Induction of Calcium Carbonate by Pseudomonas Putida

The purpose of this research is to study how the bacteria Pseudomonas putida (DCB13) utilises calcium ions in a culture medium with carbon dioxide (CO2) to yield calcium carbonate (CaCO3). The bacteria strain P. putida is a dominant strain isolated from the dolomitic surfaces in areas of Karst topographies, Guizhou Province. The experimental method was as follows: a modified beef extract-peptone medium (beef extract 3.0 g, peptone 10 g, NaCl 5.0 g, CaCl2 2.0 g, glass powder 2.0 g, distilled water 1 L and a pH between 6.5 and 7.5) was inoculated with P. putida in order to attempt to induce the synthesis of CaCO3. The sample was then processed by centrifugation every 24 hours during the 7-day cultivation period. The pH, carbonic anhydrase (CA) activity, and the concentrations of both HCO3- and Ca2+ of the supernatant fluid were measured. Subsequently, precipitation in the culture medium was analyzed to confirm, or otherwise, the presence and if present, the formation of CaCO3. Methods used included X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM), and Energy Dispersive Spectroscopy (EDS). Results showed that P. putida can improve its pH value in this culture medium; concentrations of HCO3- and Ca2+ showed a significant decline over the duration of the cultivation period. CA activity reached its maximum during the second day; XRD, SEM and TEM all revealed the presence of CaCO3 as a precipitate. Additionally, these results did not occur in an aseptic control group: no detectable level of CaCO3 was yielded therein. In conclusion: P. putida can metabolise active materials such as secretase by its own growth and metabolism, and can either utilise atmospheric CO2, or respire, to induce CaCO3 production.