No abstract

Probiotic bacteria are finding newer and wider applications in the food and allied industries. They were increasingly used as biopreservatives. Seafood processing and packaging is emerging as a strong industry now a days. In this context, probiotic organisms having the capacity to inhibit the pathogens in seafood shall have immediate applications. Hence, we have made a study on exploring potential probiotic lactobacillus and their antagonistic mechanisms against sea food pathogens and few human pathogens. Thirty different bacterial strains were isolated from commercial and house hold curd samples from Chennai. They were found to be Lactobacillus spp. based on their microscopic and biochemical properties. They were tested for their antimicrobial potential against common sea food pathogens viz., Salmonella sp., Shigella sp. and Vibrio sp. and human pathogens such as Pseudomonas aeruginosa, Enterococcus faecalis and Staphylococcus aureus. While screening for bactericidal activity, out of thirty, a strain Lactobacillus sp. AMET2017 exhibited remarkable inhibitory activity against one seafood and one human pathogens (maximum of 14 mm zone of inhibition) followed by Lactobacillus sp. AMET2025 in comparison with the other strains against both sea food and human pathogens. Crude ethyl acetate extracts (EAE) and crude bacteriocin (CB) were separated from the broth culture of Lactobacillus sp. AMET2017 and their Inhibitory Concentration (IC50) was tested using MTT 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-Diphenyltetrazolium bromide) assay. It has been found that the comparatively the EAE had better performance and hence it alone subjected to further studies. The antibacterial mechanism of EAE from Lactobacillus sp. AMET2017 was analyzed. There has been no considerable change in protein synthesis but the DNA integrity was found to be affected in the tested pathogens. Hence, it is concluded that the EAE of Lactobacillus sp. AMET2017 inhibits the sea food and human pathogens by affecting their DNA integrity and thus they can be effectively characterized for the use as biopreservatives of sea foods.