Graduate Thesis Or Dissertation


Studies of Chitin Nanofiber Production and Photoluminescent Biosilica from Diatoms with and without Germanium Public Deposited

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  • There is significant interest in harnessing the biosynthetic capacities of photosynthetic diatom microalgae for the production of unique bioinspired nanomaterials. Specifically, this research focuses on understanding the photoluminescent properties of diatom biosilica and β-chitin nanofiber production in diatoms. Diatoms are single-celled microalgae that possess intricately patterned biosilica shells called, frustules. They require silicon for cell wall biosynthesis and subsequent cell division, and as a result silicon availability can be used to manipulate the cell cycle. Photoluminescence emission of diatom biosilica in living diatom cells emerged once all dissolved silicon was consumed, with two primary peaks centered at 500-510 nm and 680 nm, attributed to the diatom biosilica and chlorophyll autofluorescence respectively. Additionally, chitin nanofiber production is directly tied to cell division, which is controlled by silicon availability. The extracellular formation of β-chitin nanofibers by the centric diatom Cyclotella sp. was followed during batch cultivation at low (0.25 mM) and high (1.7 mM) initial silicon loadings. Chitin nanofibers are excreted as an individual fiber of nominal 50 nm diameter and 60 μm length through specialized ports called, fultoportulae (20 per valve, 40 per cell), that line the rim of the diatom valve. Like photoluminescence, chitin production primarily occurred once a state of silicon limitation was reached in suspension. Furthermore, using a two-stage batch process for the co-feeding of dissolved silicon and germanium to a silicon starved suspension generated diatom cells with metabolically incorporated germanium in its frustule. Germanium incorporation had no effect on chitin yield per cell. This study demonstrates the ability of diatoms to produce a variety of co-products that may be useful for next generation advanced materials.
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