Seawater-derived ureolytic Vibrio sp. strain F-11 as a microbial agent for calcium carbonate biomineralization

This study investigates the strain F-11, a ureolytic Vibrio isolated from seawater, and its potential for microbially induced calcium carbonate precipitation (MICP). Based on morphological and biochemical characteristics together with 16S rRNA gene sequence analysis, strain F-11 showed the highest similarity to Vibrio alginolyticus (96.79%) and was therefore conservatively designated as Vibrio sp. F-11. Urease activity measured by Nessler-based ammonium assay was examined at different temperatures (24, 30, 36 °C) and pH values (6, 8, 10). Maximum ureolytic activity was observed between days 3 and 5at 30 °C and pH 8, reaching approximately 0.58 and 0.57 µmol min⁻¹ mg⁻¹ protein, respectively, whereas suboptimal conditions significantly reduced activity. Calcium carbonate precipitation occurred only on urea-CaCl₂ agar at pH 8; here, opaque white mineral deposits accumulated around bacterial colonies. Microscopic observations revealed rosette-like and spherical CaCO₃ crystals, while SEM images revealed compact, spherical precipitates. EDS spectra dominated by Ca, C, and O peaks confirmed the formation of CaCO₃ phases. In general, Vibrio sp. strain F-11 demonstrated effective biomineralization capacity and represents a promising MICP agent for future marine and cementitious biotechnological applications.