Process optimization of metabolically engineered Escherichia coliNSK015 fermentation for progressive improvement of 1,3‐propanediol production

Abstract BACKGROUND Previously, Escherichia coli NSK015 was developed for high yield of 1,3‐propanediol (1,3‐PDO) production. To further improve 1,3‐PDO concentration, parameters including k L a values with different agitations and impeller numbers, concentrations of coenzyme B12 and feeding strategies during fed‐batch fermentation were investigated. RESULTS In this study, aerobic conditions at 300 rpm agitation and 1 vvm aeration with two Rushton turbine impellers ( k L a = 33.6 h −1 ) and the concentration of coenzyme B12 at 7.5 μmol L −1 were identified as the best optimized conditions to improve 1,3‐PDO production by the strain. With a two‐pulsed continuous feeding, E. coli NSK015 produced 1,3‐PDO up to 60.3 g L −1 with the 1,3‐PDO yield approaching a theoretical maximum of 0.97 g g −1 and productivity of 0.42 g L −1 h −1 in fed‐batch fermentation, in which concentration was improved about 60% compared to that of batch fermentation. CONCLUSION The result indicated the efficiency of E. coli NSK015 in producing 1,3‐PDO under optimal aerobic conditions. The strain could even enhance growth and maintain enzymatic activities involved in the 1,3‐PDO pathway without utilizing antibiotics, isopropyl β‐ d ‐1‐thiogalactopyranoside (IPTG) or enriching nutrients. Plasmid instability, high production cost related to medium preparation and purification, and waste disposal were not of concern. This may provide a new insight for large‐scale 1,3‐PDO production by E. coli NSK015. Additionally, E. coli NSK015 could be a microbial host model for further developing new 1,3‐PDO‐producing microorganisms regardless of plasmid, inducer, antibiotics and rich nutrients in fermentation medium. © 2023 Society of Chemical Industry (SCI).