Cryoprotective effect of antifreeze glycopeptide analogues obtained by nonenzymatic glycation on Streptococcus thermophilus and its possible action mechanism

This study aimed to investigate the cryoprotective activities of antifreeze glycopeptide analogues (GAPP) obtained by nonenzymatic glycation and explore the mechanism of GAPP on Streptococcus thermophilus during cold stress. Results showed that the survivability of S. thermophilus increased from 32.03% to 92.56% treated with 5 mg/mL GAPP. The glass transition temperature of GAPP increased from -27.6 to -21.4 degrees C after nonenzymatic glycation. The thermal hysteresis activity of GAPP was significantly higher and the amount of ice nuclei in GAPP groups was lower than that of BSA and antifreeze peptides. GAPP could significantly inhibit the leakage of intracellular proteins and nucleic acids, and prevent the decrease of beta-galactosidase and lactic dehydrogenase activities. Cells disruption and contents leakage could be observed in control groups, while cells with GAPP maintained satiation and integrity. The results suggested that GAPP could be potentially developed as a new and effective probiotics cryoprotectant in frozen food system.