Engineered Escherichia coli with Periplasmic Carbonic Anhydrase as a Biocatalyst for CO 2 Sequestration

Abstract

ABSTRACT Carbonic anhydrase is an enzyme that reversibly catalyzes the hydration of carbon dioxide (CO 2 ). It has been suggested recently that this remarkably fast enzyme can be used for sequestration of CO 2 , a major greenhouse gas, making this a promising alternative for chemical CO 2 mitigation. To promote the economical use of enzymes, we engineered the carbonic anhydrase from Neisseria gonorrhoeae ( ng CA) in the periplasm of Escherichia coli , thereby creating a bacterial whole-cell catalyst. We then investigated the application of this system to CO 2 sequestration by mineral carbonation, a process with the potential to store large quantities of CO 2 . ng CA was highly expressed in the periplasm of E. coli in a soluble form, and the recombinant bacterial cell displayed the distinct ability to hydrate CO 2 compared with its cytoplasmic ng CA counterpart and previously reported whole-cell CA systems. The expression of ng CA in the periplasm of E. coli greatly accelerated the rate of calcium carbonate (CaCO 3 ) formation and exerted a striking impact on the maximal amount of CaCO 3 produced 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 periplasmic ng CA can successfully serve as an efficient biocatalyst for CO 2 sequestration.