Adsorption and hydrolytic activity of trypsin on a carboxylate-functionalized cation exchanger prepared from nanocellulose.

Immobilization of enzymes on polymer supports has been considered as a powerful technique in biomedical applications. In this study, a cellulose-based hydrogel, poly(acrylic acid)-modified poly(glycidylmethacrylate)-grafted nanocellulose (PAPGNC) was synthesized by graft copolymerization technique and well characterized. A pancreatic serine protease trypsin (TRY) was immobilized onto PAPGNC, under different optimized conditions. The optimum pH for TRY adsorption was found to be 6.5, and the adsorption attained equilibrium within 90 min. The kinetic data were found to follow pseudo-first-order model, which is based on solid capacity. The well agreement of equilibrium data with Langmuir isotherm model confirms the monolayer coverage of TRY onto PAPGNC surface, and the maximum adsorption capacity was found to be 140.65 mg/g at 30 °C. The temperature dependence indicates an endothermic process. The relative activity of immobilized TRY in the hydrolysis of casein was higher than that of the free enzyme over broader temperature ranges. The immobilized TRY had high temperature and long-storage stability as compared to free TRY. Spent adsorbent was effectively degenerated using 0.1 M KSCN with the retention in catalytic activity of 87% even after four cycles. The present investigation shows that PAPGNC is a valuable polymer support for the recovery of TRY from aqueous solutions and subsequent casein hydrolysis.