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.
Highlights
Foodborne diseases (FBDs) have been a global concern
The molecular size of bacteriocins extracted from Lactobacillus spp. was estimated by SDS-PAGE alongside molecular weight marker proteins
Bacteriocins extracted from Lactobacillus spp. had vigorous antimicrobial activity against Grampositive and Gram-negative pathogenic organisms, including S. aureus, methicillinresistant Staphylococcus aureus (MRSA), E. coli, Salmonella paratyphi, and Acinetobacter baumannii
Summary
Despite the use of modern food preservation techniques, the rate of food-related illness still increases and is a substantial cause of death, especially in countries where there is a lack of proper food safety monitoring systems. About onethird of the world population is suffering from food-related diseases each year due to the consumption of contaminated or intoxicated food like canned food, meat, poultry, and fermented dairy products [1]. Yoghurt is one of the widely used dairy products that has been traditionally made and used for centuries around the BioMed Research International globe (local name is Dahi in Pakistan). It is synthesised by milk fermentation with the help of bacteria. Many research studies have shown that yoghurt contains beneficial diversifying microflora, such as lactic acid bacteria (LAB) [3]
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