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Homogenous Precipitation of Calcium Carbonate Polymorphs by Enzyme Catalyzed Reactions (Plenary lecture)

Precipitation processes of carbonate particles of different size, shape, and surface properties have been intensively investigated due to their importance in geo- and biosciences, and in numerous industrial applications. This lecture describes and discusses a conceptually new method for the precipitation of calcium carbonate polymorphs effectuated through catalytic decomposition of urea by urease enzymes in solutions of calcium salts. Specifically, this lecture discusses the influence of primary structures of plant (Canavalia ensifomis) and bacterial (Bacillus pasteurii) ureases on the nucleation and growth of carbonate precipitates. Our studies have shown that examined enzymes exert different influences on crystal phase formation and on development of unusual and fascinating morphologies of calcium carbonate polymorphs. These differences may be explained by the dissimilarity in their amino acid sequences and their different interactions with the surface of growing crystals during precipitation processes. Finally, this lecture demonstrates an example how different organisms in nature have ability to produce proteins with the same catalytic function, and how with the slight changes in their primary structure (amino acid sequence), they control the crystal phase and the morphology of calcium carbonate precipitates.

Calcium Carbonate Polymorphs; Urease; Precipitation

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