POTENTIAL APPLICATION OF AN ANTI‐AEROMONAS BACTERIOCIN OF LACTOCOCCUS LACTIS SSP. LACTIS IN THE PRESERVATION OF VEGETABLE SALAD

Abstract

AbstractThe potential use of bacteriocins as natural food preservative has a wide range of applications in food industry, but the range is restricted mostly up to gram‐positive microorganism. In our work, a Lactococcus lactis ssp. lactis HKT‐9 strain isolated from hukuti maas produced a bacteriocin active against a variety of gram‐positive as well as gram‐negative foodborne pathogens but specificity toward Aeromonas spp. Partially purified bacteriocin revealed that the peptide was thermoresistant (15 min at 121C), active at acidic to alkaline pH between pH 2.0 and 10.0. Its molecular weight was approximately 2.5 kDa and shared the properties of class II bacteriocin family. Furthermore, the gene cluster encoding for bacteriocin produced by L. lactis ssp. lactis HKT‐9 showed 100% homology with the operon encoding pediocin PA‐1(class IIa bacteriocin). Among detergents, sodium dodecyl sulfate, Tween 80 and Tween 20 enhanced bacteriocin activity. Enzymes like α‐amylase; DNase and RNase showed slightly increased bacteriocin activity. Its mode of action was bactericidal against Aeromonas hydrophila American type culture collection 7966. Addition of crude bacteriocin HKT‐9 at concentration of 100 μg/mL to artificially contaminated vegetables inhibited the growth of A. hydrophlia up to 7 log cfu/mL within 24 h for at least 10 days, whereas reduction of 6 log cfu/mL was observed for Staphylococcus aureus.Practical ApplicationBacteriocins are ribosomally synthesized polypeptides possessing bacteriocidal activity that are rapidly digested by proteases in the human digestive tract. They are a heterogenous group characteristically selected for evaluation and use as specific antagonists against problematic bacteria. With the emergence of antibiotic‐resistant pathogenic bacteria, the possibility of bacteriocins as supplements or replacements for antibiotics for therapeutic use is also being considered; however, their effectiveness in foods can become limited for various reasons, and cost remains an issue impeding broader use of bacteriocins as food additives. Of all the antimicrobial peptides, very few have been used as preservatives in the food industry and/or as antibiotic substances in medicine. In the present study, effectiveness of an anti‐aeromonas bacteriocin of Lactococcus lactis ssp. lactis was studied for the preservation of vegetable salad under in vitro conditions.