Abstract:
Ureases represent a class of enzymes responsible for the hydrolysis of urea, leading to the production of ammonia and carbon dioxide. Within the construction sector, urease-producing bacteria have demonstrated their significance in facilitating microbially induced calcium carbonate precipitation. This research centers on the characterization of bacterial strains isolated from cement for the purpose of enhancing concrete properties. Two distinct bacterial isolates, designated as CA (B) and CA (F), were obtained from cement samples using an enrichment culture technique. Assessment of these isolates confirmed their capability for urease production. Enzyme activity analyses were conducted, revealing that isolate CA (F) displayed an average enzyme activity of 0.0005 mg/mM/s, while isolate CA (B) exhibited 0.0002 mg/mM/s. The optimal substrate concentration for urease activity was determined to be 1mM for isolate CA (F) and 3mM for isolate CA (B). Furthermore, the most favorable temperature for urease activity was found to be 50℃ for isolate CA (F) and 70℃ for isolate CA (B), with both isolates displaying an optimum pH of 9.5. Through a combination of cultural, biochemical, and molecular assessments, isolate CA (F) was identified as Lysinibacillus fusiformis strain 5B. Its notably heightened enzyme activity rendered it suitable for large-scale urease production, which was subsequently harnessed in the fabrication of bio-concrete. This study also encompassed the production of control concrete without urease. The resultant concrete cubes underwent curing for durations of 7, 14, and 28 days, followed by assessment of compressive strength. The concrete treated with urease exhibited remarkable compressive strength values on days 7, 14, and 28, with mean values of 24.71, 27.55, and 28.14 N/mm², respectively. The control concrete also demonstrated substantial compressive strength values of 20.46, 23.11, and 22.53 N/mm², surpassing the International Standard comprehensive strength benchmarks for grade 25 concrete, set at 16.25, 22.50, and 24.75 N/mm². Scanning electron micrographs unveiled visible deposits of calcium carbonate crystals on the surface of urease-treated concrete, while the control concrete exhibited no discernible crystals. Collectively, the outcomes of this investigation underscore the capacity of urease produced by Lysinibacillus fusiformis strain 5B to augment concrete strength.
EVALUATING THE CHARACTERISTICS OF BACTERIAL UREASE ISOLATES FROM CEMENT FOR CONCRETE ENHANCEMENT, GET MORE, ACTUARIAL SCIENCE PROJECT TOPICS AND MATERIALS
