Comparative analysis of untargeted metabolites in fermented camel and bovine milk using UPLC-MS/MS metabolomics

This untargeted UPLC-MS/MS study investigates the differences among Lactobacillus helveticus, L. delbrueckii subsp. bulgaricus, and Streptococcus salivarius subsp. thermophilus in the fermentation of camel milk (CM) and bovine milk (BM). 13,400 metabolites were detected, of which 3,632 compounds were identified. L. helveticus was distinctly different from the other two bacteria in both the number and type of metabolites, as shown by principal component analysis, heat map, and UpSet plot. A diverse array of metabolites associated with amino acid metabolism, such as tyramine, citrulline, ornithine, γ-aminobutyric acid, and phenylpyruvic acid, along with the prebiotic carbohydrate raffinose, bioactive lipids (including γ-linolenic acid, docosapentaenoic acid, and 16-hydroxyhexadecanoic acid), niacin, and the nucleotides hypoxanthine and guanine, were higher in CM compared to BM, especially when fermented with L. helveticus. In contrast, the hypertensive marker angiotensin-(5–8) and D-serine were lower in CM than BM fermented with L. helveticus. These findings suggest that the fermentation of CM with L. helveticus, whether alone or in combination with L. bulgaricus and S. thermophilus, leads to metabolic alterations that may affect the nutritional properties of the final product.