research: Biodiesel-derived butanol: Lipid vesicle mediated extraction enables continuous fermentation processes

项目编号：1508844 / 1509244丁醇是一种很有前途的高级生物燃料，因为它具有接近汽油的高能量含量，可以作为替代燃料。然而，丁醇比乙醇更难通过发酵生产。这是因为丁醇产品对发酵过程有毒，导致低浓度的丁醇成本太高，无法经济地回收。该项目将开发一种新的发酵工艺，使用无毒溶剂在生产丁醇时去除丁醇，从而降低毒性并提高丁醇总产量。此外，所选择的微生物，巴氏梭菌，发酵生产丁醇的粗甘油，生物柴油生产的副产物。通过这项调查，本科生和研究生将接受可再生燃料技术方面的培训，并将接受沟通技巧和公共宣传方面的专门培训。通过发酵生产丁醇通常会由于多种因素导致丁醇产量低，包括微生物对丁醇的耐受性低，难以将代谢途径转向丁醇生物合成，以及传统提取发酵技术的局限性。最近，正在进行的研究表明，利用粗甘油作为唯一底物，巴氏梭菌可以获得高丁醇产量。粗甘油是脂肪酸原料生产生物柴油的副产物。本研究的总体目标是通过了解在以粗甘油为底物的连续发酵过程中生物相容性脂质囊泡对丁醇的提取去除与丁醇耐受性之间的关系，提高巴氏杆菌的丁醇产量。连续培养将用于确定膜脂组成的变化和维持能量响应丁醇和底物的添加。这种方法将用于将耐受性、毒性和底物利用与丁醇生产联系起来。连续培养与脂质囊泡萃取发酵相结合，有可能通过两种工艺提高丁醇产量。首先，将研究囊泡介导提取粗甘油，以去除生物柴油衍生甘油中残留的脂肪酸，这些脂肪酸已知会抑制甘油发酵成丁醇。其次，将研究生物相容性脂质囊泡原位提取发酵通过质量作用效应刺激与丁醇生物合成相关的代谢途径的潜力。该项目还为教育学生、教师和社区有关生物燃料可持续生产的知识提供了机会，并通过罗德岛大学的梅特卡夫研究所培养学生在这方面的沟通技巧。将创建跨学科模块，来自罗德岛大学和亨茨维尔阿拉巴马大学的学生将共同研究与生物炼制操作相关的生物分离过程。

PI: Geoffrey D. Bothun / Carmen ScholzProposal Number: 1508844 / 1509244Butanol is a promising advanced biofuel because it has a high energy content approaching that of gasoline, and can serve as a drop-in replacement fuel. However, butanol is more difficult to produce by fermentation relative to ethanol. This is because the butanol product is toxic to the fermentation process, resulting in low concentrations of butanol that are too costly to recover economically. This project will develop a novel fermentation process that uses a nontoxic solvent to remove butanol while it is being produced, which reduces toxicity and increases overall butanol yield. Furthermore, the microorganism chosen for study, Clostridium pasteurianum, makes butanol from fermentation of crude glycerol, the by-product of biodiesel manufacture. Through this investigation, undergraduate and graduate students will be trained in renewable fuel technologies, and will receive specialized training in communication skills and public outreach.The production of butanol by fermentation typically results in low butanol yields due a variety of factors, including low butanol tolerance of microorganisms, difficulty in redirecting the metabolic pathway towards butanol biosynthesis, and limitations of conventional extractive fermentation techniques. Recently, ongoing research has shown that the bacterium Clostridium pasteurianum can achieve high butanol yields using crude glycerol as the sole substrate. Crude glycerol is the byproduct of biodiesel production from fatty acid feedstocks. The overall goal of this research is to enhance butanol production by C. pasteurianum through understanding of the relationships between butanol tolerance and its extractive removal by biocompatible lipid vesicles during continuous fermentation on crude glycerol as the substrate. Continuous cultures will be used to determine changes in membrane lipid composition and maintenance energy in response to butanol and substrate addition. This approach will used to connect tolerance, toxicity, and substrate utilization to butanol production. Continuous culture combined with lipid vesicle-based extractive fermentation has the potential to enhance the butanol yield through two processes. First, vesicle-mediated extraction of the crude glycerol will be studied to remove residual fatty acids in the biodiesel-derived glycerol, which are known to inhibit glycerol fermentation to butanol. Second, in situ extractive fermentation with the biocompatible lipid vesicles will be studied for its potential to stimulate the metabolic pathway associated with butanol biosynthesis through the mass-action effect. The project also provides opportunities to educate students, teachers, and communities about the sustainable production of biofuels, and to develop the communication skills of students in this context through Metcalf Institute at the University of Rhode Island. Interdisciplinary modules will be created where students from the University of Rhode Island and the University of Alabama in Huntsville will work together on bioseparation processes relevant to biorefinery operations.