Metabolic Engineering of High L-Lysine-Producing Escherichia coli for de Novo Production of L-Lysine-Derived Compounds.

ABSTRACT

5-Aminovalerate (5-AVA), 5-hydroxyvalerate (5-HV), and 1,5-pentanediol (1,5-PDO) are l-lysine derivatives with extensive applications in the production of materials such as polyesters, polyurethane, plasticizers, inks, and coatings. However, their large-scale production is limited by the lack of efficient synthetic pathways. Here, we aimed to construct multiple synthetic pathways by screening the key enzymes involved in the synthesis of these compounds in Escherichia coli. The engineered pathway utilizing RaiP demonstrated a superior catalytic efficiency. The LER strain that overexpressed only raiP successfully synthesized 9.70 g/L 5-HV and 8.31 g/L 5-AVA, whereas the strain LERGY that overexpressed raiP, gabT, and yahK accumulated 9.72 g/L 5-HV and 7.95 g/L 5-AVA from 20 g/L glucose. The introduction of exogenous transaminases and dehydrogenases enhanced cell growth and fermentation efficiency with respect to 5-HV synthesis, albeit without significantly impacting the yield. Strain LE05, incorporating only two exogenous enzymes, RaiP and CaR, produced 1.87 g/L 1,5-PDO, 3.85 g/L 5-HV, and 4.78 g/L 5-hydroxyglutaraldehyde from 20 g/L glucose after 6 days. The strain LE02G, fortified with transaminase, dehydrogenase, and NADPH regeneration system, accumulated 7.82 g/L 1,5-PDO, whereas the aldp-knock out LE02G2 synthesized 10.98 g/L 1,5-PDO from 50 g/L glucose in fed-batch fermentation after 6 days, yielding 0.22 g/g glucose (0.37 mol/mol). Introducing the NADPH regeneration pathway and deleting the NADPH-consuming pathways increased the 1,5-PDO yield and decreased the precursor concentration. The proposed pathways and engineering strategies presented in this study can prove instrumental in developing biological routes for the practical production of 5-AVA, 5-HV, and 1,5-PDO.