Problems with the microbial production of butanol.
With the incessant fluctuations in oil prices and increasing stress from environmental pollution, renewed attention is being paid to the microbial production of biofuels from renewable sources. As a gasoline substitute, butanol has advantages over traditional fuel ethanol in terms of energy density and hygroscopicity. A variety of cheap substrates have been successfully applied in the production of biobutanol, highlighting the commercial potential of biobutanol development. In this review, in order to better understand the process of acetone-butanol-ethanol production, traditional clostridia fermentation is discussed. Sporulation is probably induced by solvent formation, and the molecular mechanism leading to the initiation of sporulation and solventogenesis is also investigated. Different strategies are employed in the metabolic engineering of clostridia that aim to enhancing solvent production, improve selectivity for butanol production, and increase the tolerance of clostridia to solvents. However, it will be hard to make breakthroughs in the metabolic engineering of clostridia for butanol production without gaining a deeper understanding of the genetic background of clostridia and developing more efficient genetic tools for clostridia. Therefore, increasing attention has been paid to the metabolic engineering of E. coli for butanol production. The importation and expression of a non-clostridial butanol-producing pathway in E. coli is probably the most promising strategy for butanol biosynthesis. Due to the lower butanol titers in the fermentation broth, simultaneous fermentation and product removal techniques have been developed to reduce the cost of butanol recovery. Gas stripping is the best technique for butanol recovery found so far.
Zheng
Yan-Ning
YN
Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, 266071 Qingdao, China. zhengyn@qibebt.ac.cn
Li
Liang-Zhi
LZ
Xian
Mo
M
Ma
Yu-Jiu
YJ
Yang
Jian-Ming
JM
Xu
Xin
X
He
Dong-Zhi
DZ
D001674:Bioelectric Energy Sources; D000440:Butanols / Q000378:metabolism*; D046969:Clostridium acetobutylicum / Q000235:genetics / Q000378:metabolism*; D046970:Clostridium beijerinckii / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D005285:Fermentation; D005818:Genetic Engineering / Q000379:methods; D007218:Industrial Microbiology / Q000379:methods*; D012997:Solvents / Q000378:metabolism*
D000440:Butanols; D012997:Solvents