CO2 mineralization by the recombinant strains expressing thermostable carbonic anhydrases

Abstract

hyperthermophilic archaeon Thermococcus onnurineus NA1 emits carbon dioxide when producing H2 by oxidation of carbon monoxide or formate. As a strategy for reducing CO2 emission, we attempted to capture CO2 by precipitating to calcium carbonate minerals with the aid of carbonic anhydrase (CA). CA, one of the fastest known enzymes, is involved in the reversible hydration of CO2 to bicarbonate ions and protons and subsequently promotes the formation of CaCO3 in the presence of calcium cations. In this study, we selected thermostable CAs from thermophilic microbes such as Sulfolobus solfataricus and Metallosphera sedula, and a mesophilic CA from Acetobacterium woodii to test CA-mediated CO2 mineralization. Codon-optimized heterologous CA genes were introduced into T. onnurineus NA1 by double-crossover homologous recombination and the genes were overexpressed under the control of a strong promoter. At high temperatures, CA activity was determined by the electrometric method of Wilbur and Anderson, and CO2 mineralization was also tested by turbidity assay using UV/vis spectrophotometer. As a result, the recombinant CAs successfully accelerated CO2 mineralization to CaCO3.nate minerals with the aid of carbonic anhydrase (CA). CA, one of the fastest known enzymes, is involved in the reversible hydration of CO2 to bicarbonate ions and protons and subsequently promotes the formation of CaCO3 in the presence of calcium cations. In this study, we selected thermostable CAs from thermophilic microbes such as Sulfolobus solfataricus and Metallosphera sedula, and a mesophilic CA from Acetobacterium woodii to test CA-mediated CO2 mineralization. Codon-optimized heterologous CA genes were introduced into T. onnurineus NA1 by double-crossover homologous recombination and the genes were overexpressed under the control of a strong promoter. At high temperatures, CA activity was determined by the electrometric method of Wilbur and Anderson, and CO2 mineralization was also tested by turbidity assay using UV/vis spectrophotometer. As a result, the recombinant CAs successfully accelerated CO2 mineralization to CaCO3.