Screening and Optimization of Lactic Acid Bacteria for High-Yield Exopolysaccharide (EPS) Production for Industrial Application

To identify lactic acid bacteria with high-yield exopolysaccharide (EPS) production potential for industrial applications, this study employed LMM solid medium to screen three strains isolated from sticky and elongated kimchi samples. The EPS production capacity of the strains was quantified using the phenol-sulfuric acid method, leading to the identification of a high-EPS-producing strain, designated as GK-2.Through 16S rDNA sequencing analysis, strain GK-2 was identified as Lactobacillus pseudoenterica GK-2. To further enhance its EPS production, the fermentation conditions for Leuconostoc pseudomesenteroide GK-2 were systematically optimized. Initially, a single-factor experiment was conducted, examining the effects of four key factors: carbon source and its concentration, nitrogen source and its concentration, inoculation amount, and fermentation time. Based on these results, response surface methodology (RSM) was applied to determine the optimal fermentation conditions for maximizing EPS production.The optimal fermentation parameters for L. pseudoenterica GK-2 were established as follows: glucose concentration of 7.51%, inoculation amount of 5.86%, and urea concentration of 3.02%, with a cultivation period of 36 hours. Under these optimized conditions, the EPS yield of L. pseudoenterica GK-2 reached 3.88 g/L, representing a 2.24-fold increase compared to pre-optimization levels. These findings provide a promising basis for the large-scale industrial production of EPS using L. pseudoenterica GK-2.