Simultaneous utilization of d-cellobiose, d-glucose, and d-xylose by recombinant Corynebacterium glutamicum under oxygen-deprived conditions

Abstract

Corynebacterium glutamicum R was metabolically engineered to broaden its sugar utilization range to D-xylose and D-cellobiose contained in lignocellulose hydrolysates. The resultant recombinants expressed Escherichia coli xylA and xylB genes, encoding D-xylose isomerase and xylulokinase, respectively, for D-xylose utilization and expressed C. glutamicum R bglF317A and bglA genes, encoding phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) beta-glucoside-specific enzyme IIBCA component and phospho-beta-glucosidase, respectively, for D-cellobiose utilization. The genes were fused to the non-essential genomic regions distributed around the C. glutamicum R chromosome and were under the control of their respective constitutive promoter trc and tac that permitted their expression even in the presence of D-glucose. The enzyme activities of resulting recombinants increased with the increase in the number of respective integrated genes. Maximal sugar utilization was realized with strain X5C1 harboring five xylA-xylB clusters and one bglF317A-bglA cluster. In both D-cellobiose and D-xylose utilization, the sugar consumption rates by genomic DNA-integrated strain were faster than those by plasmid-bearing strain, respectively. In mineral medium containing 40 g l(-1) D-glucose, 20 g l(-1) D-xylose, and 10 g l(-1) D-cellobiose, strain X5C1 simultaneously and completely consumed these sugars within 12 h and produced predominantly lactic and succinic acids under growth-arrested conditions.