Kinetic studies of an amylase used commercially for the clarification of apple juice

Abstract

The effect of substrate and enzyme concentrations on the degradation of soluble corn starch with a commercial amylase (Rohalase HT) recommended for apple juice clarification was studied. The reaction was conducted at 50C at different pH values (3.6-5.6). Starch solutions containing from 2.48 to 14.85 mg/mL were used as substrate in the experiments. Influence of Ca2+ on amylase activity was also determined. Obtained results showed that amylase exhibits an optimal activity pH value of 4.6, following a Michaelis-Menten type kinetics (Km = 8.11 mg/mL and Vmax = 2.19 U/mg enzyme). The activity of amylase decreased significantly when CaCl2 was added to the amylase solution (final amylase concentration in reaction mixture: 5-10 mM). An empirical equation relating the rate of product of hydrolysis formation (dCm/dt) with starch (Cst) and amylase (Ce) concentrations was obtained: dCm/dt = 1.18 × Ce 0.77 × Cst 1.03 × [1-exp(-0.11 × t)].