About This Project

Reducing CO2 levels is a significant technological focus in the fight against climate change today. Direct air capture and point-source capture are well-accepted methods of reducing CO2 concentrations but with cost concerns due to the inefficiency of CO2 absorption during CO2 capture. A potential solution to this problem is the CO2 hydrating enzymes, carbonic anhydrases (CAs), but the gap lies in the engineering of an ultra-stable CA that can endure the harsh conditions of CO2 capture.

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What is the context of this research?

The sequestration of CO2 from the atmosphere requires gigatone-scaled projects in order to be efficient and cost-effective. System efficiency is an important attribute of mitigation strategies which implement direct air capture (DAC) and point-source capture (PSC). However, in these systems, temperature changes necessitates high energy requirements, which include heating the solvent to release CO2 and cooling it for capture. CO2 capture materials with high absorption rate, which reduce cost by reducing the gas contactor size, typically have high CO2 regeneration energy, and vice versa. An enzymatic catalyst that is highly selective to CO2, highly active and durable, would therefore be necessary to help to increase absorption rate of the CO2, consequently reducing costs.

What is the significance of this project?

Carbonic anhydrases (CAs) are enzymes that convert CO2 to bicarbonate ions at an accelerated rate. The use of a CAs in DAC and PSC would enable fast CO2 absorption in capture solvents with low CO2 regeneration energy, resolving the trade off discussed above. CAs could enable efficient DAC and PSC with small temperature or pH swings if it can be stabilized in DAC or PSC processes, which may include high pH, temperature, or ionic strength. These enzymes can reduce PSC cost >30% vs standard methods. Protein engineering (PE) tools and systematic screens of natural variants, which are revolutionizing PE could produce next-generation ultrastable CAs, further enhancing PSC as well as DAC, which demands higher stability due to the enzyme quantities needed for the larger solvent volumes used.

What are the goals of the project?

Often, engineering proteins leads to a trade-off in its properties, for example, higher thermostability at the expense of high catalytic efficiency or vice-versa. Most engineering attempts have been mainly towards thermostability, however, for applications such as CO2 capture technologies involving solvents such as K2CO3 or KOH, catalytic efficiency of CAs in such environments is also necessary. The concentration of K2CO3 in CO2 capture solutions can vary but is often in the range of 20% to 40% by weight for post-combustion capture. The main goal is to engineer an ultrastable CA that not only is thermostable but also resists inactivation in the presence of the different solvents used in DAC and PSC processes. We also aim to develop a systematic workflow of engineering carbonic anhydrases.