Comparative effects of the single and binary probiotics of Lacticaseibacillus casei Zhang and Bifidobacterium lactis V9 on the growth and metabolomic profiles in yogurts

In the present study, comparative effects of the single and binary probiotics of Lacticaseibacillus casei Zhang (L. casei Zhang) and Bifidobacterium lactis V9 (B. lactis V9) on the growth and metabolomic profiles during milk fermentation and storage has been analyzed using gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS). The growth of B. lactis V9 can be significantly increased (p < 0.001) by co-cultivation with L. casei Zhang at the end of fermentation and storage 10 days, and valine, leucine and isoleucine biosynthesis may be a major contributor to the growth promotion of B. lactis V9. However, the growth of L. casei Zhang was not affected by co-cultivation with B. lactis V9. There were notable distinctions in volatile and non-volatile metabolomic profiles and pathways between the single and binary probiotics cultures; binary probiotics L. casei Zhang and B. lactis V9 significantly affected the volatile, non-volatile metabolic profiles compared to the single probiotics. The levels of acetic acid, hexanoic acid, butanoic acid and pentanoic acid were significantly higher (p < 0.05) in binary probiotics cultures compared to the single probiotic cultures at the storage 10 days, which indicates that binary probiotics had additive effects on the production of short-chain fatty acids during storage. This work provides a detailed insight into metabolomic profiles and growth that differ between the single and binary probiotics cultures, and it can be helpful to develop probiotic yogurt with high probiotic viability and distinct metabolomic profiles.