Imobilização da anidrase carbônica de Sulfurihydrogenibium azorense no suporte a base de sílica SBA-15 com poros expandidos para captura de CO 2

Abstract

The increase in carbon dioxide (CO 2 ) emissions, mainly from the use of fossil fuels, has intensified the search for sustainable technologies aimed at mitigating environmental impacts, such as global warming. In this context, biological carbon capture and storage processes have stood out due to their higher selectivity and operation under mild conditions, reducing energy consumption compared to conventional methods, such as chemical absorption. Therefore, this work aimed to evaluate the immobilization of carbonic anhydrase, derived from the heterologous expression of the ArticExpress (DE3) strain of the thermophilic microorganism Sulfurihydrogenibium azorense, on mesoporous silica SBA-15 (Santa Barbara Amorphous-15) with expanded pores, aiming to obtain a biocatalyst with higher stability and efficiency for CO 2 capture. For this purpose, the enzyme was expressed in Escherichia coli, extracted by cell lysis, and analyzed in terms of catalytic activity and zeta potential. The SBA-15 support with expanded pores was synthesized via a hydrothermal route and characterized by nitrogen adsorption/desorption isotherms, Fourier-transform infrared spectroscopy, and point of zero charge, resulting in the formation of a structure with ordered pores. Meanwhile, for the biocatalyst obtained by physical adsorption (SBA-AC), the effects of pH, ionic strength, protein load, and contact time during immobilization were measured. Protein yields were higher than 90% under almost all conditions, indicating strong affinity of the enzyme extract for the support, and the condition of 50 mg of protein per gram of support showed the best overall performance, with recovered activity above 80%. In addition, the support not only promoted enzyme immobilization but also provided partial purification of the extract, selectively retaining carbonic anhydrase over other proteins present. Furthermore, the storage stability of SBA-AC biocatalysts and those chemically modified with glutaraldehyde (SBA-AC-GA) was monitored over 90 days, showing not only maintenance but also an increase in catalytic activity during this period, with an approximate 25% increment in relative activity for both cases. Therefore, the results of this work demonstrate that the immobilization of carbonic anhydrase on SBA-15 with expanded pores is a promising strategy for CO 2 capture, presenting high catalytic performance and elevated storage stability.