Abstract
Bio-calcification is a natural phenomenon catalyzed by the urease enzyme, which is produced by a wide range of bacterial strains. The bio-calcification process relies on several physicochemical factors like pH, Ca2+, inoculum size (serve as a nucleation site), temperature, etc. In this study, seven urease-producing bacteria (BS-1-BS-7) were isolated from the garden soil of the two locations and the soil collected from a cave located at Sahastradhara, Dehradun Uttarakhand, India. These isolates were tested for urease activity and CaCO3 precipitation. Among the bacterial isolates, BS-6 produced the maximum ammonium ions and CaCO3 precipitate (14.6 mg/50 ml) and therefore it was selected for the optimization study. The two important factors – inoculum size (4%, 12%, and 20%; OD value 1.2 at 600 nm) and CaCl2 concentration (25, 50, and 100 mM) were optimized for bio-calcification process (CaCO3 precipitation). The optimum inoculum size and CaCl2 concentration for the CaCO3 precipitation by the isolate BS-6 were found to be 12% and 50 mM, respectively. Two-way ANOVA (analysis of variance) indicates that both factors, inoculum size and CaCl2 concentration significantly (p < 0.05) affect the CaCO3 precipitation. The present study signifies the role of Ca2+ and inoculum size in the bio-calcification process. The selected bacterial strain BS-6 was further identified as a novel strain Advenelle sp. AV1 based on the 16S rRNA sequencing. This is the first report that shows Advenelle sp. AV1 as urease producing and bio-calcite forming bacteria.
Authors’ contributions
SG & PT: Conducted experiments, collected data, and analyzed samples. VS: Experimental design, supervision, Data analysis, Writing – draft, review, and editing. AD: Conceptualized, Supervision, Writing – review and editing, Funding resources, Project administration, Funding acquisition.
Disclosure statement
No potential conflict of interest was reported by the author(s).