Screening and Identification of an Antibacterial Agent-Producing Lactobacillus Strain and its Application in Bananas Preservation

With the development and progress of human society and the continuous enhancement of people's health awareness, lactic acid bacteria inhibitors as a natural biopreservative have an irreplaceable position, with the advantages of high efficiency, broad spectrum, stability, safety and other characteristics. This paper studied the antibacterial effect of 23 lactic acid bacteria; the strains with the best antibacterial effect was identified by 16S rDNA method as being Lactobacillus rhamnosus L57 and was applied to banana storage. Our study showed that Lactobacillus rhamnosus L57 has a broad spectrum, inhibiting Escherichia coli, Staphylococcus aureus, Vibrio alginolyticus and Bacillus nato. Excluding the interference of organic acids, hydrogen peroxide and extracellular polysaccharide, the salting out of ammonium sulfate preliminarily determined that the proteins or peptides are the antibacterial substances in the antibacterial agent. Physicochemical properties showed that the microorganism had good antibacterial activity after trypsin, pepsin and papain, with good tolerance to pH, temperature and UV light, and the pH optimal range of 2.0-4.0. The mixture of freeze-dried powder of L. rhamnosus L57, chitosan and natamycin was used for banana preservation, with the proportion of freeze-dried powder of 1.25%, chitosan 1.5% and natamycin 0.03%. The preservation period was extended by 4 days compared with the absence of either bacteriostatic agent.