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Purification and Characterization of �?²-galactosidase from Kluveromyces lactis Isolated from a Yoghurt Waste Site

Tolulope T Oluwaniyi, Bridget O Omafuvbe, Femi K. Agboola

Some properties of β-galactosidase extracted and purified from Kluyveromyces lactis isolated from a yoghurt waste site were investigated. The crude β-galactosidase isolated from Kluyveromyces lactis was purified by ammonium sulphate precipitation and DEAE-Sephadex ion exchange chromatography. Specific activity of the partially purified enzyme was 107.50 μmole/min/mg of protein and a 7% yield. The molecular weight of the enzyme was 199 kDa as determined by gel filtration on Bio-gel P-200. The Michealis-Menten constant (Km) and maximum velocity (Vmax) value obtained was 3.56 ± 0.62 mM and 0.61 ± 0.08 μmole/min/ml for the enzyme with ortho-nitrophenyl-β-D-galactopyranoside (oNPG) substrate while the Km and Vmax was 18.01 ± 0.23 mM and 0.15 ± 0.04 mmol/20 min/L with lactose substrate. The optimum pH of purified enzyme was 7.5 and 6.5 with oNPG and lactose substrate respectively. The optimum temperature was 40°C with both substrates. This β-galactosidase may have applications in the conversion of whey a by-product of dairy industries into useful products.