Highly efficient fermentation of glycerol and 1,3-propanediol using a novel starch as feedstock

Abstract

As a potential cost-effective feedstock for highly efficient fermentation of glycerol and its downstream product 1,3-propanediol (1,3-PD), duckweed starch was characterized and used for glycerol fermentation, for the first time, in this study. Genes involved in glycerol biosynthesis (gpd1 and gpp2) were overexpressed in Escherichia coli, and genes involved in glycerol catabolism (glpK and gldA) were disrupted, which led to significantly decreased residual sugar levels and dramatically increased glycerol production. The maximum glycerol concentration in fed-batch fermentation reached 102.72 g L-1 at 28 h, and the glycerol productivity was 3.67 g L-1 h-1, which, to our knowledge, is the highest productivity thus far reported. Subsequently, glycerol broth was fermented into 1,3-PD by Klebsiella pneumoniae. The concentration, conversion rate and productivity of 1,3-PD reached 35.54 g L-1, 40.28% and 0.89 g L-1 h-1, respectively, without optimization. In summary, the duckweed starch-to-glycerol-to-1,3-PD process is feasible and shows potential for improving glycerol industry competitiveness.