Abstract
Bacteria are capable of performing metabolic activities which thereby promote precipitation of calcium carbonate in the form of calcite. In this study, it is shown that microbial mineral precipitation was a result of metabolic activities of some specific microorganisms. Concrete microorganisms were used to improve the overall behavior of concrete. It was predicted that bacterial calcium carbonate (CaCO3) precipitation occurs as a byproduct of common metabolic processes such as urea hydrolysis. In this study, ureolytic bacteria that were capable of precipitating calcium carbonate were isolated and further their urease activity was tested based on the production of urease. Scanning electron microscopy (SED) analysis revealed the direct involvement of these isolates in calcium carbonate precipitation. The production of calcite was further confirmed by x-ray diffraction(XRD) and energy-dispersive x-ray (EDX) analysis. Key words: Bacteria, urease activity, microbial mineral precipitation, scanning electron microscope-energy-dispersive x-ray, x-ray diffraction.
Highlights
Bacteria are ubiquitous in every habitat on Earth, growing in soil, acidic hot springs, radioactive waste water and deep in the Earth's crust, as well as in organic matter and the live bodies of plants and animals
It is shown that microbial mineral precipitation was a result of metabolic activities of some specific microorganisms
It was predicted that bacterial calcium carbonate (CaCO3) precipitation occurs as a byproduct of common metabolic processes such as urea hydrolysis
Summary
Bacteria are ubiquitous in every habitat on Earth, growing in soil, acidic hot springs, radioactive waste water and deep in the Earth's crust, as well as in organic matter and the live bodies of plants and animals. Considerable research on carbonate precipitaton by bacteria has been done by using ureolytic bacteria These bacteria are able to influence the precipitaton of calcium carbonate by the production of urease enzyme. This enzyme catalyzes the hydrolysis of urea to co and ammonia, resulting in an increase of the pH and carbonate concentration in the bacterial environment (stocks et al, 1999). Microbial calcite precipitation (mcp) occurs as a by-product of common microbial metabolic process, such as urea hydrolysis, photosynthesis, sulfate reduction. These different metabolic processes increase the alkalinity (pH and dissolved inorganic carbon) and thereby favouring the calcium carbonate precipitation (Knorre and Krumbein, 2000).
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