Improving CoQ 10 productivity by strengthening glucose transmembrane of Rhodobacter sphaeroides

Background Several Rhodobacter sphaeroides have been widely applied in commercial CoQ 10 production, but they have poor glucose use. Strategies for enhancing glucose use have been widely exploited in R. sphaeroides . Nevertheless, little research has focused on the role of glucose transmembrane in the improvement of production. Results There are two potential glucose transmembrane pathways in R. sphaeroides ATCC 17023: the fructose specific-phosphotransferase system (PTS Fru , fruAB ) and non-PTS that relied on glucokinase ( glk ). fruAB mutation revealed two effects on bacterial growth: inhibition at the early cultivation phase (12–24 h) and promotion since 36 h. Glucose metabolism showed a corresponding change in characteristic vs. the growth. For Δ fruA Δ fruB , maximum biomass ( Bio max ) was increased by 44.39% and the CoQ 10 content was 27.08% more than that of the WT. glk mutation caused a significant decrease in growth and glucose metabolism. Over-expressing a galactose:H + symporter ( galP ) in the Δ fruA Δ fruB relieved the inhibition and enhanced the growth further. Finally, a mutant with rapid growth and high CoQ 10 titer was constructed (Δ fruA Δ fruB / tac :: galP OP ) using several glucose metabolism modifications and was verified by fermentation in 1 L fermenters. Conclusions The PTS Fru mutation revealed two effects on bacterial growth: inhibition at the early cultivation phase and promotion later. Additionally, biomass yield to glucose ( Y b/glc ) and CoQ 10 synthesis can be promoted using fruAB mutation, and glk plays a key role in glucose metabolism. Strengthening glucose transmembrane via non-PTS improves the productivity of CoQ 10 fermentation.