Bioprecipitation of calcium carbonate induced by Bacillus subtilis isolated in Brazil

- This study was considered as a preliminary investigation for the purposes of biocementation.
- B. subtilis isolated in Brazil was capable of bioprecipitating CaCO3 by pH change during biofilm formation.
- The crystal analysis was performed by SEM presenting round structures with lumps clustered.
- B. subtilis AP91applied in cementitious materials could promote pores and cracks filling by bioprecipitation of CaCO3.
- The results can contribute to expand the knowledge in bioprecipitation that could be applied in cementitious materials.

In view of the growing concern about improving the characteristics and durability of cementitious materials, additions of bacteria, mainly of the genus Bacillus, are being studied as pore and crack filling through calcium carbonate precipitation (CaCO3). In this sense, the present study tested the strain B. subtilis AP91, isolated from rice leaves of the early Agulha variety, in the precipitation of CaCO3 by means of the change of pH during the formation of biofilm, in order to verify the potential of use of this bacterium to close pores and cracks in cementitious materials. To this end, the strain B. subtilis AP91 was inoculated in the B4 precipitation medium. The analysis of bacterial biofilm production and the evaluation of the morphology of precipitated crystals were performed using a Scanning Electron Microscope (SEM) and CaCO3 was quantified by the difference of mass retained on the filter with 2 μm micropores. The results showed that the bacterium B. subtilis AP91 has high capacity for CaCO3 precipitation, and may have advantageous applications in the closure of pores and cracks in cementitious materials.