A novel killer protein from Pichia kluyveri isolated from an Algerian soil: purification and characterization of its in vitro activity against food and beverage spoilage yeasts

A novel killer protein (Pkkp) secreted by a Pichia kluyveri strain isolated from an Algerian soil was active against food and beverage spoilage yeasts of the genera Dekkera , Kluyveromyces , Pichia , Saccharomyces , Torulaspora , Wickerhamomyces and Zygosaccharomyces . After purification by gel filtration chromatography Pkkp revealed an apparent molecular mass of 54 kDa with SDS-PAGE. Minimum inhibitory concentrations (MICs) of purified Pkkp exhibited a high in vitro activity against Dekkera bruxellensis (MICs from 64,000- to 256,000-fold lower than that exhibited by potassium metabisulphite) and Saccharomyces cerevisiae (MICs from 32,000- to 64,000- fold lower than potassium sorbate). No in vitro synergistic interactions (calculated by FIC index − Σ FIC) were observed when Pkkp was used in combination with potassium metabisulphite, potassium sorbate, or ethanol. Pkkp exhibited a dose–response effect against D. bruxellensis and S. cerevisiae in a low-alcoholic drink and fruit juice, respectively. The results of the present study suggest that Pkkp could be proposed as a novel food-grade compound useful for the control of food and beverage spoilage yeasts.