Effect of the tryptone concentration on the calcium carbonate biomineralization mediated by Bacillus cereus

Five tryptone concentrations (0.2%, 0.4%, 0.6%, 0.8% and 1.0%) were evaluated on calcium carbonate biomineralization processes, using 0.5% of calcium acetate. A culture of Bacillus cereus , isolated from the gardens of The Universidad Pontificia Bolivariana (Medellin, Antioquia, Colombia) was used in all the assays. The experiments were monitored by pH measurements and mineralogical analyses of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Scanning electronic microscopy (SEM). Vaterite was the predominant polymorph in the precipitates after 6 days of the process. However, a considerable proportion of calcite appeared (above 30%) when the tryptone concentration was 0.4% or below. Additionally, the other experiments had a similar precipitate formation (between 3.2-3.6 g/L) except the assay using 0.2% of tryptone, which presented a low calcium carbonate production (1.79 g/L). A tryptone concentration below 0.4% would limit the bacterial metabolism and CO 2 formation, necessary for calcium carbonate production.