Corynebacterium cell display of carbonic anhydrase for carbon dioxide hydration and mineralization

Abstract

Mineral carbonation is the most effective carbon capture technique

however, the conversion rate of $CO_2$ is generally below $10^{-1} s^{-1}$, which is too low for industrial applications. A biological solution exists. A high-ly efficient biocatalyst, carbonic anhydrase (CA), exhibits a high turnover rate of ~ $10^{6} s^{-1}$ under ambient conditions. Unfortunately, its practical use is limited by poor stability and a high cost for its production and purification. Here we introduce a robust whole-cell platform for the efficient production and stabilization of CA by genetically displaying CA in the mycolic layer of Corynebacterium glutamicum. In terms of expression level and enzymatic activity, an optimal anchoring protein was porin B with a triplet of GGGGS as a spacer. The whole-cell catalyst maintained about 60 % of its initial activity at $60^\circ C$ for 24 h, which was about 6 times higher than that of free CA. It was also significantly higher than E. coli-based whole-cell catalyst previ-ously reported. Our analysis indicate that the structural integrity of the cell display platform is critically im-portant for the thermal stability of CA. By facilitating the hydration of $CO_2$, our whole-cell catalyst enhanced the mineralization rate of $CO_2$, in the presence of calcium ions, $52.1 \pm 11.8 mg min^{-1}$, which was about 2 times higher than that without CA. Our study suggests that the Corynebacterium-based cell surface display can be a promising approach to the facile production and thermal stabilization of CA for efficient minerali-zation of post-combustion $CO_2$