Comparison of the effects of single probiotic strains Lactobacillus casei Zhang and Bifidobacterium animalis ssp. lactis Probio-M8 and their combination on volatile and nonvolatile metabolomic profiles of yogurt

There has been a growing interest in cofermentation of starter cultures with probiotics in milk. In this study, we analyzed the effects of adding the single probiotics Lactobacillus casei Zhang (Zhang) or Bifidobacterium animalis ssp. lactis Probio-M8 (M8) or a combination of Zhang and M8 to starter cultures on volatile and nonvolatile metabolomic profiles after 14 d of storage at 4°C and compared using a liquid chromatography-tandem mass spectrometry (LC-MS) and GC-MS-based metabolomics approach. Principal component analysis, heatmap plots, and Spearman correlation results showed that Zhang alone had a greater effect on volatile and nonvolatile metabolomic profiles than M8 alone. The combination of Zhang and M8 had additive effects on the production of metabolites. For volatile metabolites, the levels of acetaldehyde, diacetyl, acetoin, and acetic acid were higher for the combination of Zhang and M8 compared with either single probiotic culture. Significantly increased nonvolatile components induced by adding Zhang were identified were enriched in the galactose, amino- and nucleotide sugar, fructose and mannose, purine, phenylalanine metabolism, and arginine biosynthesis pathways. The metabolism and biosynthesis of starch, sucrose, tyrosine, galactose metabolism, and aminoacyl-tRNA biosynthesis were significantly upregulated by adding the combination of Zhang and M8. This work provides a detailed insight into different effects of Zhang and M8 used alone or in combination on the volatile and nonvolatile metabolomic profiles of yogurts.