Microbially induced calcite precipitation using Bacillus velezensis with guar gum

The present study was performed to explore the efficiency of microbially induced calcite precipitation (MICP) via locally isolated bacterial strains. Strains were isolated from soil and were screened for urease activity as well as microbial precipitation. Among all screened isolates, a carbonate precipitating soil bacterium was subjected for 16S rRNA gene sequencing. This strain was identified as Bacillus velezensis. The MICP characteristics of this strain were explored under three different media compositions and significant amount of precipitation in all cases was observed. Highest amount of precipitation was seen with guar as a biopolymer additive medium under experimented conditions. Activity of isolated strain with reference to pH profile, and ammonia concentration and total reducing sugar was further explored under media supplemented with four concentrations of guar (0.25%, 0.5%, 0.75% and 1% w/v). Microstructural analysis of microbial precipitation was performed with the help of scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) analysis, which confirmed the presence of calcium carbonate in different phases. The strain was subjected to bio-cementation and locally available sand was successfully consolidated. XRD results confirmed the presence of calcium carbonate on consolidated samples.