Symbiotic performance of Bacillus coagulans: inhibition of Escherichia coli in coculture and organic-acid/2,3-butanediol production

Abstract Bacillus coagulans is a spore-forming bacterium used as a probiotic and valued for its resistance during processing and storage, although the mechanisms underlying the probiotic effects of Bacillus spp. remain incompletely understood. This study evaluated whether B . coagulans , combined with different prebiotic substrates, suppresses the intestinal competitor Escherichia coli and characterized fermentation products by NMR spectroscopy. In agar diffusion assays, B. coagulans produced larger inhibition zones against E. coli than the tested Lactobacillus strains (10.30 ± 0.06 mm). In coculture, E. coli growth was consistently reduced in the presence of B. coagulans across all prebiotics. Inulin supported the highest B. coagulans viability (10.78 log CFU/mL) and the greatest organic-acid accumulation after 5 days, with acetate as the predominant product (21.0 g/L). The detection of 2,3-butanediol indicates metabolic versatility and suggests a potential route for future biotechnological exploration; however, yield, purity, scalability, and safety must be further evaluated before industrial application. Overall, these findings support B. coagulans as a food-grade probiotic and a promising microbial platform for producing industrially relevant metabolites.