Fermentation Optimization and In-Vitro Antioxidant Activity of Exopolysaccharides Produced by Leuconostoc suionicum LSBM1 Using Sugar Beet Molasses

The purpose of this study was to screen for high-yield exopolysaccharide (EPS) producing lactic acid bacteria (LAB) from sugar beet molasses and to evaluate the production capacity of EPS using sugar beet molasses. A highly EPS-producing LAB strain LSBM1 isolated from sugar beet molasses was identified, and the fermentation conditions for EPS using sugar beet molasses as the substrate were optimized by the single-factor experiment and response surface methodology. Strain LSBM1 was identified as Leuconostoc suionicum based on morphological characteristics, and 16S rRNA gene sequence analysis. The optimal culture medium for EPS production was composed of 300 g/L beet molasses, 20.0 g/L yeast extract, 20.0 g/L K₂HPO₄·3H₂O, 0.01 g/L MgSO₄·7H₂O, 0.01 g/L NaCl, 0.01 g/L CaCl₂, 0.01 g/L MnSO₄·H₂O, 0.01 g/L FeSO₄·7H₂O, 0.01 g/L. The maximum EPS yield (31.78 g/L) was achieved under the optimized conditions of loading volume 200 mL/250 mL, inoculum size 2%, initial pH value 8.1, culture temperature of 37.59 °C, and culturing period 38.5 h. The in-vitro antioxidant activity showed that LSBM1 EPS had good scavenging activity against DPPH and ABTS radicals. Together, these results provide a LAB strain and the production conditions for obtaining high EPS yields using sugar beet molasses as substrate, and suggest that the harvested LAB-EPS might have potential applications as functional ingredients in the food industry.