Simulation and practical investigation of carbonic anhydrase stability in an industrial solvent system of methyl diethanolamine for carbon dioxide capture.

Carbonic anhydrase owing to its potential as an industrial biocatalyst for carbon dioxide sequestration from flue gas has attracted considerable attention in solving global warming problems. A large body of research has been conducted to increase the thermal stability of carbonic anhydrase from different sources against the harsh operational conditions of CO2 capture systems. In contrast to cost-intensive protein engineering methods, solvation with aqueous-organic binary mixtures offers a convenient and economical alternative strategy for retention of protein structure and stability. This study aimed to examine the stabilizing effect of methyl diethanolamine (MDEA) as a component of an aqueous-organic solvent mixture on human carbonic anhydrase II (HCA II) at extreme temperatures. Computational and also spectroscopic examinations were employed for tracking conformational changes and stability evaluation of HCA II in 50:50 (vol %) water: MDEA binary mixture at high temperature. Molecular dynamic (MD) simulation studies predicted the high thermal stability of HCA II in the presence of MDEA. UV absorbance spectra confirmed the thermo-stabilizing effect of the binary solvent mixture on HCA II. While the enzymatic activity of HCA II at 25 °C in the presence of 10, 25, and 50 (vol%) of MDEA was substantially increased, no obvious effect on retention of HCA II activity in the water-MDEA binary solvent mixture at 85 °C was seen. It is shown that the solvation of HCA II in the presence of MDEA could result in the prevention of aggregate formation in high temperatures but not functional stability.Communicated by Ramaswamy H. Sarma.

Rational design engineering of a more thermostable Sulfurihydrogenibium yellowstonense carbonic anhydrase for potential application in carbon dioxide capture technologies.

Implementing hyperthermostable carbonic anhydrases into CO2 capture and storage technologies in order to increase the rate of CO2 absorption from the industrial flue gases is of great importance from technical and economical points of view. The present study employed a combination of in silico tools to further improve thermostability of a known thermostable carbonic anhydrase from Sulfurihydrogenibium yellowstonense. Experimental results showed that our rationally engineered K100G mutant not only retained the overall structure and catalytic efficiency but also showed a 3 °C increase in the melting temperature and a two-fold improvement in the enzyme half-life at 85 °C. Based on the molecular dynamics simulation results, rearrangement of salt bridges and hydrogen interactions network causes a reduction in local flexibility of the K100G variant. In conclusion, our study demonstrated that thermostability can be improved through imposing local structural rigidity by engineering a single-point mutation on the surface of the enzyme.