Characterisation of Bacteriocins Produced by Lactobacillus spp. Isolated from the Traditional Pakistani Yoghurt and Their Antimicrobial Activity against Common Foodborne Pathogens

Abstract

Lactic acid bacteria (LAB) are widely known for their probiotic activities for centuries. These bacteria synthesise some secretory proteinaceous toxins, bacteriocins, which help destroy similar or interrelated bacterial strains. This study was aimed at characterising bacteriocins extracted from Lactobacillus spp. found in yoghurt and assessing their bactericidal effect on foodborne bacteria. Twelve isolated Lactobacillus spp. were examined to produce bacteriocins by the organic solvent extraction method. Bacteriocins produced by two of these strains, Lactobacillus helveticus (BLh) and Lactobacillus plantarum (BLp), showed the most significant antimicrobial activity, especially against Staphylococcus aureus and Acinetobacter baumannii. Analysis of SDS-PAGE showed that L. plantarum and L. helveticus bacteriocins have a molecular weight of ~10 kDa and ~15 kDa, respectively. L. plantarum (BLp) bacteriocin was heat stable while L. helveticus (BLh) bacteriocin was heat labile. Both bacteriocins have shown activity at acidic pH. Exposure to a UV light enhances the activity of the BLh; however, it had negligible effects on the BLp. Different proteolytic enzymes confirmed the proteinaceous nature of both the bacteriocins. From this study, it was concluded that bacteriocin extracts from L. helveticus (BLh) can be considered a preferable candidate against foodborne pathogens as compared to L. plantarum (BLp). These partially purified bacteriocins should be further processed to attain purified product that could be useful for food spoilage and preservation purposes.

Purification and characterization of bacteriocins-like inhibitory substances from food isolated Enterococcus faecalis OS13 with activity against nosocomial enterococci

“…There are previous reports of many BLIS becoming less heat-stable during subsequent purification steps 55,56 . The larger size of enterocin OS13α and OS13β being 8079.1 Da and 7858.6 Da, respectively, could interpret the reasons behind their heat sensitivity 39,57,58 . Although the crude BLIS with an initial activity of 10,240 AU/mL was decreased to be 1,280 AU/mL (12.5%) after proteinase K treatment but the purified enterocin OS13α was sensitive to proteinase K (50% reduction in its activity), which strongly suggests its proteinaceous nature 52,59 .…”

Probiotic Properties of Lactobacillus helveticus and Lactobacillus plantarum Isolated from Traditional Pakistani Yoghurt

“…The included species used in this study are Acinetobacter baumanni , Bacillus subtilis , Enterococcus faecium DO, Escherichia coli , Klebsiella pneumoniae , Methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa , Salmonella paratyphi A , Staphylococcus aureus , and Streptococcus pyogenes. The same bacterial isolates were used in a previous study by Hassan et al [ 29 ].…”

“…The bacteriocin-producing isolates were obtained from screening 50 traditional Pakistani yoghurt samples used in the previous study conducted by Hassan et al [ 29 ].…”

“…In our previous study [ 29 ], we isolated bacteriocin from two lactobacilli, L. plantarum and L. helveticus , which effectively inhibited foodborne pathogens. In this study, we extended our research and evaluated the probiotic potential of bacteriocin-producing species, as very few bacteriocin producing probiotic species were described earlier.…”

Probiogenomics Analysis of 97 Lactobacillus crispatus Strains as a Tool for the Identification of Promising Next-Generation Probiotics

“…Among the dominant bacterial genera observed in the vaginal microbiota, the most prevalent are LAB bacteria, particularly the genus Lactobacillus , represented by the species Lactobacillus iners , Lactobacillus crispatus , Lactobacillus jensenii, and Lactobacillus gasseri [ 4 ]. Interestingly, in addition to the release of lactic acid and the acidification of the surrounding environment, these species have been shown to produce bacteriocins that counteract colonization of opportunistic pathogens [ 5 ].…”