Journal of Microbiology

Research Support, Non-U.S. Gov'ts

NOTE] Effects of Nutritional Enrichment on the Production of Acetone-Butanol-Ethanol (ABE) by Clostridium acetobutylicum: Sung Jun Choi , Joungmin Lee , Yu-Sin Jang , Jin Hwan Park , Sang Yup Lee , In Ho Kim; J. Microbiol. 2012;50(6):1063-1066. Published online December 30, 2012; DOI: https://doi.org/10.1007/s12275-012-2373-1

Abstract: Clostridium acetobutylicum is an industrially important organism that produces acetone-butanol-ethanol (ABE). The main objective of this study was to characterize the effects of increased cell density on the production of ABE during the phase transition from acidogenesis to solventogenesis in C. acetobutylicum. The increased ABE productivity of C. acetobutylicum was obtained by increasing the cell density using a newly designed medium (designated C. acetobutylicum medium 1; CAM1). The maximum OD600 value of C. acetobutylicum ATCC 824 strain obtained with CAM1 was 19.7, which is 1.8 times higher than that obtained with clostridial growth medium (CGM). The overall ABE productivity obtained in the CAM1-fermetation of the ATCC 824 strain was 0.83 g/L/h, which is 1.5 times higher than that (0.55 g/L/h) obtained with CGM. However, the increased productivity obtained with CAM1 did not result in an increase in the final ABE titer, because phase transition occurred at a high titer of acids.

Enhancement of Butanol Tolerance and Butanol Yield in Clostridium acetobutylicum Mutant NT642 Obtained by Nitrogen Ion Beam Implantation: Xiao-Bo Liu , Qiu-Ya Gu , Xiao-Bin Yu , Wei Luo; J. Microbiol. 2012;50(6):1024-1028. Published online December 30, 2012; DOI: https://doi.org/10.1007/s12275-012-2289-9

Abstract: As a promising alternative biofuel, biobutanol can be produced through acetone/butanol/ethanol (ABE) fermentation. Currently, ABE fermentation is still a small-scale industry due to its low production and high input cost. Moreover, butanol toxicity to the Clostridium fermentation host limits the accumulation of butanol in the fermentation broth. The wild-type Clostridium acetobutylicum D64 can only produce about 13 g butanol/L and tolerates less than 2% (v/v) butanol. To improve the tolerance of C. acetobutylicum D64 for enhancing the production of butanol, nitrogen ion beam implantation was employed and finally five mutants with enhanced butanol tolerance were obtained. Among these, the most butanol tolerant mutant C. acetobutylicum NT642 can tolerate above 3% (v/v) butanol while the wide-type strain can only withstand 2% (v/v). In batch fermentation, the production of butanol and ABE yield of C. acetobutylicum NT642 was 15.4 g/L and 22.3 g/L, respectively, which were both higher than those of its parental strain and the other mutants using corn or cassava as substrate. Enhancing butanol tolerance is a great precondition for obtaining a hyperyield producer. Nitrogen ion beam implantation could be a promising biotechnology to improve butanol tolerance and production of the host strain C. acetobutylicum.

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