Engineering Corynebacterium glutamicum for efficient production of succinic acid from corn stover pretreated by concentrated-alkali under steam-assistant conditions

Corynebacterium glutamicum was developed for efficient production of succinic acid from corn stover (CS) pretreated by concentrated-alkali under steam-assistant (CASA) conditions. First, C. glutamicum was engineered by 1) blocking the by-products pathways (deletion of ldh, pta-ackA, and cat), 2) enhancing the carbon flux to succinate (overexpression of pyc and ppc), and 3) releasing the end-product inhibition (overexpression of Ncgl0275). The recombinant strain produced 117.8 g/L succinate in fed-batch fermentation. Second, to fully utilize xylose in lignocellulosic hydrolysate, two xylose utilization pathways-the isomerase pathway and the Weimberg pathway-were introduced into the recombinant strain. Third, CS was pretreated by CASA with a higher sugars yield and a lower black liquid. Finally, 64.16 g/L of succinic acid was obtained from 150 g/L CASA-pretreated CS by engineered C. glutamicum. These results showed a succinate high-producing C. glutamicum strain using glucose and xylose simultaneously as well as an effective and environmentally acceptable pretreatment strategy.