Abstract
Probiotic yeast strains viz. Yarrowia lipolytica VIT-MN01, Kluyveromyces lactis VIT-MN02, Lipomyces starkeyi VIT-MN03, Saccharomycopsis fibuligera VIT-MN04 and Brettanomyces custersianus VIT-MN05 were investigated as producer of killer toxin. Among the five yeasts, three strains showed more killer toxin production. The maximum killer activity (12 aU/mg) against sensitive strain Saccharomyces cerevisiae was obtained at pH-3 with 0.5% NaCl at 25°C by using response surface methodology. The purified killer toxin K2 and K3 showed the highest killer activity against foodborne pathogens viz. Bacillus cereus, E. coli, Pseudomonas spp., Klebsiella spp. and Candida tropicalis. The purity of the killer toxin was confirmed by HPLC analysis. The molecular mass of killer toxin was 22 kDa (K2), 18 kDa (K3) and 14 kDa (K4). The results of the present study suggest that killer toxins produced by probiotic yeast strains can be used as an antimicrobial agent to control the microbial contamination in the food industry.
Highlights
Yeasts are capable of producing antimicrobial compounds that may inhibit the growth of harmful mold or bacteria (Younis et al, 2017)
Five probiotic yeast strains viz. Y. lipolytica Vellore Institute of Technology (VIT)-MN01, K. lactis VIT-MN02, L. starkeyi VIT-MN03, S. fibuligera VIT-MN04 and B. custersianus VIT-MN05 were investigated for their killer toxin production
Probiotic yeasts strains viz. Y. lipolytica VIT-MN01, K. lactis VIT-MN02, L. starkeyi VIT-MN03, S. fibuligera VIT-MN04 and B. custersianus VIT-MN05 were isolated from different sources and reported as potential probiotics (Ragavan and Das, 2017)
Summary
Yeasts are capable of producing antimicrobial compounds (killer toxins) that may inhibit the growth of harmful mold or bacteria (Younis et al, 2017). Killer yeast and their toxins are having environmental, technological and medical importance. Killer toxins may have potential applications in various industrial sectors such as food, pharmaceutical, agricultural and fermentation due to its antagonism activity against pathogens (Lopes and Sangorrin, 2010; Chi et al, 2010). Five probiotic yeast strains viz. Y_lipolytica VIT-MN01, K. lactis VIT-MN02, L. starkeyi VIT-MN03, S. fibuligera VIT-MN04 and B. custersianus VIT-MN05 were investigated for their killer toxin production. The purified killer toxin was tested for antimicrobial activity against foodborne pathogens viz. Bacillus cereus, E. coli, Pseudomonas spp. and Klebsiella spp. and Candida tropicalis. The purity and molecular weight of killer toxin was assessed by HPLC and SDS-PAGE, respectively
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