Characterization of growth and metabolomic profiles of Lacticaseibacillus paracasei ProSci-92 as a potential probiotic culture in extended milk fermentation

The Lacticaseibacillus paracasei ProSci-92 (ProSci-92) strain was isolated from traditional fermented yak milk in the Shangri-La Tibetan region, China. Initial screening revealed its promising potential for lactose and protein hydrolysis. This study monitored the growth and metabolic dynamics of ProSci-92 and during a 60-h milk fermentation process using nontargeted metabolomics. Fermented milk samples were collected every 12 h, enabling comparative metabolomic profiling at adjacent time points. By the end of fermentation, the viable cell count reached 4.59 × 10⁹ cfu/mL, accompanied by significant changes in acidity (both pH and titratable acidity). ProSci-92 exhibited active growth, particularly within the first 24 h of fermentation. Notably, the metabolic profiles of fermented milk at different fermentation stages were closely correlated with key fermentation characteristics, including pH, titratable acidity, and the viable cell count in Procrustes analysis (M² = 0.4085). Our findings revealed significant enrichment of metabolites and pathways associated with AA metabolism and ABC transporters throughout fermentation. Substantial differences in metabolomic profiles were noted between the start (0 h) and end (60 h) of fermentation, marked by an increase in health-promoting metabolites and nutrients, including essential AA, short-chain fatty acids, organic acids, and purines (variable importance in projection score >1). This study elucidates the dynamic changes in the metabolome during ProSci-92 milk fermentation, providing valuable insights into metabolomic transformations over extended fermentation periods. The findings underscore the potential of ProSci-92 as a beneficial starter culture for enhancing the nutritional and health-promoting attributes of fermented milk beverages.