M.S. - Bioengineering

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

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Design, Simulation And Fabrication Of A Cooler And Controller Facilitating Study Of Magnetic Field Effects On Nucleation In Super Cooled Bulk Water
(University of Hawaii at Manoa, 2020) Francis, Sean; Jun, Soojin; Biological Engineering
In this paper the effects of magnetic fields on supercooled water were investigated for application to a food supercooling storage technology that uses magnetic fields. Current cold storage technologies were reviewed and compared to supercooled storage, highlighting the latter’s longer storage periods without changing food texture. Literature on supercooled water was also reviewed, featuring crossover and relaxation phenomena definitions used in waters possible “liquid-liquid” critical point. Using equations from a previous Monte Carlo study, a correlation between magnetic fields and waters temperature was proposed, showing the magnetic moment between two water molecules in a given magnetic field will decrease with temperature. Furthermore, it was shown that the magnetic moment interaction between water molecules and a 0.6 T magnetic fields imparted ~-2.3*〖10〗^(-5) J/mol energies at -10°C. With this model as a guideline, a cooling device (Supercooler 2) and controller were created to investigate supercooled waters interaction with magnetic fields. Energy balance calculations were used to define hardware specifications before creating a CAD model. Computational fluid dynamic (CFD) analysis on the model showed thermal gradients were minimized when simultaneously drawing heat from the top and bottom of the sample, validating this design feature. The main chassis and custom designed integral components were 3D printed from the CAD and assembled with a GMW 3470 electromagnet to create Supercooler 2 (Appendix F). The Supercooler 2 performance validation testing showed the sample gradient was 0.6°C when cooled bi-directionally and 1.19°C unidirectionally. Further analysis fitted a linear model to sample cooling rates where R^2=0.995 could be obtained with 95% prediction interval=±0.33 °C for 5 repeated replicates, demonstrating the linear temperature control accuracy and precision. A preliminary study using 20 samples with pulsed magnetic fields from 1-100 Hz and 10-600 mT had a normally distributed nucleation temperature with mean= -7.39 and standard deviation=0.307°C. Linear regression models were fit to the results, showing positive correlation between increasing frequencies and supercooling magnitude. Negative correlation was shown between increasing field strength and supercooling magnitude. The independent variables, magnetic frequency and magnitude, were changed simultaneously and thus correlation with supercooling magnitude was ambiguous. This experimental method saved time and provided background data. Furthermore, outliers were discovered and the data provided by this study highlighted a group treated with 70 mT at 20 Hz. This group’s nucleation temperatures were 2.11 standard deviations away from the mean, while the average for the remaining dataset was 0.739, and therefore, it is suggested that the group be investigated for future studies. The subsequent High Field Study improved upon critical experimental methods and process controls. This study focused on experimental groups treated with 600 mT 1 Hz fields and Control groups with no treatment. In the midst of the High Field Study, the PID process variable location was changed to improve smoothness of the sample temperature cooling profile. The result was a separation of groups; two Control groups and two Experimental groups. All groups were found to have the same cooling rates and steady state temperatures. This was shown with 95% prediction intervals=±0.68°C and ±0.82°C for steady state and linear cooling regimes, respectively. This included 16 Control groups (no magnetic field treatment) and 13 Experimental groups treated with 600 mT 1 Hz fields. Experimental groups were 1.5 to 2.9 times more likely to have a nucleation event than Control groups. The temperature profiles were statistically the same between all groups, therefore, the only remaining variable was the difference in treatment. Therefore, the Experimental groups had an increased nucleation probability compared to the control group because of the 600 mT 1 Hz treatment.
Design, Fabrication, and Validation of a Microcontroller Based Supercooling Control Unit for Use in Food Preservation
(University of Hawaii at Manoa, 2017-12) Hoptowit, Raymond A.; Biological Engineering
Freezing is the most widely used food preservation technique in the commercial and domestic market, however the freezing process causes irreversible damages to foods as ice nucleation occurs. New emerging technologies attempt to prevent these damages from occurring by delaying ice formation within foods while maintaining internal sub-zero temperatures (i.e., Supercooling). Investigations into the simultaneous application of pulsating electric fields (PEF) and oscillating magnetic fields (OMF) during the freezing process for extension of the supercooled state within foods have been conducted. In such studies it is common to use numerous electrical equipment and instruments to precisely measure and regulate the power applied to the test food during the supercooling process. As a result, these studies have proven to be quite expensive. In an effort to reduce costs, improve portability, and simplify the data collection process a supercooling control unit was developed to replace all major equipment related to supercooling research conducted at the University of Hawai‘i at Mānoa (Hawaii, USA). The control unit regulates and monitors all power within the magnetic and electric field generation systems. A separate thermocouple based temperature measurement system allows for monitoring of any temperatures associated with the test food sample or ambient environments. Data logging is accomplished either through on-board SD™ card or through USB port to external PC. The supercooling control unit offers a total uncertainty of ±0.7˚C for temperature measurements, ±1.71% of measurements for the PEF current, ±1.67% of measurements for PEF voltage, ±2.88% of measurements for OMF current, and ±1.91% of measurements for OMF voltage. Supercooling experiments conducted with the newly developed control unit have shown agreeable measurements with lab grade electrical equipment. 180g top round beef steak (London broil) was successfully supercooled at -4˚C for a validation period of 7 days, various food quality assessments conducted on the beef showed comparable results with data from previous supercooling studies. The control unit provides a seamless data collection process, while maintaining an adequate level of precision and accuracy within collected data. The newly developed device cuts costs, improved portability, and offers a scale-able platform upon which additional functionality can be implemented.
Protein-Rich Fungal Biomass Cultivation on Agro-Industrial Wastes/Residues for Aquaculture Feed Production with Simultaneous Organic Removal
(University of Hawaii at Manoa, 2017-12) Batsaikhan, Misheel; Biological Engineering
Global aquaculture industry faces an ever increasing challenges of acquiring feed that is cost efficient yet environmentally sustainable. Single cell protein (SCP) from the edible fungus R.oligosporus has high potential as aquaculture feed as it is nonpathogenic to humans and has high essential amino acid and fatty acid content for fish feed. Additionally, to minimize cost and promote sustainable development, fungal protein can be cultivated on low-cost wastes/residues, preferably from agricultural industries which are high in organics and nutrients. In this research, fungal biomass was investigated for its ability to grow on variety of agro-industrial wastes/residues. Sugarcane molasses, unmarketable papaya juice, and sugarcane vinasse were examined for their potential as substrates. Efficiency of organics removal, quantified as soluble chemical oxygen demand (sCOD) was also examined to determine feasibility of the process as a bioremediation technology. Small scale optimization studies showed that the fungus can successfully be cultivated on all three of the agro-industrial wastes/residues. Molasses, however, yielded the highest specific fungal biomass of 0.41 ± 0.02 (g biomass/g sCOD removed) at COD concentration of 50 g/L, and pH of 5.0. Both molasses and vinasse achieved fungal pellet growth, while papaya juice only supported free mycelial growth. Sugarcane molasses was selected for the bench-scale studies to further demonstrate the feasibility of the bioremediation process. Fungal fermentation was conducted in two 2.5-L working volume bubble column reactors. Maximum fungal biomass yield of 4 grams of dry biomass per liter of molasses was achieved after 48 hours of cultivation. Organics removal of 56 ± 4.23 % (quantified as % sCOD removed) as well as significant solids and nutrients removal were also obtained. However, bacterial contamination was detected beginning at 16 hours post spore inoculation, and may have assisted the organics and nutrient removal. Molasses-derived fungal biomass had a protein content (38%), essential fatty acid profile and in vitro protein digestibility (~80%) comparable to that of commercial fish feed. Importantly, lysine, a limiting amino acid in fish feed, was in high amount (8.6%).
In situ crystallization of native poly(3-hydroxybutyrate) granules in varying environmental conditions
(University of Hawaii at Manoa, 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.
Evaluation of a microwire sensor functionalized for rapid detection of escherichia coli cells from liquid foods
(University of Hawaii at Manoa, 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.
Pulsed field electroflotation for harvesting microalgae
(University of Hawaii at Manoa, 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.
Yeast from papaya processing wastes as aquaculture feed supplement
(University of Hawaii at Manoa, 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.
Comparison of different technologies for dilute milk parlor wastewater treatment and reuse
(University of Hawaii at Manoa, 2007) Lin, Luo-Ting
Analysis of segmentation methods for partial volume correction in magnetic resonance spectroscopy voxels
(University of Hawaii at Manoa, 2007) Andrews-Shigaki, Brian C.
Application of EMMC-biobarrel technology for domestic wastewater treatment and reuse
(University of Hawaii at Manoa, 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.

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