/pdf/processes-of-carbonate-precipitation-in-modern-microbial-176vfhaypi.pdf

Processes of carbonate precipitation in modern microbial mats

Microbial carbonate precipitation in construction materials: A review

Microbially induced calcium carbonate precipitation (MICCP) is a naturally occurring biological process in which microbes produce inorganic materials as part of their basic metabolic activities. This technology has been widely explored and promising with potential in various technical applications. In the present review, the detailed mechanism of production of calcium carbonate biominerals via ureolytic bacteria has been discussed along with role of bacteria and the sectors where these biominerals are being used. The review discusses the applications of bacterially produced carbonate biominerals for improving the durability of buildings, remediation of environment (water and soil), sequestration of atmospheric CO2, filler material in rubbers and plastics etc. The study also sheds light on benefits of bacterial biominerals over traditional agents and also the issues that lie in the path of successful commercialization of the technology of Microbially induced calcium carbonate precipitation from lab to field scale.

/pdf/biomineralization-of-calcium-carbonates-and-their-engineered-elsofi30be.pdf

Biomineralization of calcium carbonates and their engineered applications: a review

Calcium carbonate represents a large portion of carbon reservoir and is used commercially for a variety of applications. Microbial carbonate precipitation (MCP), a by-product of microbial activities, plays an important metal coprecipitation and cementation role in natural systems. This natural process occurring in various geological settings can be mimicked and used for a number of biotechnology such as metal remediation, carbon sequestration, enhanced oil recovery and construction restoration. In this study, different metabolic activities leading to calcium carbonate precipitation, their native environment, and potential applications and challenges are reviewed.

/pdf/carbonate-precipitation-through-microbial-activities-in-44nuyja0gg.pdf

Carbonate Precipitation through Microbial Activities in Natural Environment, and Their Potential in Biotechnology: A Review

Biomineralization is a naturally occurring process in living organisms. In this review, we discuss microbially induced calcium carbonate precipitation (MICP) in detail. In the MICP process, urease plays a major role in urea hydrolysis by a wide variety of microorganisms capable of producing high levels of urease. We also elaborate on the different polymorphs and the role of calcium in the formation of calcite crystal structures using various calcium sources. Additionally, the environmental factors affecting the production of urease and carbonate precipitation are discussed. This MICP is a promising, eco-friendly alternative approach to conventional and current remediation technologies to solve environmental problems in multidisciplinary fields. Multiple applications of MICP such as removal of heavy metals and radionuclides, improve the quality of construction materials and sequestration of atmospheric CO2 are discussed. In addition, we discuss other applications such as removal of calcium ions, PCBs and use of filler in rubber and plastics and fluorescent particles in stationary ink and stationary markers. MICP technology has become an efficient aspect of multidisciplinary fields. This report not only highlights the major strengths of MICP, but also discusses the limitations to application of this technology on a commercial scale.

/pdf/formations-of-calcium-carbonate-minerals-by-bacteria-and-its-4nmpad9p6x.pdf

Formations of calcium carbonate minerals by bacteria and its multiple applications.

It is thought that morphologies of bacterial carbonates can be used to identify microbial fossils and/or precipitates in sediments and rocks. This study shows that calcite and vaterite formed in a gel medium in the presence of Myxococcus xanthus display a range of morphologies that depend on whether the bacteria are live or dead. Metabolic activity of the bacteria induced: (1) aggregates of calcified bacteria formed at maximum supersaturation; (2) vaterite spheres (final growth stage of dumbbell fibrous-radiated aggregates); and (3) dipyramid- and disphenoid-like calcite crystals (combination of {011} and {0001} forms). Morphologies (2) and (3) developed at a lower supersaturation and are typically found in gel-like media. Dipyrimidal-like calcite crystals were also obtained abiotically in gel medium. Dead M. xanthus cells induced heterogeneous precipitation of calcite with rhombohedral morphologies at low supersaturation. A growth mechanism resulting from self-assembly of calcium carbonate nanocrystals may account for the observed morphologies, crystal microstructure, and crystallite size measurements. All of the above-mentioned morphologies of bacterial carbonate have been observed in other laboratory experiments and in continental and marine environments. However, all of them have also been produced abiotically, with the exception of calcified bacterial cells. This may make it more difficult to identify bacterial activity in the rock record. Nonetheless, bacterially induced alkalinization appears to be a prerequisite for the development of spherulitic and dipyramid- or disphenoid-like forms in natural mucilaginous biofilms and microbial mats. The morphologies reported here may facilitate the recognition of early and recent marine and continental microcrystalline bacterial carbonates and cements.

Guiseppe Cultrone

Papers

Precipitation and Growth Morphology of Calcium Carbonate Induced by Myxococcus Xanthus: Implications for Recognition of Bacterial Carbonates