"Invited Talk" Metabolic Engineering of Clostridium Tyrobutyricum for Butyric Acid Production from Agricultural and Industrial Wastes

Clostridium tyrobutyricum ATCC 25755 is a promising butyric acid-producing strain. However, the relatively high substrate cost, which accounts for ~50% of the overall cost, is limiting the industrial production of bio-based butyric acid. Our research focuses on improving the economic feasibility of butyric acid fermentation via metabolic engineering strategies. For example, sucrose (scrA, scrB and scrK), xylose (xylT, xylA and xlyB) and galactose (galK, galE, galT, and galP) metabolism-related genes from C. acetobutylicum ATCC 824 were successfully overexpressed in C. tyrobutyricum, endowing it with the superior ability to co-utilize mixed sugars in cane molasses (sucrose, fructose and glucose), lignocellulosic hydrolysates (glucose and xylose) and coffee ground hydrolysate (galactose, mannose, and glucose), respectively. In addition, the tolerance of C. tyrobutyricum to the lignocellulosic hydrolysate-derived inhibitors was improved by overexpressing heat shock proteins and short-chain dehydrogenase/reductase, resulting in an enhanced butyrate production. These studies demonstrated the advantages of these metabolic engineering strategies and the feasibility of economic butyric acid production from agricultural and industrial wastes.