Strain Improvement Of Clostridium Acetobutylicum And Study On Fermentation Technology

The acetone-butanol fermentation is one of the oldest known industrial fermentations. It was ranked second only to ethanol fermentation in its scale of production, and was one of the largest biotechnological processes ever known. However, since the 1950's industrial ABE fermentation has declined continuously. Currently ABE fermentation is becoming more attractive for producing chemicals and liquid fuels due to the exhaustion of natural oil and gas resources. However, being low in both solvent yield and production efficiency makes acetone-butanol fermentation uneconomical. Therefore, the study on breeding of high yield strain and optimization of fermentation technology is absolutely necessary.In this paper, Clostridium acetobutylicum was treated with UV and NTG. A mutant named E-11 was selected. Under the unoptimized fermentation condition, the yield of total solvent was 17.20g/L, inceased by 16% than that of the original strain. The mutant was genetically stable.With solvent production as the main index, the fermentation conditions were optimized: the concentration of corn steep liquor, corn starch, L-Cysteine, temperature, initial pH, and inoculation quantities were1%, 7%, 0.1%, 37℃, 5.2, 8%, respectively. The total solvent yield reached 18.79g/L under the optimized conditions.To improve acetone-butanol production efficiency of Clostridium acetobutylicum, by-products, which were the by-products of fermentation, were added in the fermentation process to investigate the effect of by-products on cell growth, production of acetone–butanol and other by-products. Addition of 1.5g/L acetate could accelerate the cell growth and enhance acetone production. The biggest biomass and final biomass were increased by 9.59% and 12.76%, respectively. And the final concentration of acetone was increased to 6.5 g/L by 20%, while the butanol production couldn't be enhanced. Addition of 2.0 g/L butyric acid could also accelerate cell growth and enhance butanol production. The biggest biomass and final biomass were increased by 3.77% and 3.06%, respectively. And the final concentration of butanol was increased by 11.6 %, reached 12.84 g/L ,while the acetone production couldn't be enhanced.