Nano-magnesium aided activity enhancement and biophysical characterization of a psychrophilic α-amylase immobilized on graphene oxide nanosupport

In the current literature we have devised an immobilization technique for conferring psychrostability to a cold active α-amylase (amy) enzyme by the use of magnesium nanoparticle (MgNP) and graphene oxide (GO). The GO-MgNP-amy nanocomposite showed enhanced enzymatic activity and thermostability at both upper (90°C) and lower (8°C) temperature extremes. The GO-MgNP-amy showed increased affinity towards substrate, reflected in the decrease in its Km by 2.35 and 14.9-fold at 8°C and 90°C, respectively, than the untreated enzyme. GO-MgNP-amy showed 2.34-fold and 4.29-fold increase in Vmax at 8°C and 90°C, respectively, than the untreated enzyme. When compared to native enzyme at 90°C, GO-MgNP-amy had t1/2 (half life) increased by 44-fold with simultaneous increase in Ed by 1.9-fold. Again at 8°C, GO-MgNP-amy had t1/2 increased by 6.48-fold with simultaneous increase in Ed by 2.21-fold when compared to the native enzyme. The enzymatic activity of GO-MgNP-amy was retained even after 12 repeated uses and showed storage stability at 4°C for more than 120 days. The ability of GO-MgNP to sustain and aggravate enzyme activity and stability at temperatures beyond the optimal range can be utilized in bioprocessing industries which requires functioning at these extreme ranges of temperature.