Optimization of Media Composition to Maximize the Yield of Exopolysaccharides Production by Lactobacillus rhamnosus Strains

Growth media composition is a critical factor influencing the yield of bacterial exopolysaccharides (EPSs), which have attracted the interest of researchers around the world due to their diverse physicochemical and biological properties. This work presents the optimization of media for EPS synthesis by three Lactobacillus rhamnosus strains, namely ŁOCK 0943, ŁOCK 0935, and OM-1. The optimized media led to a more than 13-fold increase in EPS yield for L. rhamnosus ŁOCK 0943 (from 85 to 1138.2 mg/L), an almost 9-fold increase for L. rhamnosus ŁOCK 0935 (from 103.67 to 900 mg/L), and a more than 7-fold increase for L. rhamnosus OM-1 (from 133.67 to 987.84 mg/L) as compared to cultures in standard MRS medium (de Man, Rogosa, and Sharpe). It has been found that the main medium-related determinant of EPS synthesis by the studied L. rhamnosus strains are the carbon source—in this case, it was fructose and sucrose.