Enhanced Reducing Equivalent Generation for 1,3-Propanediol Production Through Cofermentation of Glycerol and Xylose by Klebsiella pneumoniae

1,3-Propanediol (1,3-PD) biosynthesis plays a key role in NADH consumption to regulate the intracellular reducing equivalent balance of Klebsiella pneumoniae. This study aimed to increase reducing equivalent for enhancing 1,3-PD production through cofermentation of glycerol and xylose. Adding xylose as cosubstrate resulted in more reducing equivalent generation and higher cell growth. In batch fermentation under microaerobic condition, the 1,3-PD concentration, conversion from glycerol, and biomass (OD(600)) relative to cofermentation were increased significantly by 9.1%, 20%, and 15.8%, respectively. The reducing equivalent (NADH) was increased by 1-3 mg/g (cell dry weight) compared with that from glycerol alone. Furthermore, 2,3-butannediol was also doubly produced as major byproduct. In fed-batch fermentation with xylose as cosubstrate, the final 1,3-PD concentration, conversion from glycerol, and productivity were improved evidently from 60.78 to 67.21 g/l, 0.52 to 0.63 mol/mol, and 1.64 to 1.82 g/l/h, respectively.