Optimization of growth conditions and biological cementation effect of Sporosarcina pasteurii

Microbially induced carbonate precipitation (MICP) has been widely used in soil reinforcement and other fields. Aiming at the problems of accumulation and resource utilization of tailings sand, which is a special kind of sand, we enriched the urease-producing microorganism Sporosarcina pasteurii (S. pasteurii) from soil and applied it to the field of tailings solidification in this study. Based on single-factor experiments and response surface methodology (RSM), the effects of temperature, pH and urea concentration on the growth of S. pasteurii were investigated and the optimum growth conditions of S. pasteurii were determined. CaCl2·2H2O and Ca(CH3COO)2·H2O were used as calcium sources, combined with SEM-EDS, XRD, FTIR and XPS detection, the effect and mechanism of Ca2+ bio-cementation by S. pasteurii was investigated. By comparing the effect of bio-cemented tailings sand by soaking method, stirring method and stratification method, we optimized the method of S. pasteurii bio-cemented tailings. The results indicated that the activity of S. pasteurii mixed bacteria enriched in soil was significantly better than that of single S. pasteurii standard strain. In particular, the S. pasteurii mixed bacteria (1# bacteria) enriched from the soil around the pig manure pile had the strongest activity. The results of RSM showed that the optimum growth conditions of 1# bacteria were: at 31°C culturing temperature, pH = 9.07, which urea concentration was 0.5 mol/L. Compared with temperature and pH value, urea concentration had the most obvious effect on the activity of 1# bacteria. Compared with the soaking method and the stirring method, the layered solidification method using Ca(CH3COO)2·H2O as the bio-cemented calcium source was more suitable for S. pasteurii mixed bacteria (1# bacteria) enriched from soil bio-cementing tailings. This bio-cementing technology provides a theoretical basis for the efficient MICP engineering application of tailings in the field of alternative building materials.