Production and biochemical characterization of Pleurotus ostreatus NRC 620 laccase and evaluation of its efficacy in apple juice clarification

The highest activity of the Pleurotus ostreatus NRC620 laccase enzyme occurred in the broth of mushroom growth after 25 days of incubation at 28 degrees C and static conditions. The optimum pH and temperature of the enzyme activity were revealed at pH 3.0, and 70 degrees C, respectively, and retained 68.33 and 59.61% of its activity after incubation at 40 and 50 degrees C for 2 h, respectively. The enzyme retained 100% activity after 2 h of incubation in citrate-phosphate buffer (pH 7.0). The addition of MgSO4 and CuSO4 with concentrations of 10 mM caused about 21% and 35% increase in enzyme activity, while NaCl, MnCl2, KCl, and CaCl2 inhibited the enzyme. The values of the kinetic parameters (Km and Vmax) of the Pleurotus ostreatus NRC 620 laccase were 1.99 mM and 16,217 mu mol Min-1 L-1 respectively, using ABTS as a substrate. The apple juice enzyme-treated sample showed a significant reduction in pH, as well as viscosity, after enzyme treatment along with storage time. Apple juice treatment with laccase exhibited slight degradation in total phenolic; however, this observation was not found in antioxidant activity.