Bacillus subtilis-Derived Postbiotics as a Multifunctional Bio-Catalyst for Enhancing Lactic Acid Bacteria Viability and Yogurt Quality

Abstract

This study demonstrates that Bacillus subtilis GDAAS-A32-derived postbiotics (BSP) enhance yogurt production by optimizing lactic acid bacteria (LAB) viability and functionality. BSP enhanced the growth kinetics and biomass accumulation of Streptococcus thermophilus and Lactobacillus bulgaricus in both an anaerobic and aerobic pure system. The addition of BSP significantly increased the viable cell counts of S. thermophilus and L. bulgaricus, milk-clotting activity, sensory properties, and extracellular polysaccharide content and improved the rheological properties. Moreover, BSP elevated viable counts of S. thermophilus and L. bulgaricus to 6.18 × 108 CFU/g and 1.03 × 108 CFU/g, respectively, by day 7—representing 11.3-fold and 9.3-fold increases versus controls at 20% supplementation. Metabolomic signatures confirmed peptidoglycan reinforcement and flavor enhancement. Mechanistically, BSP supplementation might reduce urate and H2O2 toxicity through NH3-mediated proton neutralization and oxygen scavenging, while establishing a pyrimidine salvage network and redirecting one-carbon metabolism, resulting in enhanced stress tolerance and significant improvements in bacterial viability.