New Poly(Acrylic Acid)-Based Functional Nanogels as Supports of Lipase: Evaluation of Hydrolytic Activity of the Immobilized Lipase

Background: Lipases are excellent biocatalysts with dual ability of hydrolysis as well as esterification with high efficiency and substrate specificity. However, in the pristine form they have inherent limitations such as lack of reusability and limited thermal and pH stability those restrict their uses in commercial applications. These limitations can be overcome by their immobilization on the suitable supports. Methods: In the present study a new poly(acrylic acid)-based functional nanogel was prepared by a simple surfactant free emulsification method and functionalized to poly(acrylic azide) form by a simple chemical protocol. Nanogels were characterized by X-Ray diffraction (XRD), Fourier Transform Infra Red (FTIR) spectroscopy, and transmission electron microscopy (TEM) to get evidence of the network formation and post reaction. The well characterized precursor nanogel and its functional derivatives were used as supports to immobilize lipase (triacyl glycerin). The activity assay of the immobilized lipase was carried out by the standard assay method. The catalytic potential of the immobilized lipase was evaluated in hydrolytic reactions using p-nitrophenol palmitate as substrate. Results: Immobilization enhanced the lipase activity and the structure of the nanogels made significant difference in enhancing their activity as the lipase immobilized on poly(Acryl azide)-cl-divinylbenzene nanogel exhibited the higher activity than the lipase immobilized on the precursor nanogel. Also, its activity was far higher than the free lipase. The immobilized lipase exhibited thermal and pH stability, which is not possible with the free lipase. Conclusion: The lipase was immobilized by the covalent linkages. The immobilized lipase exhibited good activity, storability and reusability. These results were dependent on the nanogel structure. Hence, a suitable nanogel can be tailored to obtain the maximum gains of immobilization. The reported results have good technological potential.