Boosting microbial dextran production through moderate-intensity pulsed electric field (MI-PEF) treatments

Exopolysaccharides (EPS) produced by lactic acid bacteria (LAB), particularly dextran from Leuconostoc mesenteroides , possess valuable technological and bioactive properties, supporting their wide industrial use. However, conventional fermentation often yields insufficient quantities to meet demand. This study assessed the potential of moderate-intensity pulsed electric fields (MI-PEF) as a novel approach to enhance dextran production by L. mesenteroides DSA_O. Cells were harvested at mid-exponential phase and exposed to MI-PEF treatments before fermentation. Viability, colony morphology, EPS yield, and cell surface structure were evaluated. MI-PEF did not significantly reduce viability, though smaller colonies on solid media suggested a sub-lethal physiological effect. EPS yield increased proportionally to treatment intensity, reaching 40.19 ± 0.36 g/L, a more than sevenfold increase compared to the untreated inoculum. Confocal laser scanning microscopy revealed enhanced EPS accumulation at the cell surface, while scanning electron microscopy indicated marked alterations in cell envelope morphology, pointing to MI-PEF-induced structural remodeling. Preliminary NMR analysis confirmed that dextran branching degree and MW remained unchanged, ensuring preservation of its established functional and technological characteristics. These results indicate that MI-PEF can stimulate microbial metabolism to substantially increase EPS production without compromising cell viability or altering product quality. This study provides the first demonstration of MI-PEF as an effective tool to boost dextran biosynthesis in L. mesenteroides , offering a cost-effective, scalable, and resource-efficient solution to meet industrial EPS demand. • First report of MI-PEF applied to Leuconostoc mesenteroides for dextran production. • MI-PEF pre-treatment increased dextran yield over sevenfold to gram-per-liter scale. • No effect on viability or growth; possible sub-lethal physiological impact detected. • The structure of EPS was not affected by MI-PEF.