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Extensive efforts are being made to use biocatalysts for addressing an important millennium development goal i.e. global warming/climate change with recourse to CO capture valorisation and storage (CCVS). New advanced enzyme-based catalysts with significantly improved catalytic properties and stability have been discussed in detail with specific reference to carbonic anhydrase for biomimetic CO sequestration. [ABSTRACT FROM AUTHOR]

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 CO 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 ( K), maximum reaction velocity ( V), and storage stability of free CA and SEN-CA. The V of SEN-CA (0.02857 mmol/min/mg) and free enzyme (0.02029 mmol/min/mg) is almost similar. K 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 CO to carbonate was 61 mg of CaCO/mg of CA and 20.8 mg of CaCO/mg of CA using SEN-CA and free CA, respectively. [ABSTRACT FROM AUTHOR]

Abstract: Carbonic anhydrase (CA) has been immobilized on chitosan beads and has been tested for its activity using p-NPA. CA immobilized chitosan beads were further tested for targeted application of carbonation reaction to convert CO2 to CaCO3. It was observed that onset time for precipitation of CaCO3 was 40s for immobilized catalyst as compared to non-catalyzed system (100s). Mechanistic and kinetic aspects have been addressed for immobilized catalyst as well as free CA using p-NPA assay. K m and V max of the immobilized CA was observed to be 2.36mM and 0.54μmoles/min/ml as compared to K m and V max of 0.87mM and 0.93μmoles/min, respectively, for free CA. Storage stability test was conducted up to 20 days and it was observed that at −20°C, the Half Life Period (HLP) of immobilized CA was 216h as compared to 192h for free CA whereas at 25°C the HLP for immobilized and free CA was observed to be 456h and 408h, respectively. [Copyright &y& Elsevier]