Microbially induced calcite precipitation using Bacillus velezensis with guar gum

Abstract

Mineral precipitation via microbial activity is a well-known process with applications in various fields. This relevance of microbially induced calcite precipitation (MICP) has pushed researchers to explore various naturally occurring MICP capable bacterial strains. The present study was performed to explore the efficiency of microbially induced calcite precipitation (MICP) via locally isolated bacterial strains and role of guar gum, which is a naturally occurring polymer, on the MICP process. The strains were isolated from local soil and screened for urease activity Further, the urease positive strain was subjected to urea and calcium chloride based medium to investigate the efficacy of isolated strain for microbial induced precipitation. Among screened isolates, the soil bacterium that showed urease positive behaviour and precipitated calcium carbonate was subjected to 16S rRNA gene sequencing. This strain was identified as Bacillus velezensis. Guar gum-a natural polymer, was used as a sole carbon source to enhance the MICP process. It was observed that the isolated strain was able to breakdown the guar gum into simple sugars resulting in twofold increase in calcium carbonate precipitate. Major biochemical activities of isolated strain pertaining to MICP such as ammonium ion concentration, pH profiling, and total reducing sugar with time were explored under four different concentrations of guar gum (0.25%, 0.5%, 0.75% and 1% w/v). Maximum ammonium ion concentration (17.5 μg/ml) and increased pH was observed with 1% guar gum supplementation, which confirms augmented MICP activity of the bacterial strain. Microstructural analysis of microbial precipitation was performed using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques, which confirmed the presence of calcium carbonate in different phases. Further, XRD and SEM based studies corroborated that guar gum supplemented media showed significant increase in stable calcite phase as compared to media without guar gum supplementation. Significant diverse group of nitrogenous compounds were observed in guar gum supplemented medium when subjected to Gas Chromatography-Mass spectrometry (GC-MS) profiling.

Characterization of a Novel CaCO3-Forming Alkali-Tolerant Rhodococcus erythreus S26 as a Filling Agent for Repairing Concrete Cracks

“…No mineral crystals were observed in urease-negative E. coli . The shape and size of CaCO 3 crystals depend on the molecular properties of exopolysaccharides secreted by bacterial cells, as well as on the colony form [ 14 ]. Furthermore, spherical CaCO 3 crystals, vaterites, are primarily formed in solid medium containing agar [ 15 ].…”

Microbial induced calcite precipitation can consolidate martian and lunar regolith simulants

“…Our study shows a significant increase in the compressive strength of the resulting consolidated brick-like structures with both martian and lunar regolith simulants. The present work also utilizes a naturally occurring and economically viable bio-polymer guar gum, to further improve the strength of these bio-consolidated ‘space bricks.’ Guar gum acts as a binder [ 30 , 44 ] with soil for improving mechanical strength, and is also stable with pH/temperature variation [ 45 , 46 ] thus making it an ideal additive for MICP mediated space brick formation. For our work, we used the microbe Sporosarcina pasteurii —a much explored MICP capable bacteria and a gram positive non-pathogenic strain [ 33 , 47 – 49 ].…”

Preferential Adsorption of Prominent Amino Acids in the Urease Enzyme of Sporosarcina pasteurii on Arid Soil Components: A Periodic DFT Study

“…1,5,6,9,10 Due to its widespread and soil-borne nature, the urease enzyme as produced by the S. pasteurii bacterium is a popular choice for use in soil strengthening. 11 In MICP, the microbes secrete the urease enzyme which then catalyzes the production of calcite. The produced calcite builds up around the microbes, eventually encapsulating them and killing them via deprivation of nutrients.…”