Metabolic network analysis of biobutanol production using Clostridium acetobutylicum

Biofuel production from renewable resources is being demanded due to petroleum dependency and continuous depletion of petroleum oil reservoirs. After knowing the applications of biobutanol as biofuel, its economical production is the challenge for researchers. There is two phased (acidogenesis and solventogenesis) metabolism network of Clostridium acetobutylicum has been studied. It is believed that solventogenesis phase of Clostridium acetobutylicum metabolism is key phase in biobutanol production. During solventogenesis, butanol, ethanol, and acetone are produced in acetone-butanol-ethanol (ABE) fermentation and bacteria uptake the acids (butyrate and acetate) produced in acidogenesis phase. Additionally, ethanol can be produced separately from butanol and acetone and with lowest yield. The uptake of acids and the formation of acetone are coupled and there cannot be any uptake of acetate and butyrate without the formation of an equivalent amount of acetone. We have performed metabolic network analysis of this organism using elementary mode analysis. Metabolic network analysis suggests that butanol synthesis is always coupled with acetone production. The gene, namely acetoacetate decarboxylase (adc) is responsible for the synthesis of acetone producing enzymes which can be engineered to enhance butanol production. We also studied the optimal solution space for biobutanol production which will help to understand the optimal feeding strategy semi-batch fermentation process.by M. Kumar and Kalyan Gaye