A novel peptide derived from casein hydrolysates as a growth factor for Lactobacillus delbrueckii subsp. bulgaricus sp1.1

Notably, oligopeptides may serve as the primary nitrogen source, has the potential of enhancing the resistance of microbial strains to acidic environments. In this study, the impact of various casein hydrolysates on the proliferation of L. delbrueckii subsp.bulgaricus sp1.1 and the composition of peptides were studied. This study unveiled a novel peptide, KEGIHAQ, with a significant capacity to enhance both acid tolerance and proliferation of LAB. Transcriptomic analysis revealed that KEGIHAQ may be transported into cells through oppA/dppA transporters to reduce the ATP demand in the process of amino acid transport, and then it was hydrolyzed by endopeptidases such as pepO and aminopeptidases such as pepC to generate amino acids, which further enhanced the growth activity and acid tolerance of bacteria by regulating amino acid metabolism and synthesis pathways, carbohydrate metabolism, purine and pyrimidine synthesis metabolism, DNA replication and RNA modification, and the synthesis of cell membrane and cell wall components. These results provided valuable insights in identifying target peptides for nitrogen sources in future LAB high-density cultures, whether through biosynthesis or chemical synthesis.