M.S. - Bioengineering

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https://hdl.handle.net/10125/1918

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Now showing 1 - 10 of 21
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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.
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    Pulsed field electroflotation for harvesting microalgae
    ([Honolulu] : [University of Hawaii at Manoa], [May 2014], 2014-05) Koelsch, Kyle Malone
    Microalgae are used in a number of commercial applications including biofuel production, nutraceuticals, and as feedstock for aquaculture. Typical methods for harvesting microalgae like centrifugation, microfiltration, and foam fractionation are extremely energy intensive. Reducing the energy input for harvesting microalgae would improve the overall energy balance for algae based biofuels and benefit any industry where algae is required. One method for harvesting microalgae is electrolytic flotation (electroflotation). This is simply using electrolysis-generated bubbles to float particles out of suspension and to the surface. The primary objective of this research project is to examine the effects that electrical waveform characteristics have on bubble size, gas generation efficiency, biomass separation, and lipid separation of Chlorella sp. from a marine media. Sets of 23 factorial tests were performed on a coplanar interdigitated electrode array. The waveform variables reviewed included applied potential, duty cycle, and frequency. The smallest mean bubble diameter (30.1 μm) occurred at 3V, 20%, 25 Hz. The smallest median bubble diameter (25.0 μm) occurred at 3 V, 10%, 25 Hz. The highest observed gas generation efficiency (1.69x10-6 (mol J-1)) occurred at 3 V DC. The highest observed biomass recovery (6.8%) occurred at 6 V, 20%, 25 Hz. Lipid recovery analysis was attempted as well but high variability in results rendered it inconclusive.
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    Yeast from papaya processing wastes as aquaculture feed supplement
    ( 2007) Kang, Hsu-Ya
    The Pacific Island is facing the challenge of short in cost-effective aquafeed. The protein source is the most costly ingredient in feed supplements. Yeast is enriched with protein and has been reported to be able to enhance shrimp's immune system, survival rate and average body weight. Hawaii produces million tons of fruit and food by-products each year which may have the potential to be upgraded into protein enriched value-added products. This study plans to develop a bioprocess procedure to convert fruit processing wastes into yeast biomass, to establish design and operational criteria for yeast production in batch and/or continuous/semi-continuous flow system, to evaluate the nutrient potential of the bioprocessed product as shrimp feed and the cost of the proposed production system. Papaya processing waste collected from a food company in Honolulu was used for yeast growth (S. cerevisiae) in a 14-L fermenter mixing at 200 rpm under room temperature (22±2°C). PH, oxidation reduction potential (ORP) and dissolved oxygen (DO) were monitored with the change of soluble chemical oxygen demand (SCOD) removal and suspended solids increase in the growth medium to determine the required reaction time for maximum desirable product formation. An initial SCOD concentration ranged from 12,000 to 25,000 mg/l with 8-12h aeration was found for optimal and economical operation in the batch production system. It was able to remove more than 70% SCOD and produce 40-45% crude protein in suspended solid. Preliminary work of continuous/semi-continuous flow operation, shrimp (L. vannamei) feed trail and economic analysis on the batch production system indicated the successful development of the bioprocess system would be a mutual beneficial solution for local aqua-industries and environmental pollution control. In addition, the bioprocess could be applied widely to other agri-food by-products to produce the value-added products for the sustainability of agriculture production and environmental protection.
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    Application of EMMC-biobarrel technology for domestic wastewater treatment and reuse
    ( 2006) Zhu, Jia, 1977
    The entrapped-mixed-microbial-cell-biobarrel (EMMC-biobarrel) processes with both configurations of single-layer and double-layer were investigated for the removal of carbon and nitrogen simultaneously from synthetic-domestic wastewater with a CODIN ratio of 5 under various operational conditions. For the single-layer systems, the carrier was employed at the packing ratios of 10% and 20% based on the bioreactor water volume. In the double-layer system, carriers were separated into two layers which occupied the top and bottom parts of the reactor with an overall packing ratio of 13%. At the organic and nitrogen loading of O.75kg COD/m3/day and 0.16kg NH3-N/m3/day, all these systems achieved more than 96% of SCOD removal and NH3-N removal efficiencies under continuous aeration. The double-layer system achieved about 40% of total nitrogen removal, which was comparable with the single-layer system with packing ratio of 20% but higher than the single-layer system with a packing ratio of 10%. The SRT for the double-layer system and single-layer system with a packing ratio of 20% could be achieved to more than 200 days. Based on the economics analysis, in the achievement of comparable performance, the capital cost for the double-layer configuration was lower than that for the single-layer configuration. Therefore, double layer configuration is recommended for the EMMC-biobarrel process design. EMMC-biobarrel process offers many advantages over the existing wastewater treatment processes including small space requirement, simple operation and maintenance and . improved nitrogen removal. It demonstrates great potential for onsite, small scale/land limited wastewater treatment applications. The installation cost for an EMMC-biobarrel treatment unit with capacity of 400 gallons/day and 1,500 gallons/day are estimated as $4,671 and $10,191, respectively, which are comparable or lower than those for the existing commercial products which also involve the nitrogen removal technology. For small sca1e/land limited application, the total cost requirement is about $0.90 per 1000 gallons for treating settled domestic sewage per day.