# Application of Microbially Induced CaCO\({}_{3}\) on the Reinforcement of Rock Discontinuity
## 2 Materials and Methodology  
### Sporosarcina pasteurii and Medium  
Currently, the most commonly used microbial mineralization technology involves urea bacteria, which are widely found in nature. _Sporosarcina pasteurii_ is a Gram-positive bacterium known for its ability to induce calcite precipitation from biological cementation by the production of urease [47]. In addition to _Sporosarcina pasteurii_, researchers have utilized Microc-occusureae, Proteus, Salmonella, Escherichia coli, and Staphylococcus [48]. _Sporosarcina pasteurii_ has been proposed for use as an ecologically sound biological construction material. Studies have demonstrated that when combined with plastic and hard minerals, _Sporosarcina pasteurii_ can form a material stronger than bone [21; 37; 49]. The bacterium is commonly used for MICP due to its non-pathogenic nature and its ability to produce high amounts of urease, which hydrolyzes urea to carbonate and ammonia [50]. _Sporosarcina pasteurii_ is preferred due to its classification as a spore-forming bacteria. Spore-forming bacteria can produce round or oval spores within the cell during the later stages of growth and reproduction. These spores have thick walls, low water content, and high-stress resistance, giving the bacteria strong environmental resilience. Additionally, under alkaline conditions, the urease activity of _Sporosarcina pasteurii_ surpasses that of other bacteria [51]. Recent studies have focused on the isolation of bacteria in alkaline conditions, with outcomes demonstrating the effective use of laboratory-extracted bacteria for repairing geological materials [2; 13; 51; 52; 53]. In this context, laboratory-extracted _Sporosarcina pasteurii_ (from the China General Microbial Culture Preservation Management Center (CGMCC), the number is 1.3687) was utilized to assess the reinforcement effect of microbially produced CaCO\({}_{3}\) on the shear strength of rock joints under a saline-alkaline environment. The purchased strains are in a freeze-dried powder form. The bacterial suspension used in the experiment was an activated bacterial suspension. The culture conditions of bacterial activation are as follows: 30 \({}^{\circ}\)C, 150 rpm, for about 5 days. The culture medium contained beef extract (5 g/L), peptone (5 g/L), and NaCl (5 g/L). After observing the turbidity of the bacterial solution, the mother solution was obtained by mixing the bacterial suspension with the neutral medium at a volume ratio of 1:100 for 48 h. The OD600 value was 1.411. The components of the saline-alkaline environment include sodium chloride (NaCl), magnesium phosphate (MgSO\({}_{4}\)), potassium chloride (KCI), and peptone (Table 2). Detailed information regarding the materials used for the domestication of bacteria in the saline-alkaline medium is presented in Table 2. The pH value of the medium was adjusted by 1 mol/L NaOH solution and 1 mol/L HCl solution. The pH value of the saline-alkaline medium was adjusted to 9, while the neutral medium was adjusted to pH 7. The pH of the solution was measured with a pH detector while adding NaOH or HCl solution until the desired value was reached. The bacteria were cultured by an incubator, with the incubation process lasting for 48 h at 150 r/min (revolutions per minute) and a temperature of 30 \({}^{\circ}\)C. The optimal densities of _Sporosarcina pasteurii_ were measured using an ultraviolet (UV) spectrophotometer. The UV \begin{table}
\begin{tabular}{l l l} \hline
**District** &
\begin{tabular}{l} **Area** \\ **(Thousand Hectares)** \\ \end{tabular} & **Percent** \\ \hline North America & 1575.5 & 1.65 \\ Mexico & 196.5 & 0.21 \\ South America & 12,916.3 & 13.53 \\ Africa & 8053.8 & 8.43 \\ South Asia & 8760.8 & 9.17 \\ East and Central Asia & 21,168.6 & 22.17 \\ Southeast Asia & 1998.3 & 2.09 \\ Australia & 35,733.0 & 37.42 \\ Europe & 5080.4 & 5.32 \\ Totally & 95,483.2 & 100 \\ \hline \end{tabular}
\end{table} 
Table 1: Distribution of global saline–alkali areas.