Single enzyme nanoparticle for biomimetic CO2 sequestration

Abstract

Nanoparticle technology is being increasingly used in environmental sciences. We prepared single enzyme nanoparticle (SEN) by modifying the surface of carbonic anhydrase (CA) with a thin layer of organic/inorganic hybrid polymer. SEN-CA appears to be improving the stability of free enzyme. CA, as ubiquitously found enzyme, is involved in gaseous CO2 sequestration and is being looked as a promising candidate for combating global warming. We report here physical characterization of SEN-CA using transmission electron microscope (TEM), Fourier-transform infrared analysis (FTIR), X-ray diffraction analysis (XRD), and energy dispersive X-ray (EDX). Average size of SEN-CA particles appears to be in the range of 70-80 nm. We also report the effect of SEN formation on the kinetic parameters of free CA such as Michaelis-€“Menten constant (Km), maximum reaction velocity (Vmax), and storage stability of free CA and SEN-CA. The Vmax of SEN-CA (0.02857 mmol/min/mg) and free enzyme (0.02029 mmol/min/mg) is almost similar. Km has decreased from 6.143 mM for SEN-CA to 1.252 mM for free CA. The stabilization of CA by SEN formation results in improved the half-life period (up to 100 days). The formation of carbonate was substantiated by using gas chromatography (GC). The conversion of CO2 to carbonate was 61 mg of CaCO3/mg of CA and 20.8 mg of CaCO3/mg of CA using SEN-CA and free CA, respectively.