Preparation and characterization of a green nano-support for the covalent immobilization of glucoamylase from Neurospora sitophila

The preparation of green nano supports for the covalent immobilization of enzymes is of special interest both from the economic and environmental point of view. In this contribution, we report on the synthesis of phytochemicals coated silver nanoparticles, which were used as a novel green support for the covalent immobilization of glucoamylase isolated from Neurospora sitophila. The aqueous extract of Fagonia indica was used as a source of reducing and capping agents for the reduction of silver ions into silver nanoparticles. The prepared nanoparticles were characterized by various analytical techniques. UV-visible spectroscopy was used to detect the characteristic surface plasmon resonance bands (426,438 nm) of the silver nanoparticles. The biosynthesized silver nano particles were mostly spherical in shapes with an average particle size of 30-40 nm (TEM and DLS measurements). X-ray diffraction and energy dispersive X-ray studies confirmed the face centered cubic crystalline form and elemental composition of the biogenic silver nanoparticles respectively. FTIR study revealed that plant polyphenolics and protein were mainly involved in the reduction and capping of silver ions. Glucoamylase from Neurospora sitophila was covalently immobilized to these nanoparticles via EDC (1-(3-(dimethylamino) propyl) 3-ethylcarbodiimidehydrochloride) coupling reaction. The immobilized enzyme exhibited higher pH and thermal stabilities as compared to the free enzyme. The kinetic constant (K-M) value for the immobilized glucoamylase was higher (0.73 mg/mL) than its free counterpart (0.44 mg/mL), whereas the V-max value was slightly higher for the immobilized glucoamylase. The findings of this study conclude that the newly developed green method for the synthesis of green nano-support is simple, cost effective and could be successfully used for the immobilization of various enzymes and other macromolecules. (C) 2016 Elsevier B.V. All rights reserved.