Effective immobilization of lipase onto a porous gelatin-co-Poly(vinyl alcohol) copolymer and evaluation of its hydrolytic properties


Correspondence to: I. Kaur (E-mail: ij_kaur@hotmail.com)


Crosslinked copolymers of gelatin and poly(vinyl alcohol) (PVA) with excellent water absorption and water retention abilities were successfully synthesized using 60Co γ radiation. Ammonium persulfate (APS), as a water-soluble initiator and sodium bicarbonate (NaHCO3) as a foaming agent were used. The best synthesis conditions were evaluated with regard to the maximum percentage of swelling as a function of the APS concentration, NaHCO3 concentration, amount of water, and reaction time. The maximum swelling percentage (1694.59%) of the copolymer gelatin-co-PVA, was obtained at the optimum parameters [APS] = 2.92 × 10−1 mol/L, [NaHCO3] = 7.94 × 10−2 mol/L, and 1.5 mL of water with 31.104 kGy of the γ radiation dose. The copolymer was characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) methods. The SEM analysis showed a highly nanoporous and cellular structure of the copolymer. The copolymer was used as a support for lipase immobilization. The optimization of the reaction conditions, including the pH and temperature for immobilization, on the basis of the hydrolysis of p-nitrophenyl palmitate, was carried out. An excellent efficiency for protein loading (70%) at pH 8.5 by the copolymer was observed. The results observed during the evaluation of the hydrolytic properties showed excellent activity of the bound lipase. The porous gelatin-co-PVA bound lipase was found to be stable at 75°C and pH 8.5; it displayed 2.326 ± 0.005 U/g of lipase activity. The stability and activity of the copolymer-bound lipase were also studied as a function of the time at 75°C, and the biocatalyst was found to be stable and active up to 1 h, beyond which the activity decreased. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39622.