Extraction, Purification and Thermodynamic Characterization of Almond (Amygdalus communis) b-Galactosidase for the Preparation of Delactosed Milk

Buffer type, pH and ionic strength, as well as the fraction of polyvinylpyrrolidone were optimized for efficient extraction of b-galactosidase from almond seeds. The enzyme was purified up to electrophoretic homogeneity employing (NH4)2SO4 (15–60 %) fractionation, size exclusion and ion-exchange chromatography. Molecular mass of b-galactosidase as estimated by gel filtration and SDS-PAGE was approx. 62 kDa, confirming its monomeric nature. The optimum activity of the enzyme was at pH=5.5, and it was stable within the range of pH=5.0–6.0. Various kinetic parameters of b-galactosidase thermal inactivation were calculated: DH°, DS° and DG° suggested that the enzyme undergoes significant processes of unfolding during denaturation. Using b-galactosidase from almond seed powder, lactose hydrolysis in milk up to approx. 50 % was observed. The findings indicate the potential use of almond seeds for the production of low/delactosed milk for lactose-intolerant population.