Investigation of bacteriocin properties produced by Lactobacillus helveticus and evaluation of its antimicrobial activity on pathogenic microorganisms

Bacteriocins are generally defined as peptides or proteins ribosomal synthesized by bacteria that inhibit or kill other microorganisms. Nowadays, bacteriocin industry as natural preservatives have substantially grown replacing the role of chemical preservatives in enhancing shelf-life and safety of food. The progress in bacteriocin study has been supported by the emerging of consumer demand on the applications of natural food preservatives. In this study, Lactobacillus helveticus were identified using the 16S rRNA gene sequencing method. The antimicrobial activity of the neutralized supernatant of Lactobacillus helveticus against some pathogenic microorganisms was investigated. Then, the different properties of this bacteriocin compound, such as its protein nature, heat and pH resistance, as well as the storage temperature on its stability, were examined. In this study, the supernatant of L. helveticus, showed antimicrobial activity against 7 pathogenic bacteria with 8.5-18.7 mm diameter in inhibition zone. The bacteriocin produced by L. helveticus was completely sensitive to proteinase K, α-chymotrypsin, protease, and trypsin; however, after exposure to pepsin, the activity was reduced by about 41% for Staphylococcus aureus and about 30% for Micrococcus luteus. Supernatants containing bacteriocin were resistant to different temperatures as well as pHs 2 to 11. Also, the best temperature for storing the studied bacteriocin was -80 oC for 1 month. The ability of bacteriocin produced by L. helveticus to inhibit growth of various pathogens as well as high stability to pH and temperature can be introduced it as a natural preservative.