Calcite Nanocrystal Production Using Locally Isolated Ureolytic Bacteria and Assessing Their Resistance to Extreme Conditions

Abstract

Microbially induced calcium carbonate precipitation (MICP) is an abundant process in nature and involves the microorganism's activities. Therefore, our aim was to characterize the crystals precipitated by locally isolated urease-producing bacteria (Sporosarcina pasteurii N4, Lysinibacillus boronitolerance N6, Bacillus sp. N2, and Bacillus sp. N5) and to evaluate their resistance under extreme conditions. The Fourier transform infrared spectroscopy analysis confirmed the presence of calcium carbonate in the precipitates. The X-ray diffraction analysis demonstrated that calcite is the dominant polymorph produced using strains. The scanning electron microscope micrograph showed that precipitated calcium carbonate was in the shape of nanocrystal aggregates. The size of particles ranged between 20 and 50 nm. All survived strains were halotolerant and were able to grow in acidic and alkaline medium, but at an optimal pH level of 7. Bacterial growth obtained in the temperature range of 20–47 °C. Also, they showed 44–70% viability after 28-day desiccation stress using flow cytometry. These local bacteria can tolerate extreme conditions as well as production of calcium carbonate, and this suggests that four local strains are suitable candidates for the MICP applications. They can be a good alternative to conventional methods in the soil stabilization and other MICP-related applications. © 2022, The Author(s), under exclusive licence to Shiraz University.