Optimization of Urease Production Capacity of a Novel Salt-Tolerant Staphylococcus xylosus Strain through Response Surface Modeling

Encouraging advances have been made in the application of microbial mineralization towards fixing and improving desertified sandy soils. However, desert soils in arid areas exhibit high salinity that may limit urease activity and production in microbial strains, thereby affecting the solidification effects of microbial calcium binders in saline soils. In this study, a salt-tolerant microbial strain (A80) that produced urease was identified from saline soils of the Qaidam Basin. The culture conditions of the strain were optimized using single-factor tests and response surface methods to optimize urease yields and activity. The optimal composition of the A80 medium included an inoculation amount of 6.32% (V/V), a yeast extract powder concentration of 15.43 g/L, a glucose concentration of 5.20 g/L, a salinity of 3%, and an incubation temperature of 36 °C. Urease activity increased by 64.80% after using optimized medium. The A80 microbial calcium-cementing agent was also used to solidify saline soils, leading to an increased unconfined compressive strength of the solidified saline soil by 25.70%. Thus, the optimization method resulted in improvements in the cultivation of a salt-tolerant strain.