Author(s)

Giulia Santomauro, Johannes Baier, Wanjing Huang, Stefan Pezold, Joachim Bill

Institute for Materials Science, University of Stuttgart, Stuttgart, Germany.

Calcium carbonate (CaCO₃) occurs in the three polymorphs calcite, aragonite and vaterite. The formation of these crystals in inorganic solutions is influenced by parameters like pH, temperature or impurities. Living freshwater microalgae can also induce the formation of CaCO₃ when they live in a suitable environment containing saturated amounts of Ca²⁺. Through this biologically induced biomineralization only the formation of the polymorph calcite has been reported yet. We investigated the precipitates which have been formed in solutions containing the freshwater microalgae Scenedesmus obliquus and different zinc amounts (0, 3.27 and 6.53 mg Zn²⁺/l) by XRD and SEM. As references precipitates from the same solutions but without algae were investigated. We could show that the presence of living microalgae has a great influence on the precipitation of calcium carbonate crystals. In algae-containing media without or with a low zinc amount always calcite and aragonite are formed. In the corresponding medium with 6.53 mg Zn²⁺/l pure aragonite crystals were built. In contrast, in the inorganic, algae-free solutions without zinc, pure calcite is precipitated. Both inorganic solutions with zinc show major calcite precipitation and weak aragonite precipitation. Thus the algae cells advance significantly the formation of aragonite, which is enhanced by the presence of zinc cations in the media. Possible mechanisms are discussed.

CaCO₃ Polymorphs; Biomineralization; Zinc; Microalgae; XRD

G. Santomauro, J. Baier, W. Huang, S. Pezold and J. Bill, "Formation of Calcium Carbonate Polymorphs Induced by Living Microalgae," Journal of Biomaterials and Nanobiotechnology, Vol. 3 No. 4, 2012, pp. 413-420. doi: 10.4236/jbnb.2012.34041.