Engineered Escherichia coli with Periplasmic Carbonic Anhydrase as a Biocatalyst for CO2Sequestration
ABSTRACTCarbonic anhydrase is an enzyme that reversibly catalyzes the hydration of carbon dioxide (CO2). It has been suggested recently that this remarkably fast enzyme can be used for sequestration of CO2, a major greenhouse gas, making this a promising alternative for chemical CO2mitigation. To promote the economical use of enzymes, we engineered the carbonic anhydrase fromNeisseria gonorrhoeae(ngCA) in the periplasm ofEscherichia coli, thereby creating a bacterial whole-cell catalyst. We then investigated the application of this system to CO2sequestration by mineral carbonation, a process with the potential to store large quantities of CO2.ngCA was highly expressed in the periplasm ofE. coliin a soluble form, and the recombinant bacterial cell displayed the distinct ability to hydrate CO2compared with its cytoplasmicngCA counterpart and previously reported whole-cell CA systems. The expression ofngCA in the periplasm ofE. coligreatly accelerated the rate of calcium carbonate (CaCO3) formation and exerted a striking impact on the maximal amount of CaCO3produced under conditions of relatively low pH. It was also shown that the thermal stability of the periplasmic enzyme was significantly improved. These results demonstrate that the engineered bacterial cell with periplasmicngCA can successfully serve as an efficient biocatalyst for CO2sequestration.