Improvement of 1,3-propanediol production from glycerol using formate as an intermediary metabolite for NADH regeneration in Klebsiella oxytoca

1,3-Propanediol (PDO) is a value-added chemical used widely in cosmetics, foods, lubricants, adhesives, and pharmaceuticals. Klebsiella oxytoca is a facultative anaerobe that can produce 1,3-PDO through the fermentation pathway of glycerol. Recently, formate produced (bio)electrochemically from CO2 has been highlighted as an intermediary metabolite and environmentally friendly biological reducing agent for bioconversion. This study examined how the glycerol fermentation of K. oxytoca with various formate concentrations enhances 1,3-PDO production. Glycerol consumption increased from 58.7 % to 92.6 %, while the 1,3-PDO titer was improved simultaneously from 172.5 to 251.0 mM using 50 mM of formate. During 1,3-PDO production, the NADH pool increased to 345.3 nM/OD600, 2.4 times higher than the control. Therefore, adding formate to glycerol fermentation reduces the residual glycerol and increases 1,3-PDO production simultaneously, which can be an alternative bioconversion strategy without genetic modification.