Expression and Characterization of Codon-Optimized Carbonic Anhydrase from Dunaliella Species for CO2 Sequestration Application

Abstract

Carbonic anhydrases (CAs) have been given much attention as biocatalysts for CO2 sequestration process because of their ability to convert CO2 to bicarbonate. Here, we expressed codon-optimized sequence of alpha-type CA cloned from Dunaliella species (Dsp-aCAopt) and characterized its catalyzing properties to apply for CO2 to calcite formation. The expressed amount of Dsp-aCAopt in Escherichia coli is about 50 mg/L via induction of 1.0 mM isopropyl-beta-d-thiogalactopyranoside at 20 A degrees C (for the case of intact Dsp-aCA, negligible). Dsp-aCAopt enzyme shows 47 A degrees C of half-denaturation temperature and show wide pH stability (optimum pH 7.6/10.0). Apparent values of K (m) and V (max) for p-nitrophenylacetate substrate are 0.91 mM and 3.303 x 10(-5) mu M min(-1). The effects of metal ions and anions were investigated to find out which factors enhance or inhibit Dsp-aCAopt activity. Finally, we demonstrated that Dsp-aCAopt enzyme can catalyze well the conversion of CO2 to CaCO3, as the calcite form, in the Ca2+ solution [8.9 mg/100 mu g (172 U/mg enzyme) with 10 mM of Ca2+]. The obtained expression and characterization results of Dsp-aCAopt would be usefully employed for the development of efficient CA-based system for CO2-converting/capturing processes.