In vitro synthesis of bio-brick using locally isolated marine ureolytic bacteria, a comparison with natural calcareous rock

Abstract

Microbially Induced Calcite Precipitation (MICP) using ureolytic bacteria has emerged as a promising technology with several applications in geotechnical engineering. In the current study, bacterial isolates from marine environment (coastal sandstones) have been investigated for their calcification potential. The isolated ureolytic bacterial strains NIOT-1 exhibited high urease activity and identified as Sporsarcina pausterii, were selected for further studies. The laboratory tests revealed that Sporsarcina pausterii NIOT-1 precipitated calcite crystals between the sand particles through the enzymatic hydrolysis of urea, which increased the ammonium concentration to the maximum of 366.54 mM and pH of 8.32. The petrological analysis of the samples indicated that the dominant carbonate phase was calcite. This precipitation of calcite crystals between the sand particles resulted in the physical stabilization of sand leading to the unconfined compressive strength to 3950 kpa. The strength of the laboratory made calcareous sandstone was comparatively higher when compared with the naturally formed calcareous sand rocks (3100 kpa (Uvari) and 1000 kpa (Pudumadam)) along the coasts, but the naturally formed ferrugineous sandstone belongs to Vepalodai was higher compared to all (30500 kpa). This has been envisaged by adopting MICP techniques in preventing the beach sand movement to protect eroding shoreline and to protect coastal populace at critical pockets of the coast as a nonconventional coastal protection measure.