Efficient Biorefinery Based on Designed Lignocellulosic Substrate for Lactic Acid Production

The current study investigated the feasibility of developing and adopting a few state-ofthe-art fermentation techniques to maximize the efficiency of the lignocellulosic waste bioconversion. There have been various efforts towards utilizing the fermentable sugars released from the specific parts of lignocellulose, i.e., cellulose and hemicellulose. However, complete utilization of carbon sources derived from lignocellulosic biomass remains challenging owing to the generated glucose in the presence of beta-glucosidase, which is known as glucose-induced carbon catabolite repression (CCR). To overcome this obstacle, a novel simultaneous saccharification and fermentation (SSF) of lactic acid was designed by using Celluclast 1.5L as a hydrolytic enzyme to optimize the generation and utilization of pentose and hexose. Under the optimal enzyme loading and pH condition, 53.1 g/L optically pure L-lactic acid with a maximum volumetric productivity of 3.65 g/L/h was achieved during the SSF from the brewer's spent grain without any nutrient supplementation. This study demonstrated the potential of lactic acid production from the designed lignocellulosic substrate.