PRODUCTION AND PARTIAL PURIFICATION OF BETA-GALACTOSIDASE PRODUCED BY CANDIDA TROPICALIS ISOLATED FROM DAIRY EFFLUENT

Résumé

Beta-galactosidase (-D-galactoside galactohydrolyse; E.C. 3.2.1.23), in other words lactase, is a commercially important enzyme that catalyzes the hydrolysis of lactose into its constituent monosaccharides glucose and galactose. It is widely distributed in nature, found in numerous plants, animals and microorganisms including yeast, fungi and bacteria. Hence, the study was designed to isolate, identify, optimization of production conditions for maximal production of β-galactosidase, extraction and partial purification of the enzyme. The proximate composition of the dairy effluent were determined using AOAC methods and it revealed; moisture (80%), ash (0.160%), crude fat (5.57%), crude protein (0.88%) and Carbohydrate (13.21%). The isolated yeast

strains were found to metabolize and ferment various mono and disaccharides which includes glucose, maltose, lactose, sucrose, and raffinose. Analytical Profile Index kit (API) was further used to confirm the yeast isolates Candida tropicalis. The activity of the enzyme was higher after 48 hrs fermentation period (0.089U/mL) during optimization. The enzyme displayed maximal activity around neutral pH of 6.0 (0.075U/mL) and at the temperature of 30°C (0.076U/mL). The Beta galactosidase was partially purified through Ammonium sulphate precipitation (75% saturation), Gel filtration and Ion exchange chromatography. The yield obtained after purification was (89.1%) with purification fold of (1.14) and specific activity of (0.224U/mg). Therefore, dairy effluent could serve as a cheap and efficient substrate for large scale production of Beta-galactosidase.