Nanoparticle assisted activity optimization and characterization of a bacterial phytase immobilized on single layer graphene oxide

•MgN-phy showed enhanced activity and stability at 85 °C.•GO-MgN-phy showed increased half-life at 85 °C.•Lowered Km and increased Vmax for GO-MgN-phy 85 °C.•Enzymatic activity of GO-MgN-phy retained after 180 min incubation.•Stability of GO-MgN-phy enzyme system at 4 °C for more than 140 days.

A thermostable phytase is a need of the hour towards prevention of environmental pollution by accumulation of phosphate. In this study, an extracellular phytase was purified from a strain of Bacillus subtilis obtained from cattle sheds in 24 Parganas (Kolkata, West Bengal). The native enzyme showed optimum activity at 42 °C and pH 8.5. In presence of magnesium nanoparticle (MgN), the graphene oxide (GO) immobilized enzyme showed 2.40 fold increased activity at 42 °C and more than 20 fold activity increment at 85 °C. The GO-MgN-phy complex (phytase coupled to MgN immobilized on graphene oxide) showed a decrease in Km by 3.29 folds at 42 °C and 6 folds at 85 °C. Again, the enzyme system showed 3 fold and 5.5 fold increase in Vmax at 42 °C and 85 °C respectively than the untreated enzyme. Compared to the untreated enzyme, energy of activation (Ea) was lowered by 2.5 and 6 folds repectively at 42 °C and 85 °C for GO-MgN-phy. At 85 °C, the half life (t ½) for GO-MgN-phy was 29.5 times than that of untreated enzyme with energy of dissociation (Ed) being 1.45 fold higher than the untreated enzyme. Enzymatic activity of GO-MgN-phy was retained by 86.6%when tested for storage stability at 4 °C after 140 days. This nanoparticle assisted immobilization technique employed in developing a thermostable phytase enzyme could withstand high temperatures during the pelleting of animal feeds. The increased activity of the enzyme would be beneficial to breakdown phytic acid during storage of feeds.

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