Flux Enforcement for Fermentative Production of 5-Aminovalerate and Glutarate by <i>Corynebacterium glutamicum</i>

• Main Authors: Carsten Haupka, Baudoin Delépine, Marta Irla, Stephanie Heux, Volker F. Wendisch
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: Catalysts
• Subjects: 5-aminovalerate; glutarate; bioplastics; polyamides; flux enforcement; <i>Corynebacterium glutamicum</i>
• Online Access: https://www.mdpi.com/2073-4344/10/9/1065

Bio-based plastics represent an increasing percentage of the plastics economy. The fermentative production of bioplastic monomer 5-aminovalerate (5AVA), which can be converted to polyamide 5 (PA 5), has been established in <i>Corynebacterium glutamicum</i> via two metabolic pathways. <span style="font-variant: small-caps;">l</span>-lysine can be converted to 5AVA by either oxidative decarboxylation and subsequent oxidative deamination or by decarboxylation to cadaverine followed by transamination and oxidation. Here, a new three-step pathway was established by using the monooxygenase putrescine oxidase (Puo), which catalyzes the oxidative deamination of cadaverine, instead of cadaverine transaminase. When the conversion of 5AVA to glutarate was eliminated and oxygen supply improved, a 5AVA titer of 3.7 ± 0.4 g/L was reached in microcultivation that was lower than when cadaverine transaminase was used. The elongation of the new pathway by 5AVA transamination by GABA/5AVA aminotransferase (GabT) and oxidation by succinate/glutarate semialdehyde dehydrogenase (GabD) allowed for glutarate production. Flux enforcement by the disruption of the <span style="font-variant: small-caps;">l</span>-glutamic acid dehydrogenase-encoding gene <i>gdh</i> rendered a single transaminase (GabT) in glutarate production via the new pathway responsible for nitrogen assimilation, which increased the glutarate titer to 7.7 ± 0.7 g/L, i.e., 40% higher than with two transaminases operating in glutarate biosynthesis. Flux enforcement was more effective with one coupling site, thus highlighting requirements regarding the modularity and stoichiometry of pathway-specific flux enforcement for microbial production.