Chitosan immobilized novel peroxidase from Azadirachta indica: Characterization and application

In the present paper, a peroxidase was purified from the leaves of a medicinal tree, namely Azadirachta indica, to 45.2 folds with overall recovery of 61%. Based on the subunit size, the purified peroxidase was suggested to be a monomeric structure of size 50kDa and exhibited good thermostability as it was fully stable at 65°C for 1hr and also retained about 73% activity at 70°C till 30min. The substrate affinity was found to be in order of guaiacol>pyrogallol>o-dianisidine. The purified peroxidase was found to be insensitive towards high concentrations of Na⁺, Ca²⁺, Mg²⁺ and Mn²⁺. Heavy metals, namely Cs²⁺, Co²⁺ and Cd²⁺ activated the peroxidase while that of Hg²⁺ deactivated the peroxidase in concentration dependent manner. The purified peroxidase exhibited tolerance towards organic solvents in order of ethanol>butanol>isopropanol>acetone. Immobilization of purified peroxidase by entrapment into chitosan beads led to shift in its optimum pH from pH 5 to 7 and considerable enhancement in dye decolorization ability as compared to that of free enzyme. Thus, based on all the above properties, it may be suggested that the purified A. indica peroxidase is a promising candidate for industrial applications.