Optimization of fermentation medium for advancing postbiotic antibacterial activity

Antimicrobial postbiotic compounds have attracted increasing interest due to their potential applications in the food industry, particularly as candidates for biopreservation strategies. From a technological perspective, process optimization represents a valuable strategy for improving the production of postbiotic compounds and supporting the development of efficient fermentation bioprocesses. This study aimed to optimize the culture medium to enhance the antibacterial activity of a postbiotic derived from Pediococcus acidilactici CECT 9879. Plackett-Burman design (PBD) was first used to screen carbon and nitrogen sources, followed by one-factor-at-a-time (OFAT) experiments to evaluate yeast-derived ingredients and MRS-derived basal medium components, and response surface methodology based on a central composite design (CCD-RSM) for final medium optimization. Significant linear, quadratic, and interaction effects of key medium components, particularly yeast-derived ingredients and sodium acetate, were identified, indicating well-defined optimal concentration ranges. Under optimized composition, the minimum inhibitory concentration (MIC) against Escherichia coli decreased from 48.33 ± 2.89% (v/v) in the non-optimized medium to 31.67 ± 2.89% (v/v). The results highlight the role of nutrient optimization in modulating postbiotic antibacterial activity during fermentation and provide insights that may contribute to improving process efficiency in the agri-food sector.