Disruption of the acetoacetate decarboxylase gene in solvent-producing Clostridium acetobutylicum increases the butanol ratio.

A possible way to improve the economic efficacy of acetone-butanol-ethanol fermentation is to increase the butanol ratio by eliminating the production of other by-products, such as acetone. The acetoacetate decarboxylase gene (adc) in the hyperbutanol-producing industrial strain Clostridium acetobutylicum EA 2018 was disrupted using TargeTron technology. The butanol ratio increased from 70% to 80.05%, with acetone production reduced to approximately 0.21 g/L in the adc-disrupted mutant (2018adc). pH control was a critical factor in the improvement of cell growth and solvent production in strain 2018adc. The regulation of electron flow by the addition of methyl viologen altered the carbon flux from acetic acid production to butanol production in strain 2018adc, which resulted in an increased butanol ratio of 82% and a corresponding improvement in the overall yield of butanol from 57% to 70.8%. This study presents a general method of blocking acetone production by Clostridium and demonstrates the industrial potential of strain 2018adc.