Combined overexpression of genes involved in pentose phosphate pathway enables enhanced D-xylose utilization by Clostridium acetobutylicum.

D-Xylose utilization by Clostridium acetobutylicum, an important industrial microorganism used in ABE (Acetone, Butanol and Ethanol) production, has attracted increasing interests. We demonstrated previously that co-overexpression of genes, encoding d-xylose symporter, D-xylose isomerase and xylulokinase, improved D-xylose utilization by C. acetobutylicum (Xiao, H., et al., 2011. Applied and Environmental Microbiology 77, 7886-7895). Here, we further identified genes involved in PPP (Pentose Phosphate Pathway) in C. acetobutylicum and evaluated their contribution to d-xylose utilization. Among all the candidate genes, the CAC1347, CAC1348, CAC1730 and CAC2880 were validated to encode genes tal, tkl, rpe and rpi, four key genes involved in PPP, respectively. The following combined overexpression of these genes conferred a significantly improved xylose-utilizing ability to the recombinant strain, reaching a solvent titer 42% higher than that of the wild-type strain. This finding offers a useful strategy to optimize d-xylose utilization by C. acetobutylicum.