Difference between revisions of "Part:BBa K4665120"

Revision as of 13:44, 5 October 2023

Background

Biomineralisation is the process by which living organisms synthesise minerals (Dhami et al., 2013). One of the main metabolic pathways of microbially producing calcium carbonate utilizes the zinc metallo-enzyme carbonic anhydrase as the catalyst of the reaction (Chaparro-Acuña et al., 2019). This pathway produces no pollutant byproduct (as is often the case with other biomineralisation pathways) and extracts CO2 from the atmosphere as a substrate for the reaction catalyzed by the carbonic anhydrase.

SazCA is a thermostable α-carbonic anhydrase derived from the thermophilic bacterium *Sulfurihydrogenibium azorense.* SazCA has been characterised as the fastest known carbonic anhydrase to date, possessing a kcat/KM value of 3.5 × 108 M−1 s−1

SazCA facilitates the reversible hydration of carbon dioxide to bicarbonate and protons (CO2 + H2O -><- HCO3 + H+) (De Simone et al, 2015). This process creates alkaline conditions which increase the solubility of Ca2+ ions trapped on the extracellular matrix (EPS) of bacterial cells, which readily bond to HCO3- , facilitating the formation of calcium carbonate crystals (Anbu, et al. 2016).

CO2 and HCO3- are small molecules capable of diffusing in and out of cells, yet the intracellular activity of CA is significantly limited by the permeability of the cell membrane, as it restricts both the amount of substrate available for catalysis and the subsequent secretion of the product, reducing overall enzymatic efficiency (Jo **et al.*,* 2013). Therefore, the proposed approach is to express the protein on the surface of the cell, directly exposing it to extracellular concentrations of CO2, and bypassing cellular secretion of bicarbonate ions, which ultimately enhances the production of calcium carbonate on the surface of limestone cracks.

References

Anbu, P. et al. (March 1, 2016). Formations of calcium carbonate minerals by bacteria and its multiple applications. Springerplus 5(250). https://doi.org/10.1186/s40064-016-1869-2

Chaparro-Acuña, S.P., et al. (June, 2018). Soil bacteria that precipitate calcium carbonate: mechanism and applications of the process. Acta Agronómica 67(2). https://doi.org/10.15446/acag.v67n2.66109

De Luca, V. et al. (March 15, 2013). An α-carbonic anhydrase from the thermophilic bacterium Sulphurihydrogenibium azorense is the fastest enzyme known for the CO2 hydration reaction. Bioorganic & Medicinal Chemistry Letters, 21(6): 1465.1469. https://doi.org/10.1016/j.bmc.2012.09.047

Dhami, N.K., et al. ( May 2013). Biomineralization of calcium carbonate polymorphs by the bacterial strains isolated from calcareous sites. Journal of Microbiology and Biotechnology, 23(5): 707-714. https://doi.org/10.4014/jmb.1212.11087

De Simone, G., et al. (May 1, 2015). Crystal structure of the most catalytically effective carbonic anhydrase enzyme known, SazCA from the thermophilic bacterium Sulfurihydrogenibium azorense. Bioorganic & Medicinal Chemistry Letters, 1;25(9): 2002-2006. https://doi.org/10.1016/j.bmcl.2015.02.068

Jo, B.H. (October 3, 2013). Engineered Escherichia coli with Periplasmic Carbonic Anhydrase as a Biocatalyst for CO2 Sequestration. Applied and Environmental Microbiology. https://doi.org/10.1128/AEM.02400-13