Poly(acrylamide/vinylsulfonic acid) hydrogel for invertase immobilization

Poly (acrylamide/vinylsulfonic acid) PA/VSA and poly (acrylamide) PA hydrogels were prepared by free radical polymerization in the presence of a crosslinker, to be used as a support for the invertase enzyme. Spectrophotometric, thermal analysis methods, swelling, and diffusion experiments were used for the characterization of hydrogels. SEM images show that the hydrogels have a smooth, homogeneous, highly porous and spongy morphology. The swelling of PA/VSA was higher than that of PA in water. The diffusion of water within the hydrogel was found to be non-Fickian. Invertase was immobilized onto PA and PA/VSA (immobilized invertases named PA-I and PA/VSA-I, respectively). The optimum pH values were found to be; 5.0, 3.0, and 3.0 for free invertase, PA-I, and PA/VSA-I, respectively. The optimum temperature values were 40°C, 50°C, and 60°C for free invertase, PA-I and PA/VSA-I respectively. Michaelis Constant, K_m ; for free invertase and PA-I and PA/VSA-I were found to be 11.80, 21.40, and 18.42 mM, respectively. Maximum reaction rate; V_max value for free invertase and PA-I and PA/VSA-I were found to be 7.46 μmol min^-1 , 5.91 μmol min^-1 , and 6.35 μmol min^-1 , respectively. PA/VSA-I showed excellent thermal, operational, storage, and pH stability.