Carbonic anhydrase (CA) is one of nature's fastest enzymes and can dramatically improve the economics of carbon capture under demanding environments such as coal-fired power plants. The use of CA to accelerate carbon capture is limited by the enzyme's sensitivity to the harsh process conditions. Using directed evolution, the properties of a β-class CA from Desulfovibrio vulgaris were dramatically enhanced. Iterative rounds of library design, library generation, and high-throughput screening identified highly stable CA variants that tolerate temperatures of 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 translates to a 4,000,000-fold improvement over the natural enzyme. At pilot scale, the evolved catalyst enhanced the rate of CO 2 absorption 25-fold compared with the noncatalyzed reaction.carbonic anhydrase | directed evolution | carbon capture R eleasing over 9 billion metric tons of CO 2 worldwide each year, coal-fired power plants are the leading anthropogenic source of CO 2 emission. A potential solution to reduce the release of CO 2 into the atmosphere is the implementation of carbon capture and sequestration (CCS) technology on coal-and natural-gas-fired power plants. Currently, one of the most viable postcombustion CCS technology options uses an amine solvent to remove CO 2 from the flue gas (1). Unfortunately, the large amount of energy required to release the CO 2 and regenerate the solvent would significantly increase the cost of electricity generated (2). The ideal solvent capture process uses a solvent such as an aqueous amine with fast CO 2 absorption kinetics and a low heat of desorption to minimize the solvent regeneration energy. However, a high rate of CO 2 absorption kinetics for an amine solvent correlates with a higher temperature of desorption, whereas solvents with low heat of desorption tend to have much slower adsorption kinetics (3, 4).With reaction rates approaching the limits of diffusion, carbonic anhydrase (CA) is one of the fastest enzymes known. The active site of CAs can turnover CO 2 and water to bicarbonate and a proton up to a million times per second, and are used by almost every living organism to maintain pH balance and transport carbon dioxide. It has been shown that CAs can be used to accelerate the capture of CO 2 (5) by serving as a catalyst in alkaline capture solvents with slow absorption kinetics (6, 7). The potential improvements of CAs on CCS process economics stems from several considerations. The faster absorption and desorption kinetics allows for smaller processing equipment with reduced capital and operating costs (6). The improved kinetics also allows the use of lower temperature capture and solvent regeneration process conditions, and decreases energy losses in the capture process. Another benefit is the improved range of solvent candidates with attractive thermochemical stability (e.g., low vapor pressure, low formation of heat stable salts, etc.), but otherwise unacceptable unca...