Process Biochemistry, Vol.73, 38-46, 2018
Efficient carbon dioxide sequestration by using recombinant carbonic anhydrase
Efficient biological carbon dioxide sequestration for slowing down the climate changes requires a highly active and stable carbonic anhydrase (CA). A CA from Mesorlazobium lad (i.e., MICA) was first over-expressed in E. coli via different vectors and a concentration of up to 5 g/L was obtained with pET32a( +). The whole cell biocatalyst was stable between pH 4.0 and pH 9.0 and maintained 82% activity within 6% salinity. The cations NH4+, K+, Na+, Mg2+, Ca2+ and Mn2+ did not affect the catalytic activity, while Co2+, Cu2+, and Zn2+ inhibited > 70% biocatalyst activity at 5 mM. The K-cat and Km of whole cell CA was observed to be 1.76 x 10(6)/s and 0.0133 mM, while that of the crude enzyme was of 2.35 x 10(6) s(-1) and 0.0364 mM, respectively. The effective diffusivity coefficient (De) of whole cell CA was 3.98 mu m(2)/s. Whole cell biocatalyst immobilized in 2% (w/v) agar could be reused for 6 times for CO2 sequestration and remained stable for 40 days. A novel two-column system with immobilized whole cell biocatalyst and recombinant MICA effectively converted 100% CO2 to CaCO3 within 3.5 min. This provides an alternative, eco-frienclly arid low-cost process for carbon capture and storage (CCS) in the future.