Butanol is not only an important chemical feedstock but also expected to become a new generation biofuel. Thus, biological butanol production using renewable feedstocks has attracted renewed attention due to the worries of global oil supply and its impact on social and economic development. However, compared with petrochemical-derived butanol, biological butanol production is still not economically competition, because of its major drawbacks: high cost of the feedstocks, low butanol concentration in the fermentation broth and the co-production of low-value byproducts acetone and ethanol. Recently, Shanghai cooperative bio-butanol group (SCBG) developed a simple-to-complex technical route to improve bio-butanol production with a focus on: increasing butanol ratio in the solvent through metabolic engineering of Clostridia spp.; introducing and optimizing the butanol synthetic pathway in the species with high butanol tolerance; overcoming the glucose repression effect to utilize low-cost non-grain based feedstocks. SCBG believes that, through extensive domestic and international industry-university-research cooperation, a sustainable and economically viable process for biological butanol production can be established in the near future.
Biofuels ; Butanols ; metabolism ; Clostridium ; genetics ; metabolism ; Clostridium beijerinckii ; genetics ; metabolism ; Fermentation ; Genetic Engineering ; methods ; Industrial Microbiology ; methods ; trends

Solventogenic clostridia are important industrial microorganisms. Optimization of the fermentation performance of solventogenic clostridia, through genetic modification, has always been considered as the main topic involved in solvents production. However, due to the incomplete genetic tools, no research breakthroughs have been achieved. In recent years, with the development of new technologies and methods (e.g. TargeTron gene knockout, large DNA fragment integration method), great progresses have been made towards genetic engineering solventogenic clostridia. In this review, we summarize the development of the genetic tools for solventogenic clostridial species, and simultaneously point out the shortages of the existing technologies in efficiency and comprehensiveness. Therefore, optimization of the existing technologies in gene inactivation in clostridia, such as establishing homologous exchange-based gene deletion and exchange, is still imperative; and in parallel, new genetic tools (e.g. multiplex genome editing, targeted or random multi-copy gene integration) should also be timely developed.
Acetone ; metabolism ; Butanols ; metabolism ; Clostridium ; genetics ; metabolism ; Clostridium acetobutylicum ; genetics ; metabolism ; Clostridium beijerinckii ; genetics ; metabolism ; Ethanol ; metabolism ; Fermentation ; Genetic Engineering ; methods ; Industrial Microbiology ; methods ; Solvents ; metabolism