Mineralization of Gaseous C[O.sub.2] by Bacillus megaterium in close environment system

Implication of ureolytic biocalcification process as an efficient carbon dioxide sequestration technology was evaluated with Bacillus megaterium culture growing in a closed environment system. In three experimental sets containing either 35% v/v C[O.sub.2] in headspace (set 1) or 50 mM urea insolution (set 3) or both (set 2), change in headspace C[O.sub.2], soluble calcium, and pH were monitored during 8 days of incubation. In absence of urea, headspace C[O.sub.2] content continued to increase in set 1 (up to 48% v/v) without any carbonate precipitation. However, carbonate precipitation were obvious in urea containing sets (sets 2 and 3) utilizing all the added calcium (25 mM) in just 2 and 6 days, respectively. No headspace C[O.sub.2] could be detected in set 2 at the end of experimental period, and analysis suggested that this was majorly (>53%) attributed to the solubility trapping phenomenon. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis revealed that the precipitates were made up of calcite and major fraction of vaterite polymorph of CaC[O.sub.3]. Keywords Bacillus megaterium * C[O.sub.2] biomineralization * Solubility trapping * Carbonate precipitation