Abstract:
In this research, the immobilization of horseradish peroxidase into the chitosan incorporated silver nanoparticles with entrapment method was studied. The focus was given on the study of effects of horseradish peroxidase, chitosan, and silver nanoparticles concentrations on efficiency of immobilized enzyme based on reaction rate, maintenance and storage stability. In this study, the experiment was divided into two parts. First , the effect of pH of chitosan solution (4, 5 and 6), size of chitosan film (delicately cut, 0.3 x 0.3 and 0.5 x 0.5 cm2 ), and substrate concentrations (pyrogallol, 0.03 - 0.10 M and hydrogenperoxide, 0.10 - 0.60 M) were studied . The optimum conditions for enzyme activity were determined at pH 5 of chitosan solution, 0.5 x 0.5 cm2 of chitosan film size, 0.075 M pyrogallol, and 0.50 M hydrogenperoxide. Data from the first part were further applied to investigate with experimental design for optimum conditions of enzyme immobilization in chitosan incorporated silver nanoparticles. The silver nanopartilces , synthesized using reducing agents, had average size of 37 nm. The concentrations of enzyme solution (0.05, 0.10, and 0.15 mg/ml), chitosan solution (0.5, 1.0, and 1.5% w/v), and silver nanoparticles (0.4 x10-2, 0.8 x10-2, and 1.2 x10-2nM) were studied. The optimum conditions for enzyme reaction was found at 0.15 mg/ml of horseradish peroxidase, 0.5% w/v of chitosan, and 0.4 x10-2 nM of silver nanoparticles with the specific activity of 230 U/mg-enzyme. However, maintenance and storage stability of immobilized enzyme under this optimum conditions was quite low. The residue activity of immobilized enzyme was 21.38 % after 3 cycles of operation. After storing the immobilized enzyme at 4 ๐C and room temperature for 2 weeks, the residue activity were determined at 4.68 % and 6.44 %, respectively.