Comparative Optimization of Culture Media for Enhanced β-Glucan Production by Limosilactobacillus fermentumSH2 (MW897962) and Its Bioactivity Assessment

This study optimized β-glucan production from the local isolate Limosilactobacillus fermentum SH2 (MW897962) and evaluated its bioactivity. Using Response Surface Methodology (RSM) with a Central Composite Design (CCD), exopolysaccharide (EPS) production was optimized in Semi-Defined Media (SDM) and Chemically Defined Media (CDM). Predicted optimal β-glucan yields were 2.42 g/100 mL for PYE and 29.65 g/100 mL for molasses, with molasses doubling EPS production under optimal conditions. The actual EPS yield (950.65 mg/100 mL) exceeded the predicted yield (931.54 mg/100 mL), while cell mass (129.95 mg/100 mL) was slightly lower than predicted (131 mg/100 mL). High R² values for β-glucan production (91.3%) and cell mass (90.2%) validated the optimization model. The β-glucan demonstrated potent bioactivity, including 91% DPPH radical scavenging at 200 μg/mL. Cytotoxicity against Caco-2 colorectal cancer cells showed 85.64% viability at 100 μg/mL, comparable to the β-glucan standard (84.89%). At 1.0 and 10 μg/mL, β-glucan from LAB showed greater inhibition of Caco-2 cell proliferation than the standard. Antibacterial activity against four pathogens revealed the highest inhibition zone (14.00 mm) at 100 mg/mL against Staphylococcus aureus ATCC. This study highlighted the potential of L. fermentum SH2 as a cost-effective source of β-glucan with significant antioxidant, antitumor, and antibacterial properties.