RESUMO
AIMS: Microbial induced calcium carbonate precipitation (MICP) is one of the bio-cementation methods for improving granular soils. This study evaluate the feasibility of obtaining a bacterial solution with high optical density and urease activity by an inexpensive corn steep liquor (CSL) medium in non-sterile conditions in order to achieve sand improvement. METHODS AND RESULTS: Corn steep liquor media with different concentrations (different dilution rates) were prepared and, without any autoclaving (non-sterile conditions), different percentage of the inoculum solutions were added to them and incubated. Effect of inoculum solution percentage and CSL dilution rates on specifications of bacterial solution was evaluated. Urease activity and scanning electron microscope (SEM) and X-Ray Diffraction (XRD) were used to efficiency of CLS media in sand improvement. The considerable urease activity was measured as 5·7 mS cm-1 min-1 using nonsterile CLS. By using CYNU (CSL-Yeast extract-NH4Cl-Urea) bacterial solution, the urease activity of 5·5 mS cm-1 min-1 for the OD600 (optical density at 600 nm) of 1·88 and, consequently, specific urease activity of 2·93 mS cm-1 min-1 OD600 -1 was obtained. The highest unconfined compressive strength (811 kPa) was obtained for the CYNU. XRD revealed new calcite peaks next to the quartz peaks. CONCLUSIONS: Production of inexpensive bacterial solution using diluted CSL as the inexpensive, effective and powerful culture media for Sporosarcina pasteurii cultivation in nonsterile conditions, allows geotechnical and biotechnological engineers to use MICP technology more widely in land improvement and field-scale bio-cementation and bioremediation projects. SIGNIFICANCE AND IMPACT OF THE STUDY: Obtaining high urease activity of inexpensive microbial solution using diluted CSL as the culture medium in nonsterile conditions, as the unique results of this study, can be significant in the field of bioremediation studies using MICP.
