Highly efficient production of 1,3-propanediol by CRISPR-Cas12a-edited Klebsiella pneumoniae using glycerol and lignocellulosic hydrolysate as co-substrates.

Abstract

Efficient biosynthesis of 1,3-PDO, a key bio-based chemical, depends on precise regulation of the host metabolic network. In this study, a heterologous CRISPR-Cas12a genome editing system was established and systematically optimized in Klebsiella pneumoniae, enabling efficient and stable genome editing (75-100% efficiency). Using on this platform, by-product pathways were reduced through multi-gene deletions (frdA, poxB, adhE, ldhA, glpK, ptsG and dhaM) to enhance the yield of 1,3-PDO from glycerol. By heterologously expressing GPD1/GPP2 and optimizing promoter, a metabolic network for the "glucose-glycerol-1,3-PDO" pathways was reconstructed. Cometabolism studies indicated that low concentrations of xylose and arabinose as co-substrates enhanced conversion efficiency of glycerol, whereas glucose alleviated metabolic competition. Under cometabolism of glucose and glycerol, the engineered strain K. pneumoniae S2 ΔABEAKGM-1-2 produced 1003.7 mmol/L (76.4 g/L) of 1,3-PDO with a yield of 0.83 mol/mol glycerol, an overall molar yield of 0.78 mol/mol based on total substrate consumption, and a productivity of 27.9 mmol/L/h. When lignocellulosic hydrolysate was used as co-substrate, 981.1 mmol/L (74.7 g/L) of 1,3-PDO was produced with a yield of 0.77 mol/mol glycerol and a productivity of 27.3 mmol/L/h. This study achieved efficient redirection of carbon flux toward 1,3-PDO through systematic metabolic engineering, providing valuable strain resources and technical guidance for the sustainable and cost-effective biomanufacturing of bio-based 1,3-PDO.