High level of calcium carbonate precipitation achieved by mixed culture containing ureolytic and nonureolytic bacterial strains

This study demonstrates a remarkably high level of microbial-induced calcium carbonate precipitation (MICP) using a mixed culture containing TBRC 1396 (Priestia megaterium), TBRC 8147 (Neobacillus drentensis) and ATCC 11859 (Sporosarcina pasteurii) bacterial strains. The mixed culture produced CaCO3 weights 1·4 times higher than those obtained from S. pasteurii, the gold standard for efficient MICP processes. The three strains were selected after characterization of various Bacillus spp. and related species for their ability to induce the MICP process, especially in an alkaline and high-temperature environment. Results showed that the TBRC 1396 and TBRC 8147 strains, as well as TBRC 5949 (Bacillus subtilis) and TBRC 8986 (Priestia aryabhattai) strains, could generate calcium carbonate at pH 9-12 and temperature 30-40°C, which is suitable for construction and consolidation purposes. The TBRC 8147 strain also exhibited CaCO3 precipitation at 45°C. The TBRC 8986 and TBRC 8147 strains are nonureolytic bacteria capable of MICP in the absence of urea, which can be used to avoid the generation of undesirable ammonia associated with the ureolytic MICP process. These findings facilitate the successful use of MICP as a sustainable and environmentally friendly technology for the development of various materials, including self-healing concrete and soil consolidation.