Integrated metabolomics and peptidomics to delineate characteristic metabolites in milk fermented with novel L3.

A novel wild-type () L3 with good fermentation characteristics and protein degradation capacity was isolated from raw milk samples. In this study, the metabolites in milk fermented with L3 were investigated by metabolomic and peptidomics analyses. The metabolomics results revealed that the metabolites in milk fermented with L3 were Thr-Pro, Val-Lys, l-creatine, pyridoxine, and muramic acid, which improved the taste and nutritional qualities of the milk. Moreover, the water-soluble peptides derived from L3 fermented milk exhibited high antioxidant properties and angiotensin I-converting enzyme inhibitory (ACEI) activities. Additionally, 152 peptides were found using liquid chromatography-mass spectrometry (LC-MS/MS). Furthermore, endogenous enzymes secreted by L3 cleaved - and -casein to release six ACEI peptides (ACEIPs), nineteen antioxidant peptides (AOPs), and five antimicrobial peptides (AMPS). Overall, these findings could be valuable in improving the quality of fermented milk.