Antimicrobial activity of bacterial cell and cell free culture supernatant of Lactobacillus helveticus in-vitro and in a food model

In this study, the antimicrobial properties of bacterial cell and cell free culture supernatant of Lactobacillus helveticus was investigated both in vitro and in vivo (food). For this purpose, at first, cell free culture supernatant (CFS) was prepared from the mentioned Lactobacillus strain and then divided into three groups (control, treated by heat (100 °C for 15 min) and neutralized by NaOH). Antimicrobial activity of supernatant treated or no treated was investigated utilizing agar well diffusion and Disk diffusion method against two pathogenic bacteria including Salmonella enterica subsp. enterica and Staphylococcus aureus. Moreover, the antimicrobial activity of L. helveticus in cherry juice was evaluated during 24 h of incubation. The results showed that unheated and heated CFS were able to inhibit both pathogenic bacteria, but neutralized CFS had no antimicrobial activity. Inoculation of L. helveticus in cherry juice effectively (P <0.05) prevented the growth of Salmonella and Staphylococcus during the fermentation period. Therefore, based on the results, L. helveticus and its CFS can be used as an alternative to chemical preservative and as a natural antimicrobial source in the food industry.