Abstract
Sporosarcina pasteurii (S. pasteurii) is bacterium notable for its highly efficient urea degradation ability. Due to its high urease activity, S. pasteurii has been successfully utilized in applications including solidifying soil or sand, termed “bio-concrete”. In addition to calcium carbonate precipitation, urease isolated from the jack bean plant was recently demonstrated to induce the formation of magnetic iron oxide particles from soluble ferrous ion in a designed reaction. However, it remained unknown if a similar magnetic material could be formed using whole cells with high urease activity under biocompatible conditions. Here, we demonstrated that magnetic iron oxide with a highly ordered structure could be formed on the surface of S. pasteurii cells with a theoretical product of 1.17 mg in a 2-mL reaction. Moreover, the cells surrounded by the precipitated magnetic iron oxide maintained their viability. Due to the simple cultivation of S. pasteurii, the process developed in this study could be useful for the green synthesis of magnetic iron oxide, basic research on the mechanism of magnetic microbial-induced precipitation (MIP), and related engineering applications.
Highlights
Microbial-induced precipitation (MIP) is a common phenomenon caused by chemical changes in the solution due to microbial metabolism, resulting in the deposition of metal ions
The urease activity of S. pasteurii plays an important role in microbial-induced precipitation (MIP), and it is highest in the exponential growth phase [19]
According to the S. pasteurii growth curve shown in Figure 1A, the culture reached the exponential phase at an optical density at 600 nm (OD600) of 2.0, and the corresponding cells were used for the magnet mineralization experiment
Summary
Microbial-induced precipitation (MIP) is a common phenomenon caused by chemical changes in the solution due to microbial metabolism, resulting in the deposition of metal ions. MIP has been applied in many fields, including bio-bricks [3], self-healing concrete [4], ground improvement [5], and the bioremediation of metal ions [6]. The cells of many different microbial species can induce MIP by similar mechanisms. These cells can increase the solution pH to make it alkaline and supply anions for precipitation. Synechococcus and sulfate-reducing bacteria are typical examples. Synechococcus can use CO2 to form HCO3 − in photosynthesis, thereby leaving free OH− that makes the pH sufficiently alkaline for CaCO3 precipitation [7].
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