M.S. - Bioengineering

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    In situ crystallization of native poly(3-hydroxybutyrate) granules in varying environmental conditions
    ([Honolulu] : [University of Hawaii at Manoa], [December 2010], 2010-12) Porter, Michael Martin
    Poly(3-hydroxybutyrate) (PHB) is a microbial biopolyester that can be produced from renewable feedstocks as an eco-friendly bioplastic. PHB in vivo exists as amorphous, intracellular granules that contain a small amount of water and are surrounded by a membrane of lipids and proteins. The native granules undergo varying degrees of crystallization when subjected to changes in environment such as dehydration, temperature, pH, and other mild conditions. For the first time, the in situ crystallization of native PHB granules was monitored via ATR-FTIR. Empirical models describing the crystallization of PHB granules in different environments were developed from Avrami's equation. The extent of granule crystallization is governed by granule size, number of nucleation points, and spherulitic geometry. The primary stabilizing factors of amorphous PHB granules are water, membrane lipids and proteins. Removing any of these factors may induce partial crystallization of PHB, which toughens the granules against extensive molecule degradation and granule aggregation.
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    Evaluation of a microwire sensor functionalized for rapid detection of escherichia coli cells from liquid foods
    ([Honolulu] : [University of Hawaii at Manoa], [December 2011], 2011-12) Lu, Lin
    Nowadays, outbreaks of foodborne illness linked to pathogenic bacteria such as Escherichia coli have attracted increasing public attention. Traditional culture-based methods for pathogens identification are time-consuming and labor-intensive, raising the need for fast and sensitive detection techniques. Rapid detection method for E. coli performed by a functionalized microwire sensor was developed and evaluated in this work. A gold-tungsten microwire with a diameter of 25 μm was immobilized with anti-E. coli-antibodies on the surface and used to capture E. coli bacterial cells from cells suspension with dielectrophoretic force generated by an alternating current (AC) electric field at 20 Vpp and 3 MHz. Both fluorescence microscopy and electrochemical techniques were employed to see the amount of cells captured on the wire. Field emission scanning electron microscopy was used to visualize the cells. The detection limit was found to be about 5 CFU/ml with only target bacterial cells captured on the wire. The developed sensor demonstrated relative high sensitivity and specificity with fast detection rate, which shows a strong potential for the application in food industry.