Caracteriza？？o cinética e termodinamica de β-galactosidase de Kluyveromyces marxianus CCT 7082 fracionada com sulfato de am？nio

β-galactosidase is an important enzyme that acts on lactose hydrolysis and can be used to obtain food for consumers intolerant to this disaccharide. the yeast kluyveromyces marxianus presents a good growth yield, is a safe microorganism for industrial applications and has been used for enzyme production using the submerged process. the β-galactosidase obtained was fractionated with ammonium sulphate and characterized with respect to its optimum temperature and ph, thermal stability and its d and z values, as well as its kinetic and thermodynamic parameters. the optimum temperature and ph were 45-50 °c and 7.0, respectively. the activation energy and the deactivation reaction of the enzymatic reaction were, respectively, 9.8 kcal.mol-1 and 64.2 kcal.mol-1. the km and vmax values obtained were 3.7 mm and 99.0 u.ml-1, respectively. the gibbs free energy decreased with increasing temperature and the enzyme was more stable at 30 °c (？g* = 106.8 kj.mol-1). the enthalpy was 313.04 kj.mol-1 and entropy 0.68 kj.mol.k-1. the d value confirmed that the enzyme was more stable at temperatures around 30 °c (d = 11,513.0 min) and the z value was 5.8 °c.