Matching Items (18)
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- All Subjects: E. coli
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- 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 objective of this research is to create biodegradable mats with tunable characteristics such as fiber diameter and surface area. The drug delivery mats enable spatially controlled delivery of disease-specific therapeutics. Using a large electric potential to draw fibers from a solution flowing at a specific rate, the polymer fibers reach a grounded target several inches away. The biodegradable polymer used in this study was poly(lactic acid-co-glycolic acid) (PLGA). PLGA solutions ranging from 0.5 to 27 wt.% were prepared by dissolving the block copolymer in a solvent mixture containing tetrahydrofuran (THF) and dimethylformamide (DMF) at a 3:1 weight ratio. They were then electrospun at needle-to-target distances of 7, 14, and 18 cm and rates ranging from 0.8 to 4 mL/h. The range of voltage used was between 8 – 15 kV, which was based on the observation of the formation of a Taylor cone, largely affected by on the environment and weather (e.g., temperature and humidity in the lab). A 27 wt.% PLGA solution, electrospun at 1 mL/h at a voltage of 11.25 kV and needle-to-target distance of 14 cm produced uniform fibers with an average fiber diameter of 0.985 m. All other parameters outside the range given created beaded fibers. In addition, solution rheology was performed on some of the PLGA solution to measure viscosity, which is directly correlated to the fiber diameter of the electrospun mats. Observing the impact of solvent on fiber spinning and fiber diameter brings about many positive results in developing fully characterized and well-understood fibrous mats for drug delivery. The nanoscale fibers will be used as drug delivery mats and, therefore, the biodegradation kinetics of the polymers will be studied. Next, parameters of the polymers as well as the polymeric mats will be correlated to the degradation-mediated release of small molecule therapeutics (e.g., peptides, drugs, etc.) such that time-resolved dosing profiles can be created.
ContributorsLent, Madeline (Author) / Green, Matthew (Thesis director) / Holloway, Julianne (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
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
Hydrothermal Liquefaction of Algae represents one of many pathways for the sustainable replacement of fossil fuels in transportation. When processing and researching algal biofuel, determination of the higher heating value (HHV) is paramount. Bomb calorimetry represents to current method for direct determination of HHV. When determining HHV’s indirectly, the industry standard is using one of many linear correlations relating elemental composition to HHV. Most of these correlations were developed from coal industry data, meaning that they do not necessarily fit algal product data well. In this study bomb calorimetry data and CHNS/O elemental composition data were collected for Chlorella, Micract, GS 5587.1, Kirchnella, and Gal 87.1 MM8 algae species. This data was added to CHNS/O and HHV values for other algal products in literature, and utilized to test the accuracy of the Dulong, Gumz, Vandralek and Boie correlations for algae products. Several preliminary algae specific correlations were proposed through a linear regression model of the data. Of the 5 samples tested, Kirchnella exhibited the highest HHV (23.2405 ± 0.0216 MJ/kg) and Chlorella exhibited the lowest (20.2055 ± 0.0484 MJ/kg). For both the experimental, and literature CHNS/O vs HHV data, the Vandralek and Boie correlations provided the best approximations in this study. For the totality of the data collected and researched in this study, 6 of 8 proposed correlations outperformed the Vandralek equation for HHV approximation. The most promising proposed correlations incorporated multiple linear regressions for elemental fractions of CHS, CHSO and CHNSO. Being that only 20 distinct algal product samples were regressed to create the proposed correlations, more data should be incorporated before publication of a final correlation. This study should serve as a starting point for the compilation of an exhaustive database for algal product assay and HHV data.
ContributorsCopp, Connor Joseph (Author) / Deng, Shuguang (Thesis director) / Muppaneni, Tapaswy (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
A growing number of stylists \u2014 cosmetologists \u2014 are finding it harder to afford the basic necessities such as rent. However, the ever-increasing presence of smartphones and the increasing need for on-demand services like Uber and Uber Eats creates a unique opportunity for stylists \u2014 Clippr. Clippr is an application that aims to connect individual stylists directly to their customers. The application gives stylists a platform to create and display their own prices, services, and portfolio. Customers get the benefit of finding a stylist that suits them and booking instantly. This project outlines the backend for the Clippr application. It goes over the framework, REST API, and various functionalities of the application. Additionally, the project also covers the work that is still needed to successfully launch the application.
ContributorsKamath, Sanketh (Author) / Olsen, Christopher (Thesis director) / Sebold, Brent (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Obtaining access to clean water is a global problem that is becoming more important with increasing population and advancing technology. Desalination through reverse osmosis (RO) is a promising technology takes advantage of the global supply of saline water to augment its limited freshwater reservoirs. To increase RO membrane performance, the feedwater is pretreated to take any excess pollutants out before the desalination. These pretreatment membranes are susceptible to fouling, which reduces efficiency and drives up costs of the overall process. Increasing the hydrophilicity of these membranes would reduce fouling, and electrospinning is a production method of pretreatment membranes with the capability to control hydrophilicity. This work explores how the composition of electrospun fibrous membranes containing blends of hydrophilic and hydrophobic polymers affects membrane characteristics such as wettability as well as filtration performance. Nonwoven, nanoscale membranes were prepared using electrospinning with a targeted application of pretreatment in water filtration. Using a rotating collector, electrospun mats of hydrophobic poly(vinyl chloride) (PVC) and hydrophilic poly(vinyl alcohol) (PVA) were simultaneously deposited from separate polymer solutions, and their polymer compositions were then characterized using Fourier Transform Infrared (FTIR) spectra. The data did not reveal a reliable correlation established between experimental control variables like flow rate and membrane composition. However, when the membranes' hydrophilicity was analyzed using static water contact angle measurements, a trend between PVA content and hydrophilicity was seen. This shows that the hypothesis of increasing PVA content to increase hydrophilicity is reliable, but with the current experimental design the PVA content is not controllable. Therefore, the primary future work is making a new experimental setup that will be able to better control membrane composition. Filtration studies to test for fouling and size exclusion will be performed once this control is obtained.
ContributorsTronstad, Zachary (Author) / Green, Matthew (Thesis director) / Holloway, Julianne (Committee member) / Epps, Thomas (Committee member) / Chemical Engineering Program (Contributor) / Materials Science and Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-12
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
The following thesis documents a two-fold approach to investigate challenges pertaining to water purification, first through a meta-analysis of ionic liquid toxicity, then through experimentation aimed at developing water pre-treatment membranes. Ionic liquids (ILs) are salts with low melting points, typically liquid at room temperature. Several extraordinary physical attributes, e.g. low viscosity, high conductivity, low to no vapor pressure, etc., and seemingly unlimited combinations available, have pushed IL research to the forefront of many research fronts. Concerns are raised as ionic liquids are rushed into commercial production without sufficient environmental regulation. Research has shown that the chemicals are in fact toxic, yet have developed a reputation for being “green” chemicals due to select physical attributes and applications. The meta-analysis discussed focuses on industry perception of ionic liquid toxicity through a patent review, and considers toxicity of ILs comparatively against other chemical families with well-established toxicity. The meta-analysis revealed that the total patent literature pertaining to ILs (n=3358) resulted in 112 patents that addressed the toxicity of ILs, and notably few (n=17) patents defined ILs as toxic, representing only 0.51% of the evaluated body of work on intellectual property claims. Additionally, toxicity of ionic liquids is comparable to that of other chemical families.
The objective of the experimentation was to explore the effect of crosslinker chain length on the morphology of nanofiber mats. Specifically, poly(vinyl alcohol (PVA) was electrospun into nanofiber mats and poly(ethylene) glycol bis(carboxylic acid) (PEG diacid) was used as the crosslinking agent. As-spun fibers had average fiber diameter of 70 ± 30 nm with an average pore size of 0.10 ± 0.16 μm^2. The fiber diameter for the mats crosslinked with the shorter PEG diacid (Mn = 250) increased to 110 ± 40 nm with an average pore size of 0.11 ± 0.04 μm^2. The mats crosslinked with the longer PEG diacid (Mn = 600) had fiber diameters of 180 ± 10 nm with an average pore size 0.01 ± 0.02 μm^2.
The objective of the experimentation was to explore the effect of crosslinker chain length on the morphology of nanofiber mats. Specifically, poly(vinyl alcohol (PVA) was electrospun into nanofiber mats and poly(ethylene) glycol bis(carboxylic acid) (PEG diacid) was used as the crosslinking agent. As-spun fibers had average fiber diameter of 70 ± 30 nm with an average pore size of 0.10 ± 0.16 μm^2. The fiber diameter for the mats crosslinked with the shorter PEG diacid (Mn = 250) increased to 110 ± 40 nm with an average pore size of 0.11 ± 0.04 μm^2. The mats crosslinked with the longer PEG diacid (Mn = 600) had fiber diameters of 180 ± 10 nm with an average pore size 0.01 ± 0.02 μm^2.
ContributorsRomero, Felicia Navidad (Author) / Green, Matthew D. (Thesis director) / Lind, Mary Laura (Committee member) / Long, Timothy E. (Committee member) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05