Application of Bacillus licheniformis probiotic vesicles as a natural antibacterial to improve the quality and safety of rainbow trout fillets

Bacteria release membrane vesicles into the extracellular environment but their activity is unknown. In this study, the use of extracellular vesicles isolated from the probiotic Bacillus licheniformis to protect rainbow trout fillets against spoilage and reduce of fillet quality was investigated. The probiotic B. licheniformis was isolated from edible fish. Probiotic vesicles were also made using the ultracentrifuge protocol. There was a significant difference in the size of probiotic-derived vesicles after 8, 24 and 48 hours of incubation. The results showed that after incubation until 16 hours, the number of cells increased to 8.09 10 108 CFU / ml. The pH reduced and reached to 4.002 at 24:00, which was the best incubation time for the bacterial growth. The vesicles derived from the probiotic B. licheniformis were collected and exposed to Shewanella putrefaciens at a concentration of 1011-107 vesicles per ml to confirm the antibacterial activity at 1011-10 vesicles per ml. Ml, with 44.34% had the highest inhibitory power of bacterial growth. Finally, rainbow trout stored at 4 ° C after covering with vesicles derived from probiotics and 0.5% sodium erythorbate were stored for 5 days, followed by red markers and Fillet quality indicators were examined. The results showed that the freshness and quality indicators of fish including peroxide, TVBN, total count of fillet bacteria and thiobarbituric acid in the group receiving probiotic-derived vesicles were lower than control group and the low-dose vesicle-derived group. Of probiotics. According to the results of this study, membrane vesicles isolated from the probiotic B. licheniformis have the potential for use in the food and storage industries while maintaining the appearance of fillets, and this new substance is a beneficial antibacterial agent for a long time and increase the longevity of fish fillets.