An immobilized invertase enzyme for the selective determination of sucrose in fruit juices
Orhun Hakkoymaz, Hidayet Mazi
Department of Chemistry, Gaziantep University, Faculty of Arts and Sciences, Gaziantep, 27310, Turkey.
Poly(N-vinylpyrrolidone-co-butylacrylate-co-N-hydroxymethylacrylamide) has been synthesized by free radical polymerization at 70°C. Copolymer were characterized by FT-IR, elemental analysis and viscometric methods. Invertase was immobilized onto poly(N-vinyl pyrrolidone-co-butyl acrylate-co-N-hydroxymethyl acrylamide) by entrapment method. Optimum parameters (pH, temperature, substrate concentration, amount of polymer) for immobilization to obtain maximum activity were investigated. Kinetic parameters, Km and Vmax, of the free and immobilized invertases were also assayed. Results showed that immobilization enhanced the enzyme stability against changes of pH and temperature and immobilized enzyme showed lower Km value than free enzyme. One of the most interesting results is that the optimum operational temperature of the immobilized enzyme was 15°C higher than that of the free enzyme. The next is the activity of the immobilized enzyme at the optimum temperature (70°C) was approximately the same as the activity of the free enzyme at its optimum temperature (55°C). Finally, immobilized invertase were used for determination of sucrose in commercial fruit juices. A new method and equation based on immobilized invertase were derived for determination of sucrose in commercial cheryy and pomegranate juices.
Keywords: Enzyme, Invertase, Immobilization, Sucrose, Method, Juice.