Abstract
Lactobacilli, as the largest group of lactic acid bacteria, produce large amounts of antimicrobial metabolites such as organic acids, fatty acids, ammonia, hydrogen peroxide, diacetyl and bacteriocin, which inhibit the growth of pathogenic bacteria and increase shelf life of food. The aim of this study was to identify the Lactobacillus spp. isolated from Iranian raw milk Motal cheese and to detect the presence of bacteriocin genes in the isolated Lactobacillus strains exhibiting antimicrobial activity. For this purpose, 6 Motal cheese samples from Dasht-e-Moghan region, Iran, were subjected to microbial characterization. Nineteen Lactobacillus spp. were isolated and subsequently identified based on biochemical and molecular methods. According to the sequencing of isolates, Lactobacillus spp. consisted primarily of Lactobacillus brevis, Lactobacillus plantarum, Lactobacillus casei and Lactobacillus buchneri. The identified isolates were then evaluated for antimicrobial activity against Escherichia coli ATCC 25922, Listeria innocua ATCC 33090 and Staphylococcus aureus ATCC 25923. The results of PCR analysis using specific primers of genes encoding Bacteriocin, revealed the presence of Plantaricin A and Plantaricin EF in all Lactobacillus plantarum isolates and Brevicin 174A in 5 of Lactobacillus brevis isolates, whereas the gene encoding Pediocin PA-1 was not observed in any of examined isolates. It is therefore concluded that bacteriocinogenic isolates could be recommended as suitable candidates to be used as starter, adjunct-starter or antimicrobial agents for production of fermented and non-fermented products.
Highlights
Conversion of carbohydrate to lactic acid by lactic acid bacteria (LAB) may be considered as the most important fermentation in food industry
Morphological and biochemical properties of Lactobacillus strains A total of 64 colonies grown on de Man (MRS) under aerobic and microaerophilic conditions at 37 °C were randomly isolated for further studies
This study provides an overall analysis on Lactobacillus strains communities in Motal cheese
Summary
Conversion of carbohydrate to lactic acid by lactic acid bacteria (LAB) may be considered as the most important fermentation in food industry. The characteristic aroma, flavor, and texture of fermented foods (e.g., dairy, meat, and vegetables) are often due to growth of these bacteria. Some strains of LAB isolated from dairy and other fermented products may contribute to the safety and quality of foods owing to possessing antimicrobial agents. Some strains of LAB play a vital role in the digestive tract by producing antimicrobial metabolites such as bacteriocins and prevent the growth of pathogenic and infection microorganisms (Castro et al 2011; Ghanbari et al 2013; Parada et al 2007; Ahmed et al 2013; Mahrous et al 2013). Bacteriocins are divided into two main classes, lantibiotic such as Nisin (class I), and nonlantibiotic such as Pediocin and PlantaricinEF (class II) (Noda et al 2015)
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