The soluble protein related to shell regeneration (SPSR) plays an important role to repair the damaged shell. In this study, the SPSR was used as a biocatalyst to control the crystal growth and morphology during in vitro CaCO3 crystallization. Anion exchange fast protein liquid chromatography (FPLC) was applied to separate the SPSR constituents. Each fraction from purification of the SPSR was subjected to CaCO3 crystallization to identify the fraction's effect on controlling the CaCO3 crystal morphology. CaCO3 crystallization experiments were performed by mixing solutions of CaCl2 and purified SPSR in the presence of vaporized (NH4)(2)CO3. The morphology of the CaCO3 crystals was characterized by field emission scanning electron microscopy (FE-SEM). The synthesized CaCO3 was characterized by Fourier transform infrared spectroscopy (FT-IR) to reveal the type of crystals formed. In vitro CaCO3 crystallization process showed the effect of SPSR on the morphology change of CaCO3 crystals. We identified a condition for rapid crystal growth and specific morphology of CaCO3 in the presence of SPSR. Thus, our study confirms that SPSR governs CaCO3 crystallization and influences the observed crystal morphology. (C) 2012 Elsevier B.V. All rights reserved.