Systems metabolic engineering of Klebsiella pneumoniae for high-level 1,3-propanediol production.

1,3-Propanediol (1,3-PDO) is an essential monomer used in the synthesis of polytrimethylene terephthalates. However, the microbial production of 1,3-PDO is limited by product tolerance and Vitamin B12 (VB12) supplementation. In this study, FMME-KP-a Klebsiella pneumoniae strain with a 1,3-PDO titer of 63.4 g/L. Through pathway reprogramming, the 1,3-PDO titer of strain FMME-14 was increased by 49.1 %. To enhance strain tolerance, a 1,3-PDO biosensor was developed to screen for high-yield strains during adaptive laboratory evolution. Reverse metabolic engineering of genes ydaML63V and pgaD improved the 1,3-PDO tolerance of strain FMME-38 by 62.5 %, leading to a 15.9 % increase in 1,3-PDO production. By enhancing the supply of cofactors VB12 and NADH, strain FMME-51 produced 138.6 g/L 1,3-PDO, with a yield of 0.52 g/g within 48 h, without the need for external VB12 supplementation. Additionally, this strain produced 122.7 g/L of 1,3-PDO using crude glycerol as a substrate. To the best of our knowledge, this is the highest reported titer and yield of microbial 1,3-PDO production.