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Molecular Dynamics (MD) simulation is a computational method for analyzing the physical movements of atoms and molecules allowed to interact for a fixed duration of time. In this study, the thermal stability of carbonic anhydrase, which catalyzes the reaction of water and carbon dioxide, was investigated. Our simulations were performed in a box of water at four different temperatures, 300 K, 310 K, 320 K, and 330 K. The duration of each simulation was 100 ns, and thereafter the hydrogen bonds, Solvent Accessible Surface Area (SASA), as well as Root Mean Square Deviation (RMSD) were analyzed. Moreover, cluster analysis was done to identify representative structures at each temperature. The results showed that changing the temperature did not significantly impact the number of hydrogen bonds. The SASA had more fluctuation when the temperature increased. Moreover, the higher the temperature of the simulation was, the more clusters were obtained. The higher number of clusters indicates higher conformational flexibility and less-stable conformers forming during the simulation. [ABSTRACT FROM AUTHOR]

Mineral carbonation is the most effective carbon capture technique, but carbon dioxide (CO2) conversion is limited by the slow hydration rate of CO2 (<10−1 s−1). A biological solution exists: carbonic anhydrase (CA) efficiently hydrates CO2 at a turnover rate of ≈106 s−1 under ambient conditions, making it an extremely attractive candidate for industrial post‐combustion CO2 capture. However, high cost and poor long‐term stability impose a technical barrier to its practical uses. Here, a genetically engineered Corynebacterium glutamicum (C. glutamicum) is introduced as a robust cell display platform for the in situ stabilization and low‐cost production of CA. The enzyme is displayed in the mycolic layer with porin B as an anchoring protein with (GGGGS)2 as a spacer. The cell‐displayed CA exhibits no significant inactivation of the CO2 hydration activity for at least one month at 37 °C. Its denaturation rate constant at 50 °C (0.07) is an order of magnitude lower than that of free CA (0.52–0.54). This study demonstrates that a structurally robust cell template allows the effective stabilization of CA, suggesting the C. glutamicum‐based cell display as a promising technique to achieve highly efficient, sustainable, and low‐cost CO2 capture for industrial applications. [ABSTRACT FROM AUTHOR]

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Carbonic anhydrase (CA), a ubiquitous enzyme that catalyzes the reversible hydration of CO2, is known to be involved in the formation of CaCO3 biominerals and is currently used for biomimetic CO2 mineral sequestration. However, its specific role(s) in calcium carbonate (bio)mineralization is poorly understood. Here we show that CA catalyzes the formation of the reactive precursors (i.e., HCO3− and CO32− ions) required for mineralization, accelerates the precipitation of metastable amorphous calcium carbonates and their solution-mediated conversion into crystalline calcite, which grows via a non-classical nanoparticle aggregation mechanism that facilitates CA occlusion. Ca+ and CO32− ions promote the partial unfolding and oligomerization of CA, resulting in fibril- and sheet-like supramolecular assemblies that template nanostructured calcium carbonate crystallization. By losing its catalytic activity following the observed conformational changes, CA elicits a mechanism for arresting calcium carbonate mineralization. Our results show that CA can play multiple, until now unrecognized, critical roles, namely, as an enzyme and structural protein in CaCO3 biomineralization and also helps to explain the observed loss of enzymatic activity during ex situ CO2 mineral sequestration. [ABSTRACT FROM AUTHOR]

We describe a mobile CO2 scrubbing platform that offers a greatly accelerated biomimetic sequestration based on a self-propelled carbonic anhydrase (CA) functionalized micromotor. The CO2 hydration capability of CA is coupled with the rapid movement of catalytic micromotors, and along with the corresponding fluid dynamics, results in a highly efficient mobile CO2 scrubbing microsystem. The continuous movement of CA and enhanced mass transport of the CO2 substrate lead to significant improvements in the sequestration efficiency and speed over stationary immobilized or free CA platforms. This system is a promising approach to rapid and enhanced CO2 sequestration platforms for addressing growing concerns over the buildup of greenhouse gas. [ABSTRACT FROM AUTHOR]

A biomimetic catalyst was prepared through the self-assembly of a bolaamphiphilic molecule with histidine moieties for the sequestration of carbon dioxide. The histidyl bolaamphiphilic molecule bis(N-α-amidohistidine)-1,7-heptane dicarboxylate has been synthesized and self-assembled to produce analogues of the active sites of carbonic anhydrase (CA) after association with Zn2+ ions. Spectroscopic analysis demonstrated the coordination of the Zn2+ ions with histidine imidazole moieties, which is the core conformation of CA active sites. The Zn-associated self-assembly worked as a CA-mimetic catalyst that shows catalytic activity for CO2 hydration. Evaluation of the kinetics of using para-nitrophenylacetate revealed that the kinetic parameters of the CA-mimetic catalyst were maximized at the optimal Zn concentration and that excess Zn ions resulted in deteriorated catalytic activity. The performance of the CA-mimetic catalyst was enhanced by changing the pH value and temperature of the reaction, which implies that the hydrolysis of the substrate is the rate-determining step. The catalyst-assisted sequestration of CO2 was demonstrated by CaCO3 precipitation upon the addition of Ca2+ ions. This study offers an easy way to prepare enzyme analogues for CO2 sequestration through the self-assembly of bolaamphiphile molecules with designer biochemical moieties. [ABSTRACT FROM AUTHOR]

1-Palmitoyl-2-oleoyl- sn-glycero-3-phosphocholine (POPC) liposomes containing CaCl2 were prepared in Tris solution. The optimal initial pH and temperature were determined based on the kinetics of bulk crystallization of CaCO3 and to depress the leakage of Ca2+ from liposomes. The CaCO3 particles were formed by mixing the liposome suspension and CO2-saturated water, as analyzed with the scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy. The liposomal reaction system can be utilized for the formation of fine CaCO3 particles through sequestration of CO2. [ABSTRACT FROM AUTHOR]

Using recombinant DNA technology, we constructed a dual fusion gene expression plasmid, pRCAH-30, encoding carbonic anhydrase (CA) from the cyanobacterium Synechocystis sp. PCC6803, an R5 peptide sequence, and an affinity (His) tag, to allow the simultaneous purification and immobilization of the encoded fusion enzyme, termed RCAH. The expressed fusion protein was approximately 30 kDa, and could be rapidly purified using affinity resins. To enhance enzyme activity, the R5 peptide facilitated immobilization by means of silicification with tetramethoxysilane; the aggregated particles were approximately 300 nm in diameter. Activity tests revealed that the enzyme functioned optimally between pH 7.0 and 7.5; maximum stability was achieved between 25 and 45°C, at pH 6.0 ∼ 8.0. Activity of the fusion enzyme persisted, even after encapsulation by biomimetic silicification. In fact, silicone embedding stabilized the enzyme structure, thereby increasing its stability and reusability rate under different environmental conditions. In addition, the silicified enzyme reduced waste CO gas from 800 to 42 ppm, resulting in a gas capture rate of 94.7% after conversion. Thus, the construct developed in this study can be effectively utilized for the sequestration of industrial waste CO gas. [ABSTRACT FROM AUTHOR]

The enzyme bovine carbonic anhydrase (BCA) has been immobilized in the chitosan-alginate system for the first time, to catalyze the conversion of CO[sub 2] to HCO[sub 3]-. Chitosan-coated alginate beads are a biodegradable and environmentally benign matrix, chosen for application of the enzyme in a novel biomimetic CO[sub 2] sequestration system. The feasibility of the system and immobilization of the enzyme were demonstrated in our earlier studies [1–3]. Optimization of the matrix to improve the retention time of the enzyme in an encapsulated form is the subject of the present study. The improvement in the molecular weight cut-off of the beads was accomplished by adjusting the crosslinking conditions, coating composition, and molecular weight of the system. The quantity of enzyme released from the system was measured by a Bio-Rad protein assay. Poly-L-lysine was also used as a coating reagent for comparison purposes. The presence of a coating on the alginate beads was verified by Kjeldahl analyses. The difference in the microstructures of alginate and chitosan/alginate beads was demonstrated by SEM studies. Mineralization of the chitosan/alginate matrix in the presence of CaCO[sub 3] was also studied by FT-IR, to assess the possibility of using the beads continuously in a bioreactor. [ABSTRACT FROM AUTHOR]