PNAS:废气转化成液态燃料
美国麻省理工学院一项研究发现，一种由细菌和酵母推动的相对廉价的过程可能有助于把来自钢铁厂和其它来源的废气转换成液态燃料。面对温室气体浓度的猛增和不断减少的化石燃料贮藏，科研人员寻求清洁而可再生的能源。尽管近来的研究已经证明了诸如大肠埃希氏菌等经过改造的细菌能把碳水化合物转化成生物柴油的前体，糖原料对于大规模生产过于昂贵。Gregory Stephanopoulos及其同事开发了一个廉价的生物过程，用于把气体转化成液态燃料，它使用热醋穆尔氏菌(Moorella thermoacetica)和经过改造的酵母。这个两阶段过程始于一个生物反应器，在其中，热醋穆尔氏菌把二氧化碳气体和一氧化碳或氢气的混合物——它们常常被称为合成气——转化成乙酸。第二步，这些乙酸被投入到有解脂耶罗维亚酵母(Yarrowia lipolytica)的第二个反应器中，这个酵母物种把这种化合物处理成可以继而转化成生物柴油的液体。这组作者说，这个方法可能有潜力扩展到一批产生包括二氧化碳在内的废气的商业应中。
原文链接：
Integrated bioprocess for conversion of gaseous substrates to lIQuids
原文摘要：
In the quest for inexpensive feedstocks for the cost-effective production of liquid fuels, we have examined gaseous substrates that could be made available at low cost and sufficiently large scale for industrial fuel production. Here we introduce a new bioconversion scheme that effectively converts syngas, GENErated from gasification of coal, natural gas, or biomass, into lipids that can be used for biodiesel production. We present an integrated conversion method comprising a two-stage system. In the first stage, an anaerobic bioreactor converts mixtures of gases of CO2 and CO or H2 to acetic acid, using the anaerobic acetogen Moorella thermoacetica. The acetic acid product is fed as a substrate to a second bioreactor, where it is converted aerobically into lipids by an engineered oleaginous yeast, Yarrowia lipolytica. We first describe the process carried out in each reactor and then present an integrated system that produces microbial oil, using synthesis gas as input. The integrated continuous bench-scale reactor system produced 18 g/L of C16-C18 triacylglycerides directly from synthesis gas, with an overall productivity of 0.19 g⋅L−1⋅h−1 and a lipid content of 36%. Although suboptimal relative to the performance of the individual reactor components, the presented integrated system demonstrates the feasibility of substantial net fixation of carbon dioxide and conversion of gaseous feedstocks to lipids for biodiesel production. The system can be further optimized to approach the performance of its individual units so that it can be used for the economical conversion of waste gases from steel mills to valuable liquid fuels for transportation.
作者：Peng Hu
