Matching Items (12)
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- All Subjects: E. coli
- Creators: Chemical Engineering Program
Description
Depletion of fossil fuel resources has led to the investigation of alternate feedstocks for and methods of chemical synthesis, in particular the use of E. coli biocatalysts to produce fine commodity chemicals from renewable glucose sources. Production of phenol, 2-phenylethanol, and styrene was investigated, in particular the limitation in yield and accumulation that results from high product toxicity. This paper examines two methods of product toxicity mitigation: the use of efflux pumps and the separation of pathways which produce less toxic intermediates. A library of 43 efflux pumps from various organisms were screened for their potential to confer resistance to phenol, 2-phenylethanol, and styrene on an E. coli host. A pump sourced from P. putida was found to allow for increased host growth in the presence of styrene as compared to a cell with no efflux pump. The separation of styrene producing pathway was also investigated. Cells capable of performing the first and latter halves of the synthesis were allowed to grow separately and later combined in order to capitalize on the relatively lower toxicity of the intermediate, trans-cinnamate. The styrene production and yield from this separated set of cultures was compared to that resulting from the growth of cells containing the full set of styrene synthesis genes. Results from this experiment were inconclusive.
ContributorsLallmamode, Noor Atiya Jabeen (Author) / Nielsen, David (Thesis director) / Cadillo-Quiroz, Hinsby (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor) / School of Life Sciences (Contributor)
Created2015-05
Description
The goals of the styrene oxide adsorption experiments were to develop reliable isotherms of styrene oxide onto Dowex Optipore L-493 resin and onto mesoporous carbon adsorbents, in addition to determining the ideal conditions for styrene oxide production from E. coli. Adsorption is an effective means of separation used in industry to separate compounds, often organics from air and water. Styrene oxide adsorption runs without E. coli were conducted at concentrations ranging from 0.15 to 3.00 g/L with resin masses ranging from 0.1 to 0.5 g of Dowex Optipore L-493 and 0.5 to 0.75 g of mesoporous carbon adsorbent. Runs were conducted on a shake plate operating at 80 rpm for 24 hours at ambient temperature. Isotherms were developed from the results and then adsorption experiments with E. coli and L-493 were performed. Runs were conducted at glucose concentrations ranging from 20-40 g/L and resin masses of 0.100 g to 0.800 g. Samples were incubated for 72 hours and styrene oxide production was measured using an HPLC device. Specific loading values reached up to 0.356 g/g for runs without E. coli and nearly 0.003 g of styrene oxide was adsorbed by L-493 during runs with E. coli. Styrene oxide production was most effective at low resin masses and medium glucose concentrations when produced by E. coli.
ContributorsHsu, Joshua (Co-author) / Oremland, Zachary (Co-author) / Nielsen, David (Thesis director) / Staggs, Kyle (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor) / School of Sustainability (Contributor)
Created2014-05
Description
The demographics of Arizona are changing as Hispanics children are passing through their youth and into adulthood. Yet, even with this changing population Arizona has demonstrated an unwillingness to provide adequate educational opportunities for Hispanic school children. The state has perpetuated fear throughout the Hispanic community in an attempt to marginalize and stigmatize the race. Such attempts have extended to youth in schools creating an environment of fear. This fear limits the academic potential of young Hispanics who are wary of government officials and institutions. Arizona has also failed to provide appropriate funding for programs used predominantly by Hispanic students leaving them unprepared for a workplace that desperately needs them. Finally, Arizona has refused to allow course content with a record of increasing academic achievement and graduation rates amongst Hispanics to be taught in schools. Taken as a whole Arizona's efforts are creating a cadre of unskilled and unprepared laborers who will be desperately needed to take jobs in the Arizona economy in the coming years. This blatant disregard for the educational needs of a large segment of the population will have a devastating impact on Arizona's future.
ContributorsSmith, Jason Ryan (Author) / Davis, T. J. (Thesis director) / Ovando, Carlos (Committee member) / Tsosie, Rebecca (Committee member) / Barrett, The Honors College (Contributor) / School of Historical, Philosophical and Religious Studies (Contributor)
Created2013-12
Description
Contributing to the small but growing body of research on linguistic discrimination in legal settings, this thesis conducts a sociolinguistic investigation of the impact of an individual's accent on juror perceptions of defendant favorability and innocence. The study used an online questionnaire in which sixty mock jurors were each asked to evaluate the audio testimony of a defendant representing one of three English ethnolects: African American, British South African, or Caucasian American. In addition to rating the defendant's persuasiveness, honesty, credibility, trustworthiness, and guilt, participants were also asked to determine an appropriate punishment (if any) for the defendant. Results indicate a preference of participants to issue an unsure or caveat opinion for the African American speaker but not to the British South African or Caucasian American speaker. The implications of these findings, as well as the correlations between each variable are discussed. The paper concludes with a recommendation for legal training and a revision of courtroom practices.
ContributorsMaerowitz, Max Robert (Author) / Prior, Matthew (Thesis director) / Adams, Karen (Committee member) / Barrett, The Honors College (Contributor) / School of Historical, Philosophical and Religious Studies (Contributor) / Department of English (Contributor)
Created2014-05
Description
The aim of this thesis is to explore the relationship between architecture and history in Virginia from 1607 to the eve of the American Revolution to create a complete historical narrative. The interdependency of history and architecture creates culturally important pieces and projects the colonist's need to connect to the past as well as their innovations in their own cultural exploration. The thesis examines the living conditions of the colonists that formed Jamestown, and describes the architectural achievements and the historical events that were taking place at the time. After Jamestown, the paper moves on to the innovations of early Virginian architecture from Colonial architecture to Georgian architecture found in Williamsburg. Conclusively, the thesis presents a historical narrative on how architecture displays a collection of ideals from the Virginian colonists at the time. The external display of architecture parallels the events as well as the economic conditions of Virginia, creating a social dialogue between the gentry and the common class in the colony of Virginia.
ContributorsChang, Hosu (Author) / Gray, Susan (Thesis director) / O'Donnell, Catherine (Committee member) / Barrett, The Honors College (Contributor) / School of Historical, Philosophical and Religious Studies (Contributor) / School of Social Transformation (Contributor)
Created2015-05
Description
The inability of a single strain of bacteria to simultaneously and completely consume multiple sugars, such as glucose and xylose, hinder industrial microbial processes for ethanol and lactate production. To overcome this limitation, I am engineering an E. coli co-culture system consisting of two ‘specialists'. One has the ability to only consume xylose and the other only glucose. This allows for co-utilization of lignocellulose-derived sugars so both sugars are completely consumed, residence time is reduced and lactate and ethanol titers are maximized.
ContributorsAyla, Zeynep Ece (Author) / Nielsen, David (Thesis director) / Flores, Andrew (Committee member) / Chemical Engineering Program (Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Escherichia coli is a bacterium that is used widely in metabolic engineering due to its ability to grow at a fast rate and to be cultured easily. E. coli can be engineered to produce many valuable chemicals, including biofuels and L-Phenylalanine—a precursor to many pharmaceuticals. Significant cell growth occurs in parallel to the biosynthesis of the desired biofuel or biochemical product, and limits product concentrations and yields. Stopping cell growth can improve chemical production since more resources will go toward chemical production than toward biomass. The goal of the project is to test different methods of controlling microbial uptake of nutrients, specifically phosphate, to dynamically limit cell growth and improve biochemical production of E. coli, and the research has the potential to promote public health, sustainability, and environment. This can be achieved by targeting phosphate transporter genes using CRISPRi and CRISPR, and they will limit the uptake of phosphate by targeting the phosphate transporter genes in DNA, which will stop transcriptions of the genes. In the experiment, NST74∆crr∆pykAF, a L-Phe overproducer, was used as the base strain, and the pitA phosphate transporter gene was targeted in the CRISPRi and CRISPR systems with the strain with other phosphate transporters knocked out. The tested CRISPRi and CRISPR mechanisms did not stop cell growth or improved L-Phe production. Further research will be conducted to determine the problem of the system. In addition, the CRISPRi and CRISPR systems that target multiple phosphate transporter genes will be tested in the future as well as the other method of stopping transcriptions of the phosphate transporter genes, which is called a tunable toggle switch mechanism.
ContributorsPark, Min Su (Author) / Nielsen, David (Thesis director) / Machas, Michael (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Membrane proteins are essential for cell survival and show potential as pharmacological and therapeutic targets in the field of nanobiotechnology.[1,2] In spite of their promise in these fields, research surrounding membrane proteins lags since their over-expression often leads to cell toxicity and death.[3,4] It was hypothesized that membrane protein expression could be regulated and optimized by modifying the heat shock response of Escherichia coli (E. coli). To test this hypothesis, the membrane protein expression pathway was reprogrammed using gene-blocks that were antisense to vital membrane protein DNA and RNA binding-site sequences and included an IbpA-σ32 heat shock promoter. Anti-PBAD and anti-HtdR gene-blocks were designed to have antisense sequences to the DNA of the arabinose PBAD promotor and Haloterrigena turkmenica deltarhodopsin (HtdR) transmembrane protein respectively. These sequences were then employed to be cloned into a pMM102 vector and grown in NEB-5α E. coli cells.
Stable glycerol stocks of the pIbpA-antiPBAD and pIbpA-antiHtdR in BW25113 cells with either a pBLN200 or pHtdR200 plasmid were created. Then after inducing the cells with L-arabinose and 10mM all-trans retinal to allow for membrane protein expression, spectrophotometry was used to test the optical density of the cells at an absorbance of 600nm. Although general trends showed that the pHtdR200-pMM102 and pHtdR200-pIbpA cells had lower optical densities than the pBLN200 cells of all types, the results were determined to be statistically insignificant. Continuing, the pHtdR200 cells of all types showed a purple phenotype when spun down, as expected, while the cells with the pBLN200 plasmid had a colorless phenotype in pellet form. Further work will include cloning a GFP gene-block to test the ability of the anti-PBAD sequence in tuning the transcription of the GFP protein.
Stable glycerol stocks of the pIbpA-antiPBAD and pIbpA-antiHtdR in BW25113 cells with either a pBLN200 or pHtdR200 plasmid were created. Then after inducing the cells with L-arabinose and 10mM all-trans retinal to allow for membrane protein expression, spectrophotometry was used to test the optical density of the cells at an absorbance of 600nm. Although general trends showed that the pHtdR200-pMM102 and pHtdR200-pIbpA cells had lower optical densities than the pBLN200 cells of all types, the results were determined to be statistically insignificant. Continuing, the pHtdR200 cells of all types showed a purple phenotype when spun down, as expected, while the cells with the pBLN200 plasmid had a colorless phenotype in pellet form. Further work will include cloning a GFP gene-block to test the ability of the anti-PBAD sequence in tuning the transcription of the GFP protein.
ContributorsBoese, Julia Nicole (Author) / Nannenga, Brent (Thesis director) / Holloway, Julianne (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Bad Samaritans are bystanders who omit from preventing some foreseeable harm when doing so could have been accomplished with little risk. Although failing to intervene to prevent a harm often renders Bad Samaritans morally culpable, under current common law in the United States they could not be held criminally liable for any harm that resulted to the victims of that harm. In this paper I argue for the criminalization of individuals who fall under this label; I argue for the adoption of Bad Samaritan laws. To accomplish this, I first argue for the conclusion that omissions can causally contribute to harm. From here I am able to reach three further conclusions relative to Bad Samaritan legislation. These three conclusions are that Bad Samaritan laws are justified, that the punishment for the violation of a Bad Samaritan law should be proportional to the degree culpability for the harm caused, and that if "commission by omission" statutes are justified, then so too are Bad Samaritan laws.
ContributorsCallahan, Ty William (Author) / Sigler, Mary (Thesis director) / Murphy, Jeffrie (Committee member) / Botham, Thad (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor) / Sandra Day O'Connor College of Law (Contributor) / School of Historical, Philosophical and Religious Studies (Contributor)
Created2013-05
Description
Protection orders are a common remedy for victims of domestic violence in Arizona, but problems of access and unnecessary complexity can prevent these orders from achieving their full potential impact. Through interviews with court officials and advocates, data collected from survivors of domestic violence and observation of court proceedings, this study takes a comprehensive look at how to make protection orders as effective and accessible as possible. This analysis concludes with a series of recommendations to improve the protection order process and guidelines for the information to be included in a comprehensive resource to help plaintiffs through the process.
ContributorsDavis, Lauren Elise (Author) / Durfee, Alesha (Thesis director) / Messing, Jill (Committee member) / Buel, Sarah (Committee member) / Barrett, The Honors College (Contributor) / School of Social Transformation (Contributor) / Sandra Day O'Connor College of Law (Contributor) / School of Historical, Philosophical and Religious Studies (Contributor)
Created2013-05