Antibacterial Mechanism Oi Lactobacillus Salivarius Zdy159a And Development Of Synbiotics Microcapsule

Lactobacillus salivarius could inhibit the growth of pathogens, prevent oral and gastrointestinal disease, its survival was affected by environmental factors. For development of probiotics, investigation of antibacterial mechanism and improvement of survival rate of L.salivarius in adverse environment is significance.In this study, factors affecting antibacterial activity of L. salivarius ZDY159 a were studied by employing co-culture and Oxford cup method, using Escherichia coli O157:H7 NCTC12900 and Staphylococcus aureus CMCC26003 as indicator strains.The viable cell counts of L.salivarius ZDY159 a were improved by internal/external gelation with optimal encapsulation parameters. Moreover, simulated gastric juice and bile salt tolerance of microcapsules of L.salivarius ZDY159 a was studied, and its storage period was predicted.Results showed L. salivarius ZDY159 a had strong inhibitory effect on two indicator strains, its antibacterial activity was attributed to organic acids, bacteriocin(proteins or peptides) and hydrogen peroxide yielded in the fermentation. 10%(m/v)glucose solution provided the best protective effect for L. salivarius ZDY159 a. The cell counts of L. salivarius ZDY159 a was the highest, using 2%(m/v)galacto-oligosaccharide as carbon source. By optimizing the microencapsulating parameters, combination of 2%(m/v) sodium alginate and 2%(m/v) CaCl2 was used for external gelation encapsulation, and that of 1%(m/v) sodium alginate and 0.5%(m/v) CaCO3 for internal gelation encapsulation.Compared to free cells of L. salivarius ZDY159 a, the survival rate of L.salivarius ZDY159 a in internal and external gelation microcapsules, which were challenged by 0.3% bile salt, increased by 1000 and 38 fold, respectively, and that treated by simulated gastric juice increase also. The simulated gastric juice and bile salt tolerance of internal gelation microcapsules was stronger than that of external gelation microcapsules. The storage period of internal and external gelation microcapsules was 29 and 42 weeks, respectively.In conclusion, the tolerance in bile salt and simulated gastric juice of L.salivarius ZDY159 a was improved by internal and external gelation, and external gelation of L. salivarius ZDY159 a prolonged the storage period of cell counts.