Characterization of plasmalogen production in facultative anaerobic bacteria and aerobic synthesis in recombinant Escherichia coli expressing anaerobic bacterium-derived plasmalogen synthase genes.

Plasmalogens are glycerophospholipids with vital physiological functions, conferring antioxidant properties and contributing to membrane stabilization. While plasmalogen synthase genes plsA and plsR were identified in the obligate anaerobic bacterium Clostridium perfringens, plasmalogen production has not been reported in facultative anaerobes, in which a single gene commonly encodes plsA. To establish a cost-effective microbial plasmalogen production system, we screened 38 lactic acid bacterial strains and identified 11 plasmalogen producers, with Enterococcus faecalis K-4 exhibiting the highest productivity. Optimization of culture conditions, including the substitution of glucose with lactose and the addition of soy-derived peptides, increased plasmalogen production by 1.5-fold. Heterologous expression of plasmalogen synthesis genes from E. faecalis K-4, Lactococcus cremoris ATCC BAA-493, C. perfringens HN13, and Bifidobacterium longum in Escherichia coli BL21(DE3) confirmed plasmalogen biosynthesis in all strains. Recombinant PlsA from facultative anaerobic L. cremoris ATCC BAA-493 exhibited superior oxygen tolerance, enabling high plasmalogen production under aerobic conditions. Structural analysis via liquid chromatography-tandem mass spectrometry revealed consistent plasmalogen species (PE-Pls 16:0/17:0CP, 16:0/19:0CP, and 19:0/17:0CP) across strains and conditions. Plasmalogen-producing E. coli recombinants demonstrated enhanced oxidative and osmotic stress resistance, with plasmalogen-expressing cells exhibiting significantly reduced reactive oxygen species accumulation and improved growth in 1.0 M NaCl. Structural modeling using AlphaFold3 indicated that the C-terminal α-helix of L. cremoris PlsA contributes to its oxygen tolerance. These findings highlight the potential of facultative anaerobic bacteria, particularly L. cremoris ATCC BAA-493, for scalable plasmalogen production and underscore the functional benefits of plasmalogens in enhancing stress resilience. IMPORTANCE: Plasmalogens are essential glycerophospholipids with crucial physiological functions, including membrane stabilization and antioxidant activity. Recently, supplements that support brain function have gained considerable attention but are expensive due to their extraction from animal tissues and marine sources. In this study, we identified facultative anaerobic bacteria as a cost-effective source for plasmalogen production, offering an accessible strategy to introduce plasmalogens into the diet. Additionally, introducing plasmalogen biosynthetic genes into Escherichia coli presents a promising approach for large-scale, efficient plasmalogen production. Notably, for the first time, we achieved aerobic plasmalogen production using recombinant E. coli harboring plasmalogen biosynthetic genes from Lactococcus cremoris. We hypothesize that the enhanced oxygen tolerance of L. cremoris plasmalogen synthase, potentially due to a protective mechanism that prevents oxidative degradation of the [4Fe-4S] cluster, enhances this aerobic production.