טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentLivne Achiya
SubjectBiomineralization in Fungi - Control Over
Morphology, polymorph and Templating
DepartmentDepartment of Materials Science and Engineering
Supervisor Professor Boaz Pokroy


Abstract

Biomineralization is a process where living organisms form minerals. It is a multidisciplinary field of research, at the interface of biology, chemistry, materials and engineering. Different organisms have the ability to modify mineral crystals and control the crystal growth. Control over crystal growth is a key to control over the bulk properties. Whether it is mechanical properties, optical properties or function as a catalyst, we can modify it by controlling the growth process.

Biomineralization takes place in fungi as well. Fungi is one of the five kingdoms in nature, they exist for more than 2.4 billion years. Up to date, about 100000 species are known out of approximately 5.1 million species. Fungi developed two main mechanisms to turn metals from the environment into biominerals. One is active, where the fungus extracts organic molecules that bind the metal ions and precipitate them. The second is passive, where biosorption of the metal ions on the cell wall happens, and the mineral grows over the fungi mycelium. The general name for fungi biominerals is secondary minerals. The secondary minerals usually begin as geological minerals, they get bioweathered by the fungi into metallic ions, and then precipitate by the fungi.

Fungi biomineralization contributes to geology, bioweathering rocks into soil and precipitating different kind of minerals. An interesting example of mineral associated with fungal source is the needle fiber calcite. Extraordinary calcite needles very high aspect ratio (up to 100). These needles were never grown in vitro, and the formation mechanism is still a riddle.

In this research we investigate the fungi abilities in biomineralization, and the benefits we can achieve from the materials science point of view. We proved that fungi influence the crystal growth and can act as templates for crystal growth in different methods. For the first time we documented the ability of fungi mycelium as template for different materials, whether it is chloro-hydroxy-apatite tubes or hopeite (Zn3(PO4)2*4H2O) cylinders. These results are only the tip of an iceberg, the fungi kingdom is huge and there is more to it than meets the eye. We showed the results of only 5 fungi and 7 metals: 5 million more fungi to go.

For the first time, we managed to grow needles from fungal source in vitro. We developed a method to grow hexagonal aragonite needles with high aspect ratio (up to 40), in a simple one step synthesis. This result helps to verify the fungal source of the needle fiber calcite, providing a strong piece of evidence for the necessity of fungi in the process.

Understanding better the way fungi interact with the minerals and control over their growth may reveal novel methods in crystal growth. This may bring a simple and cheap method to grow ceramic minerals with control in the micro- and even nano-scale.