Study on separation and identification of a broad spectrum of bacteria producing lactic acid bacteria strains and characterization of its bacteriocin

Objective :To obtain a broad spectrum of bacteriocin-producing lactic acid bacteria strains from breastfeeding baby stool, researching and analyzing its physicochemical and biological properties of bacteriocins,predict its potential applications in the food industry. Methods:The antimicrobial activity of 23 Lactobacillus strains isolated from breastfeeding infant faeces was tested by the oxford cup agar diffusion method using Listeria monocytogenes and E. coli as indicator bacteria. The strains were identified by cell morphological,physiological,biochemical characteristics and 16 S r DNA sequence analysis,and from the acid,heat,protease sensitivity,antibacterial spectrum angles,analyze the biological characteristics of bacteriocins.Results:A broad spectrum bacteriocin producing strains BL-1 was isolated in this study. And results showed its bacteriocins have strong thermal stability and acid tolerance. Under the conditions of pH of 2,121℃,the bacteriocin activity remained stable and the pepsin could be completely decomposed it. And this bacteriocin showed the higher security and broad spectrum antimicrobial,the inhibitory effect was very obvious against Listeria monocytogenes,Staphylococcus aureus and other Gram-positive and negative bacteria such as Escherichia coli. Finally,it was identified as Lactobacillus rhamnosus. Conclusion:In this study,we isolated a broad spectrum bacteriocin producing Lactobacillus rhamnosus BL-1,and we found that its bacteriocin had excellent biological characteristics and great application prospects on the development of natural biological preservatives.