In recent years, the interest in obtaining microbial cement has gained its popularity along with such problems as fractures and fissures in concrete structures which is created by weathering, land subsidence, faults, earthquakes and human activities. Synthetic biology has proposed a novel way to repair and remediate problems.

One of the possible solution is biomineralization of calcium carbonate using microbes such as Bacillus species. The application of microbial concrete in construction may simplify some of the existing construction processes and revolutionize them.

Back to basics

Biomineralization is a natural process in living organism by which they are able to produce minerals. Production of microbial calcium carbonate (CaCO3) is a widely studied and a promising technology with many uses in various engineering applications, for example: treatment of concrete,construction materials such as building bricks and as fillers for rubber, plastics and ink.

There are three distinct pathways of bacterial calcium carbonate precipitation:

1) biologically controlled - cellular specific control of formation of the mineral (exoskeleton, bone or teeth),

2) biologically - influenced - passive mineral precipitation caused through the presence on the surface of the cell of organic matter and

3) biologically- induced - which is the chemical alteration of an environment by biological activity.

The most commonly found mechanism in bacteria for calcite precipitation has been to generate an alkaline environment through different physiological actions. Precipitation of carbonates via urea hydrolysis by ureolytic bacteria is the most straightforward and most easily controlled mechanism of microbially induced calcium carbonate precipitation with the potential to produce high amounts of carbonates in short period of time.

Alternative

Instead of calcite precipitation from natural microbes, many other organisms also have the power to produce calcium carbonate, such as corals. In the stony coral, Stylophora pistillata, 4 acid-rich proteins (CARPs 1–4; GenBank accession numbers KC148537–KC148539 and KC493647) were identified to be responsible for calcium carbonate precipitation. These proteins were found in the study of changes in the growth of corals with increasing of acidity in the ocean.

As such, bioreaction of aragonite formation is far from the thermodynamic equilibrium. It may even compromise with acidification and very low mineral saturation state (E. Tambutté & A. A. Venn et al. 2015). All CARP 1-4 can be cloned and expressed in E.coli BL21 strain and remain the activity. Each of them is able to independently catalyze the calcification in artificial seawater. This method we decided to use and improve in our project/ due to the our project.

Silicate (Si_mO_n) is one of the known form of biomineralization, the main component of planet’s crust, and many synthetic materials . The physical properties depend entirely on how the silica crystals are organized, quartz, glass or others. Its formation processes in sponge and diatom are fairly well known. The pathways require multiple proteins, but the key factors have been successfully expressed in E.coli. This silicatein gene come from the sponge Suberites domuncula. Silicatein has been documented in different works in vivo.

Centre for Research and Interdisciplinarity (CRI)
Faculty of Medicine Cochin Port-Royal, South wing, 2nd floor
Paris Descartes University
24, rue du Faubourg Saint Jacques
75014 Paris, France

bettencourt.igem2017@gmail.com

Team:Paris Bettencourt/Biomaterials

Back to basics

Alternative