Regulation of ρ-coumaric acid tolerance in Clostridium beijerinckii by disturbing the intracellular electron transport chain

ρ-coumaric acid with strong antibacterial activity is produced during the pretreatment and hydrolysis of lignocellulosic biomass to monomeric sugars. The cell growth and metabolism of C. beijerinckii NCIMB 8052 is significantly inhibited by ρ-coumaric acid. In this study, adaptation of C. beijerinckii NCIMB 8052 to ρ-coumaric acid was remarkably enhanced after disruption of the intracellular electron transport chain, and the antibacterial activity assay showed a 2-fold increase in cell viability in the presence of 0.5 g/L ρ-coumaric acid 24 h after inoculation. Additionally, electricity generation in the wild-type and recombinant strains was measured using microbial fuel cell devices, and the intracellular levels of co-factor NAD(P)H were determined by the enzyme cycling method to show disturbed intracellular electron transfer after disruption of gene Cbei_2996. Furthermore, the metabolism of ρ-coumaric acid by C. beijerinckii was analyzed. These data indicated that gene Cbei_2996 plays a significant role in regulating ρ-coumaric acid tolerance in C. beijerinckii; the metabolism of ρ-coumaric acid mainly coupled with co-factor NADH is catalyzed by reductase. The strategy used in this study provides a potential approach for producing dominant microorganisms with high inhibitor tolerance for butanol production using renewable lignocellulosic materials.