CHEN Dawei, GUO Congcong, REN Chenyu, CHENG Yue, CHEN Chunmeng, QU Hengxian, WA Yunchao, YAN Xiantao, GUAN Chengran, ZHANG Chenchen, ZHENG Yingming, QIAN Jianya, GU Ruixia
Adhesion is the key for lactic acid bacteria (LAB) to play a probiotic role in the body, the research of the effect of freeze-dried protective agents on the adhesion of LAB will help to develop probiotic products and further explore their functions. The effects of the single protectant on the adhesion rate and survival rate of Lactobacillus plantarum 67 after vacuum freeze-drying were studied, and a single protective agent with better protection effect were selected, and the composite protective agent was optimized according to the adhesion rate and survival rate. The improvement effect of the optimized composite protective agent on the surface microscopic morphology, the ability to adhere to Caco-2 cells, and the ability to inhibit intestinal pathogens from adhering to Caco-2 cells of strain 67 after freeze-drying were explored. The results showed that the adhesion rate to Caco-2 cells of strain 67 was significantly decreased after freeze-drying in 5 kinds of composite protectors that removed skim milk (S), inulin (L), sucrose (C), sodium glutamate (G) and trehalose (T), respectively (P<0.05), and the survival rate was significantly decreased after freeze-drying in 3 kinds of composite protectors that removed L, G and sorbitol respectively (P<0.05). The adhesion rate of strain 67 to Caco-2 cells were greater than 5.85% after freeze-drying in 140 g/L S, 80 g/L L, 60 g/L C, 90 g/L G and 100 g/L T respectively, which significantly higher than other concentrations of their respective protective agents (P<0.05), and the survival rate were greater than 18.34% after freeze-drying in 120 g/L S, 100 g/L L, 100 g/L C, 70 g/L G and 80 g/L T respectively (P<0.05), which significantly higher than other concentrations of their respective protective agents. The adhesion rate and the survival rate of strain 67 were 28.73% and 93.52% respectively when the optimized composite protectant that contain 160 g/L S, 100 g/L L, 40 g/L C, 70 g/L G and 120 g/L T, and which significantly higher than not optimization that were 20.47% and 76.31% (P<0.05). Compared with the not optimization composite protectant, the change of cell morphology was smaller, and the strain 67 adhere to Caco-2 cells was more closely and without breaking, without collapsing, and the adhesin was surface proteins before and after freeze-drying. At the same time, the ability of strain 67 to inhibit the adhesion of Staphylococcus aureus and Escherichia coli to Caco-2 cells was significantly improved (P<0.05). S, L, C, G and T have a great impact on the adhesion rate and the survival rate of L. plantarum 67, and the optimized composite protective agent has a good protective effect on the adhesion ability, the survival ability and the ability to inhibit intestinal pathogenic bacteria from adhering to intestinal epithelial cells of L. plantarum 67 after freeze-drying.
