Disruption of hydrogenase gene for enhancing butanol selectivity and production in Clostridium acetobutylicum

Abstract

Butanol production by solventogenic clostridia has long been complicated with the formation of acetone as a main byproduct, which causes a low product yield. Here, although some recent attempts failed to engineer the hydrogenase gene hydA in wild-type Clostridium, we successfully disrupted hydA with a plasmid pSY6 in C. acetobutylicum ATCC 55025. The hydA disrupted strain was able to produce 18.3 % more butanol with by-product acetone decreased by 31.2 %, indicating the inactivation of hydrogenase regulated redox balance for selective inhibition of acetone production. Exogenous supplementation of methyl viologen altered the carbon flux and further reduced acetone formation, with the maximum butanol yield of 0.28 g/g and butanol ratio of 84.0 %, respectively. The similar improvements of butanol yield and ratio were observed with corn stover as carbon source, indicating hydA disrupted strain had the potential for biobutanol production using lignocellulosic biomass. This study provides valuable understanding for regulation of redox and solventogenesis by engineering hydrogenase in Clostridium species towards the advanced production of butanol.