Characterization of antibacterial activity of a N-acetylmuramoyl-L-alanine amidase produced by Latilactobacillus sakei isolated from salami.

Lactic acid bacteria are the predominant group within meat products, whose metabolites such as bacteriocins and peptidoglycan hydrolases inhibit pathogenic or spoilage bacteria. Fermented meat products, as a salami, is a good source to analyze the viable microbiota, due to these products present a low risk to consumer health. The aim of this work was to identify the lactic acid bacteria with broad antibacterial activity present in salami, purify the protein responsible for this activity, achieve antagonistic spectrum and perform the biochemical characterization. Five strains from salami were selected, isolated and identified by 16S rRNA gene sequencing. The antimicrobial activity was evaluated by antagonism assay and zymography, using spoilage microorganisms commonly found in meat products. The strain that showed a broad antibacterial activity was Latilactobacillus sakei and the antibacterial activity was given by a protein with 75-kDa of molecular mass, identified by LC/MALDI-TOF/TOF. The sequence analysis showed 67% of identity with a N-acetylmuramoyl-L-alanine amidase protein with five non-identical LysM domains. The purified protein showed an optimal pH of 8.0 and heat resistance at 80 °C for 10 min. L. sakei strain displayed antibacterial activity against Gram-negative and Gram-positive spoilage microorganisms. The results of this study provide the information to use Latilactobacillus sakei as a starter culture which will provide the necessary metabolites to combat undesirable microorganisms. Additionally, the conditions and properties for the best application and use of the antibacterial protein produced by this strain. This protein may have a potential use in the food industry as a new antibacterial agent.