Characterization of soybean peroxidase for the treatment of phenolic wastewaters

Soybean peroxidase (SBP) was investigated as an alternative to horseradish peroxidase (HRP) in the catalytic removal of phenolic compounds from wastewaters. The catalytic activity of SBP depended on reaction pH and hydrogen peroxide concentration. A pseudo steady state kinetic model describing the dependence of activity on peroxide concentration was derived and apparent kinetic constants describing the oxidation of SBP by hydrogen peroxide and the reduction of SBP by phenol were determined. SBP incubated at 25$ sp circ$C was relatively stable in neutral and alkaline buffer but was inactivated in acidic buffer. SBP incubated at elevated temperatures experienced 1st order thermal inactivation that depended on incubation temperature and pH. At 25$ sp circ$C in pH 7.4 buffer, SBP incubated with hydrogen peroxide demonstrated biphasic suicide inactivation whose rate depended on the initial peroxide concentration. SBP catalyzed removal of seven phenolic compounds from aqueous solution depended on enzyme dose, reaction pH and buffer species, the phenolic compound, and the measurement technique used to quantify removals. While the observed ability of SBP to catalyze phenolic compound removal was less efficient than the reported ability of HRP, the industrial grade cost of SBP is sufficiently less than the cost of HRP that SBP can be considered an attractive alternative to HRP in the treatment of wastewaters containing phenolic compounds