نبذة مختصرة : Master ; Several carbon dioxide (CO2) capture and storage (CCS) technologies have been developed for reduction of CO2 which is the major anthropogenic green house gas. As a new paradigm, there have been attempts to convert CO2 to valuable chemicals. Recently, as a mimic of natural biomineralization, use of carbonic anhydrase (CA) which is an enzyme catalyzing reversible hydration of CO2 to bicarbonate has been suggested to biologically convert CO2 to carbonate minerals. Purified bovine CA (BCA) has been commonly utilized in the previous studies. However, due to economical problem of BCA preparation, practical utilization on biological CO2 conversion has been limited. Here, we focused on biocatalytic capture by recombinant Neisseria gonorrhoeae carbonic anhydrase (NCA), followed by trapping as solid CaCO3 using whole cell biocatalyst.In the present work, we investigated conversion of CO2 to calcium carbonate (CaCO3) as a target model carbonate minerals by using economical recombinant whole cell biocatalyst. To our knowledge, this is the first report on usage of recombinant CA for biological CO2 conversion. Recombinant α-type CA originated from N. gonorrhoeae was highly expressed as a soluble form in Escherichia coli. We found that purified NCA (~99% purity) has comparable hydration activity to the commercial purified BCA. Furthermore, precipitation of CaCO3 was promoted by addition of calcium ion in the presence of NCA and the rate of forming crystal morphology (calcite) was also accelerated. Importantly, whole cell fraction without high cost purification steps also showed comparable conversion ability to the purified NCA and BCA. Collectively, economical recombinant CA in the form of whole cell biocatalyst can be practically applied for conversion of CO2 to high valuable carbonate minerals.
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