The inhibition mechanism of ε-Polylysine against Bacillus cereus emerging in surimi gel during refrigerated storage.

BACKGROUND Refrigeration is commonly used in the processing and storage of surimi products. However, refrigerated surimi products are susceptible to microbial contamination, which leads to deterioration of the products and shortens their shelf life. The aims of the present study were therefore to evaluate the effects of epsilon-polylysine (epsilon-PL) on spoilage bacteria in surimi products, and to investigate the antibacterial mechanism of Bacillus cereus, which is the dominant spoilage bacterium. RESULTS epsilon-Polylysine with a high degree of polymerization (20-30K) proved able to decrease the total number of colonies in surimi products and showed an obvious antibacterial effect against B. cereus. After epsilon-PL treatments, the distinct broken areas on the bacterial surfaces and the aggregations of cells were observed by scanning electron microscope (SEM). The intracellular materials, such as small molecules, soluble proteins, and deoxyribonucleic acids in the cells were analyzed, which revealed the destructive effects of epsilon-PL on bacterial cells. Experiments with propidium iodide (PI) infiltration experiments verified that the permeability of cell membranes was enhanced by epsilon-PL treatment. CONCLUSION These results indicated that epsilon-PL could destroy the cell membranes and change the permeability of B. cereus, and subsequently the cell contents leaked out to achieve antibacterial effects. (c) 2018 Society of Chemical Industry