Isolation and Identification of Beta-galactosidase Producing Yeasts From Some Dairy Products

Document Type : Research articles.

Authors

1 Dairy Technology Research Department, Food and Technology Research Institute, Agriculture Research Center, Giza, Egypt

2 Agriculture Microbiology Department, Faculty of Agriculture, Fayoum University, Fayoum 63514, Egypt

3 Biochemistry Department, Faculty of Agriculture, Fayoum University, Fayoum 63514, Egypt

Abstract

Twenty-two β-galactosidase-producing yeast isolates were isolated from local dairy products. The purified isolates were evaluated for their β-galactosidase activity to identify the most productive isolates for subsequent investigations. The isolates were utilized in fermentation experiments, and β-galactosidase activity was assessed after 48 h. Fermentation experiments results indicated that isolates No. 1 and No. 13, which produced the highest enzymatic activity, were selected for studying the optimization of the environmental conditions for the enzyme production. Based on ITs rDNA gene sequence analysis, the two isolates were identified as Kluyveromyces lactis and Pichia kudriavzevii. The environmental factors for the maximum production of enzymatic activity, such as the pH of the medium, temperature, and incubation period were studied. The results demonstrated that the highest production of β-galactosidase under pH 5.0 being 188.12 nmol/ml/min for Kluyveromyces lactis and 174.07 nmol/ml/min for Pichia Kudriavzevii. The optimal environmental conditions for β-galactosidase production, such as pH, temperature, and incubation period, were, respectively, found to be 5 and 30 °C and 48 hours for both tested strains.

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