Abstract
Carbon capture can be realized effectively through isocitrate dehydrogenase reaction and the reaction rate was strongly affected by the environmental parameters such as pH and temperature. Enzyme immobilization was conducted to improve the enzyme stability during the capture process. By simply adsorbing enzyme on the surface of mesoporous silica foam, enzyme stability against temperature, pH and shear stress was improved. The immobilization process can be completed in 5 mins, and 0.87 U enzyme activity was kept for each gram of immobilization material. After 10 cycles, more than 50 percent of enzyme activity remained. The reusability and improved stability made immobilized ICDH a better candidate for large-scale application of carbon capture.
Highlights
Isocitrate dehydrogenases (ICDHs) from different species show vast varieties in their kinetics, structure, stability, and more important, cofactor-dependence [1]
Both carboxylation and decarboxylation activities were detected for ICDH from porcine heart and the optimum pH for decarboxylation and carboxylation was 8 and 6 respectively
The highest specific activity for carboxylation was achieved at pH 6 as 0.45 U /mg, and a decline of carboxylation activity was observed with increasing pH value
Summary
Isocitrate dehydrogenases (ICDHs) from different species show vast varieties in their kinetics, structure, stability, and more important, cofactor-dependence [1]. The NADdepend ICDHs are (a4b4) heterooctamers, existing in the mitochondria of eukaryotes cells with a function of decarboxylation in the tricarboxylic acid (TCA) cycle [2]. NADP-dependent ICDHs exist in both prokaryotes and eukaryotes, located in the cytosol, peroxisomes, and mitochondria, with a function of biosynthesis of fatty acids and amino acids. ICDHs was initially believed to only possess the decarboxylation function, while the discovery of reductive TCA cycle revealed its carboxylation activity [4]. In reductive TCA cycle, ICDH catalyzes the step that one mole of isocitrate is synthesized from one mole of ketoglutarate and carbon dioxide. Mesoporous materials, especially mesoporous silica foam (MSF), possess a highly ordered structure with nanometer pore size, providing a high surface area for enzyme adsorption [5]. Enzymes can directly bind the MSF through the hydrophilic attraction of the hydroxy group of the surface of MSF, and for advanced application, various active groups modified on the surface of MSF can facilitate enzyme loading with strong or specific binding [6]
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