Developing a hybrid carbonic anhydrase with exceptional high temperature and alkaline environments resistance for efficient CO2 capture from air

Abstract

Reducing atmospheric CO₂ levels to combat global warming is a pressing concern today. Numerous methods have been employed to capture CO₂ from flue gases. One particularly promising approach is the use of carbonic anhydrases (CAs) as biocatalysts for the rapid conversion of CO₂ to H₂CO₃. However, the widespread application of CAs for CO₂ capture has been hampered by their inherent instability under real-world conditions. In this study, we have successfully engineered a chimeric carbonic anhydrase with vastly improved physicochemical properties, particularly with respect to its resilience to high temperatures, alkaline pH, and saline environments. Using computational design, we created various hybrid CAs with enhanced resistance to elevated temperatures. Among them, a chimeric CA known as SPS, generated by domain exchange between SazCA and PmCA, exhibited superior heat stability compared to its parent CAs. SPS showed 10 % higher enzymatic activity and retained 80–13 % of its activity during a period of 3 h to 24 h of incubation at 100℃. SPS's apparent k_cat and K_m values were 4.84 × 10⁸ s⁻¹ and 13.7 mM, respectively. Structural analysis revealed that SPS forms dimers, which contributes to its robustness. Furthermore, we introduced modifications in the form of SPS_1 and SPS_2 variants by incorporating one or two loop sequences from the halotolerant dCAII into SPS. These modifications significantly improved the stability of the CA in alkaline and saline conditions. In particular, SPS showed remarkable efficiency in hydrating CO₂ in seawater. Given these compelling results, we propose that hybrid CAs such as SPS, SPS_1, and SPS_2 hold great promise for facilitating CO₂ hydration in a wide range of applications.

Synopsis

Greenhouse gas sequestration is an immediate need. This study reports an engineered and highly stable carbonic anhydrase for CO₂ sequestration and greenhouse gas reduction.