Rapid Spectrophotometric Determination of Hypothermia Protection Activity of Sericin Peptides on Lactobacillus bulgaricus

Sericin peptides have a high proportion of hydrophilic amino acid residues, which are considered to protect cells from freezing stress due to the maintenance of water in the cells. In this paper, the hypothermia protection effect of sericin peptides was studied by reading optical density of cells at 600 nm, which was detailedly optimized to be a direct and practical spectrophotometric method. The survival rate of Lactobacillus bulgaricus after frozen storaged with addition of 0.1 mg/mL sericin peptides was close to that of 10% (v/v) glycerol (p > 0.05). The survival rate of 5 mg/mL sericin peptides was up to 64.17%.