Safety evaluation, hydrolysis activity of Kluyveromyces marxianus JY-1 and its application to obtain immunomodulatory peptide from bovine casein

Except in vitro enzymolysis, there are few studies on the production of casein-derived immunomodulatory peptides by microbial fermentation technology. In this study, the ability of a strain of Kluyveromyces marxianus JY-1 isolated from traditional fermented milk in Xinjiang District (China) to release casein-derived immuno-modulatory peptides was evaluated. Results showed that this strain was safe and with high protease activity, which could highly hydrolyze casein. The hydrolysate of casein hydrolyzed by Kluyveromyces marxianus JY-1 could promote the proliferation of RAW264.7 macrophages and the production of cytokines (IL-6, IL-1 beta, and TNF-alpha) compared with the control group, showing obvious immunomodulatory activity. A nanoscale liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (Nano LC-Q-TOF-MS/MS) was used to determine the amino acid sequences of bioactive peptides in casein hydrolysate of Kluyveromyces marxianus. According to the structural characteristics of immunomodulatory peptides, 3 peptides (HPHPHLSF, PFPEVFG, and SPAQILQW) with immunomodulatory activity were selected from 55 identified peptides by using in silico methods. This study demonstrates that Kluyveromyces marxianus JY-1 has a wide range of potential applications in the production of immunomodulatory peptides from casein and other food proteins.