Carbonic anhydrase as a tool to mitigate global warming

The global average temperature breaks the record every year, and this unprecedented speed at which it is unfolding is causing serious climate change which in turn impacts the lives of humans and other living organisms. Thus, it is imperative to take immediate action to limit global warming. Increased CO2 emission from the industrial sector that relies on fossil fuels is the major culprit. Mitigating global warming is an uphill battle that involves an integration of technologies such as switching to renewable energy, increasing the carbon sink capacity, and implementing carbon capture and sequestration (CCS) on major sources of CO2 emissions. Among all these methods, CCS is globally accepted as a potential technology to address this climate change. CCS using carbonic anhydrase (CA) is gaining momentum due to its advantages over other conventional CCS technologies. CA is a metalloenzyme that catalyses a fundamental reaction for life, i.e. the interconversion of bicarbonate and protons from carbon dioxide and water. The practical application of CA requires stable CAs operating under harsh operational conditions. CAs from extremophilic microbes are the potential candidates for the sequestration of CO2 and conversion into useful by-products. The soluble free form of CA is expensive, unstable, and non-reusable in an industrial setup. Immobilization of CA on various support materials can provide a better alternative for application in the sequestration of CO2. The present review provides insight into several types of CAs, their distinctive characteristics, sources, and recent developments in CA immobilization strategies for application in CO2 sequestration.

Enzymatic characteristics of immobilized carbonic anhydrase and its applications in CO2 conversion

Native carbonic anhydrase (CA) has been widely used in several different applications due to its catalytic function in the interconversion of carbon dioxide (CO₂) and carbonic acid. However, subject to its stability and recyclability, native CA often deactivates when in harsh environments, which restricts its applications in the commercial market. Maintaining the stability and high catalytic activity of CA is challenging. Immobilization provides an effective route that can improve enzymatic stability. Through the interaction of covalent bonds and van der Waals forces, water-soluble CA can be combined with various insoluble supports to form water-insoluble immobilized CA so that CA stability and utilization can be greatly improved. However, if the immobilization method or immobilization condition is not suitable, it often leads to a decrease in CA activity, reducing the application effects on CO₂ conversion. In this review, we discuss existing immobilization methods and applications of immobilized CA in the environmental field, such as the mineralization of carbon dioxide and multienzyme cascade catalysis based on CA. Additionally, prospects in current development are outlined. Because of the many outstanding and superior properties after immobilization, CA is likely to be used in a wide variety of scientific and technical areas in the future.