Isolation, Identification and Antibacterial Characteristics of Lacticaseibacillus rhamnosus YT

Abstract

Pathogenic microorganisms have been detected in fermented food. Combining the enormous class of the pathogens and their continuously appearing mutants or novel species, it is important to select suitable and safe antibacterial agents for fermented food safety. Lactic acid bacteria (LAB) which produce diverse imperative antimicrobial metabolites have an immense number of applications in the food industry. Here, the human-derived strain YT was isolated due to its cell-free supernatant (CFS-YT) and cells (Cs-YT), respectively performed obvious inhibitory ring to Gram-positive and -negative spoilage bacteria. Strain YT was identified as Lacticaseibacillus rhamnosus by the 16s rDNA sequence and morphology. The antibacterial activity of CFS-YT was demonstrated to be growth-dependent, pHs-sensitive, broadly thermostable and enzyme-insensitive. Cs-YT displayed a broad antibacterial spectrum with the action mode of bacteriostasis. The antibacterial activity of Cs-YT was due to substances located at the cell surface which were sensitive to heat, stable at broad pH gradients and sensitive to specific enzymes. These data suggested that L. rhamnosus YT could be used as an alternative antimicrobial agent in fermented food biopreservation.