S116: Developing an Efficient Strategy for Enzyme Evolution: Creation of an Ultra-Stable Form of Carbonic Anhydrase for CO2 Capture

With a reaction rate approaching the limits of diffusion, carbonic anhydrases (CA’s) are one of the fastest enzymes known.  Its proposed use for carbon capture and storage in a coal-fired power plant is limited by its tolerance to molar concentrations of aqueous amine solvents, high pH, and temperature.  Here we show how directed evolution dramatically enhanced the properties of a β-class carbonic anhydrase from Desulfovibrio vulgaris.  Iterative rounds of screening and library designs identified highly stable CA variants.  The most stable variants can be placed amongst the most thermostable enzymes, tolerating temperatures up to 107°C in the presence of 4.2 M alkaline amine solvent at pH 10.0.  This increase in thermostability and alkali tolerance translated to a four million-fold improvement over the natural enzyme.  The evolved enzyme was used for the capture of CO₂ from flue-gas emission where it enhanced the rate of CO₂ absorption by 25-fold.