Synergistic effects of Lactiplantibacillus plantarum P-8 and Lacticaseibacillus paracasei ProSci-92 in cofermented milk: Metabolomic and physicochemical evaluation

In this study, a novel composite probiotic fermented milk was developed using Lactiplantibacillus plantarum P-8 and Lacticaseibacillus paracasei ProSci-92 strains with promising probiotic properties. Different proportions of the 2 strains were evaluated to identify the optimal coculture ratio. The physicochemical properties, storage stability, viable bacterial counts, and metabolomic profiles of the coculture fermented milk, single-strain fermented milk samples, and a commercial fermented milk (PYS-010) were compared. The results demonstrated that the ProSci-92&P-8 (1,000:1) coculture exhibited a significant synergistic effect. This coculture not only enhanced viable counts, acid production capacity, and water-holding capacity but also markedly improved the texture and flavor characteristics of the fermented milk. Untargeted metabolomic analysis further revealed the positive effect of cofermentation on the accumulation of various characteristic flavor-inducing compounds (acetoin, acetaldehyde, butyric acid, propionic acid, arachidonic acid) and functionally relevant AA (lysine, ornithine, phenylalanine, threonine, valine) in the fermented milk. Glutathione was identified as a potential metabolic biomarker associated with synergistic interactions between the strains. This study provides a theoretical foundation and technical support for developing next-generation fermented dairy products with desirable sensory attributes and health benefits.