Production of γ-aminobutyric acid using corncob residue as carbohydrate feedstock by engineered Corynebacterium glutamicum

This study investigated Corynebacterium glutamicum for GABA production using corncob residue, a cheap carbon source, as carbohydrate feedstock instead of grains. Current fermentative production of γ-aminobutyric acid (GABA) mainly relies on starch and sugar feedstocks. Therefore, the use of cheap carbon sources can effectively reduce the production costs of GABA. This study validated the feasibility of an available non-food lignocellulose feedstock, corncob residue, for GABA fermentation. An engineered C. glutamicum was constructed by secretory expression of glutamate decarboxylase gadBmut and knock-out the GABA biodegradation gene. The fermentation parameters in shake flasks and bioreactors were optimized including the sugar concentration, nitrogen levels, cofactor levels and aeration rate, and fermentation mode. The fed-batch fermentation of the concentrated corncob residue hydrolysate achieved a record high GABA production of 93.15 g/L from lignocellulosic feedstock with a yield of 0.43 g/g glucose. The results provided technical support for the industrial production of GABA from low-cost lignocellulosic carbohydrates.