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- Creators: Barrett, The Honors College
- Creators: Nielsen, David
- Creators: Chabra, Rohin
- Status: Published
Description
Lignocellulosic biomass represents a renewable domestic feedstock that can support large-scale biochemical production processes for fuels and specialty chemicals. However, cost-effective conversion of lignocellulosic sugars into valuable chemicals by microorganisms still remains a challenge. Biomass recalcitrance to saccharification, microbial substrate utilization, bioproduct titer toxicity, and toxic chemicals associated with chemical pretreatments are at the center of the bottlenecks limiting further commercialization of lignocellulose conversion. Genetic and metabolic engineering has allowed researchers to manipulate microorganisms to overcome some of these challenges, but new innovative approaches are needed to make the process more commercially viable. Transport proteins represent an underexplored target in genetic engineering that can potentially help to control the input of lignocellulosic substrate and output of products/toxins in microbial biocatalysts. In this work, I characterize and explore the use of transport systems to increase substrate utilization, conserve energy, increase tolerance, and enhance biocatalyst performance.
ContributorsKurgan, Gavin (Author) / Wang, Xuan (Thesis advisor) / Nielsen, David (Committee member) / Misra, Rajeev (Committee member) / Nannenga, Brent (Committee member) / Arizona State University (Publisher)
Created2018
Description
In our modern world the source of for many chemicals is to acquire and refine oil. This process is becoming an expensive to the environment and to human health. Alternative processes for acquiring the final product have been developed but still need work. One product that is valuable is butanol. The normal process for butanol production is very intensive but there is a method to produce butanol from bacteria. This process is better because it is more environmentally safe than using oil. One problem however is that when the bacteria produce too much butanol it reaches the toxicity limit and stops the production of butanol. In order to keep butanol from reaching the toxicity limit an adsorbent is used to remove the butanol without harming the bacteria. The adsorbent is a mesoporous carbon powder that allows the butanol to be adsorbed on it. This thesis explores different designs for a magnetic separation process to extract the carbon powder from the culture.
ContributorsChabra, Rohin (Author) / Nielsen, David (Thesis director) / Torres, Cesar (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (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
Fermentation and humanity have a very long intertwined history, neither would exist without the other. Fermenting food preserves it so it can survive long beyond its normal shelf life by maintaining an environment that promotes the survival of healthy bacteria and not dangerous ones. Recently, largely thanks to the dawn of social media and the internet, the notion that eating healthily is important has once again come around. Kombucha has taken advantage of this revolution by promoting good tasting probiotics that are easily consumed and incorporated into day to day life. Sauerkraut and other fermented vegetables have not caught on because they are not presented in an easy to use format, there is no variety of flavoring, and consumers have no idea how to start eating it in their daily diet. This is the whole in the market that Fermentation Station is filling.
Normally, sauerkraut is only sold in very large containers that are intimidating to the average consumer. Fermentation Station will solve this issue by selling sauerkraut in small serving size containers or slightly bigger containers for a week long supply. Additionally, Fermentation Station will sell multiple different flavors of sauerkraut. This is necessary to intrigue a younger audience who desires variety and choice
The other place where sauerkraut falls short is that people are unaware of how to incorporate into their day to day meals. To solve this the company social media team has been growing its following on several platforms. By providing easy recipes through these platforms, consumers can see how they too can easily start eating more sauerkraut without actually altering their diet much. To augment the creator, Ryan Conley’s talents, two additional team members were brought on to help with branding and marketing, mostly on social media.
Normally, sauerkraut is only sold in very large containers that are intimidating to the average consumer. Fermentation Station will solve this issue by selling sauerkraut in small serving size containers or slightly bigger containers for a week long supply. Additionally, Fermentation Station will sell multiple different flavors of sauerkraut. This is necessary to intrigue a younger audience who desires variety and choice
The other place where sauerkraut falls short is that people are unaware of how to incorporate into their day to day meals. To solve this the company social media team has been growing its following on several platforms. By providing easy recipes through these platforms, consumers can see how they too can easily start eating more sauerkraut without actually altering their diet much. To augment the creator, Ryan Conley’s talents, two additional team members were brought on to help with branding and marketing, mostly on social media.
ContributorsConley, Ryan Christopher (Author) / Sebold, Brent (Thesis director) / Schoepf, Jared (Committee member) / School of International Letters and Cultures (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
Northern peatland carbon cycling is under close observation and is critical to include in models projecting the future effects of climate change as these ecosystems represent a significant source of atmospheric methane (CH4). Changes in the in situ conditions, brought upon by the warming climate, could alter the rates of organic matter decomposition and accelerate the emissions of greenhouse, changing northern peatland’s status as a carbon sink. In order to develop a better understanding of the climate’s effect on the microbial community composition, carbon decomposition cascade, and flux of CH4 and CO2, anoxic soil microcosms were supplemented with either glucose or propionate to test the distinct intermediary metabolism of four northern peatland sites with statistically similar geochemistry that exist across a climate gradient. Lutose (LT) and Bog Lake (BL) consumed the supplemented glucose at the highest rates, 42.6 mg/L per day and 39.5 mg/L per day respectively. Chicago Bog (CB) and Daring Lake (DL) consumed the supplemented propionate at the highest rates, 5.26 mg/L per day and 4.34 mg/L per day respectively. BL microcosms showed low levels of methanogenesis as CH4 concentrations reached a maximum of 2.61 µmol/g dry soil in the treatments. In DL, the site with the highest production of CH4, the low abundance of hydrogenotrophic methanogens (Methanocellaceae and Methanoregulaceae) and relatively steady concentrations of acetate and formate could indicate that these are the more desired methanogenic substrates. These findings are indicative of the differences in metabolic potential found across these geochemically similar peatlands, lending to climate variables being a major driver in microbial community potential. To further characterize the intermediary metabolism and the effect of the climate gradient in these sites, future experimentations should incorporate 13C DNA-stable isotope probing data, establish a mass balance of the system, and incubate the microcosms at their respective in situ temperatures.
ContributorsBourquin, Brandon Phillip (Author) / Cadillo-Quiroz, Hinsby (Thesis director) / Marcus, Andrew (Committee member) / Sarno, Analissa F. (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
The microalgae Scenedesmus have been regarded as a potential source for biofuel production, having up to ~30% of dry weight as lipids used for biodiesel fuel production. Electro-selective fermentation (ESF) is a novel approach that can selectively degrade proteins and carbohydrates while conserving lipids within algal cells, while simultaneously enhancing lipid wet-extraction and biohydrogenation. ESF is a combination of SF and Microbial Electrolysis Cell (MEC) technologies. Experiments reported here prove that ESF is an effective means of enhancing lipid wet-extraction by ~50% and achieving 36% higher lipid saturation conversion, compared to SF, over 30 days of semi-continuous operation. Anode-respiring bacteria (ARB) residing on the anode surface produced a current that led to increased rate of organic substrate utilization, protein degradation, and ultimately enhanced lipid extraction and biohydrogenation that converted unsaturated to saturated fatty-acids. Thus, ESF provides a promising method for enhancing lipid extraction for biofuel production.
ContributorsRastogi, Neil K (Author) / Rittmann, Bruce (Thesis director) / Liu, Liu (Committee member) / Chemical Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
The purpose behind this research was to identify unknown transport proteins involved in lactate export. Lactate bioproduction is an environmentally beneficial alternative to petroleum-based plastic production as it produces less toxic waste byproduct and can rely on microbial degradation of otherwise wasted biomass. Coupled with appropriate product refinement, industrial microbial producers can be genetically engineered to generate quantities of bioplastic approaching 400 million metric tons each year. However, this process is not entirely suitable for large investment, as the fermentative bottlenecks, including product export and homeostasis control, limit production metrics. Previous studies have based their efforts on enhancing cellular machinery, but there remain uncharacterized membrane proteins involved in product export yet to be determined. It has been seen that deletion of known lactate transporters in Escherichia coli resulted in a decrease in lactate production, unlike the expected inhibition of export. This indicates that there exist membrane proteins with the ability to export lactate which may have another similar substrate it primarily transports.To identify these proteins, I constructed a genomic library of all genes in an engineered lactate producing E. coli strain, with known transporter genes deleted, and systematically screened for potential lactate transporter proteins. Plasmids and their isolated proteins were compared utilizing anaerobic plating to identify genes through sanger sequencing. With this method, I identified two proteins, yiaN and ybhL-ybhM, which did not show any significant improvement in lactate production when tested. Attempts were made to improve library diversity, resulting in isopropyl-β-D-1-thiogalactopyranoside induction as a likely factor for increased expression of potential fermentation-associated proteins. A genomic library from Lactobacillus plantarum was constructed and screened for transport proteins which could improve lactate production. Results showed that isolated plasmids contained no notable inserts, indicating that the initial transformation limited diversity. Lastly, I compared the results from genomic screening with overexpression of target transporter genes by computational substrate similarity search. Induced expression of ttdT, citT and dcuA together significantly increased lactate export and thus production metrics as well as cell growth. These positive results indicate an effective means of determining substrate promiscuity in membrane proteins with similar organic acid transport capacity.
ContributorsLee-Kin, Jared (Author) / Wang, Xuan (Thesis advisor) / Nielsen, David (Committee member) / Varman, Arul (Committee member) / Arizona State University (Publisher)
Created2022
Description
Heterotrophs such as E. coli contain metabolic pathways with enzymes called carboxylases that are capable of fixing CO2 gas to form metabolites, which has implications for aiding with CO2’s role in climate change. The reductive branch of the tricarboxylic acid (TCA) cycle serves as an important pathway for NAD+ regeneration in enteric bacteria in anaerobic conditions and leads to the production of succinate, a useful industrial product. The enzyme phosphoenolpyruvate carboxykinase is responsible for fixing CO2 in the conversion of PEP to OAA within this pathway and has potential to be a significant carbon fixation module in heterotrophic organisms. This project explored pck genes from select organisms by transforming plasmids to test if these variants have improved kinetics compared to the native E. coli Pck and to investigate their ability to improve succinate bioproduction.
ContributorsModukuri, Shree (Author) / Wang, Xuan (Thesis director) / Godar, Amanda (Committee member) / Barrett, The Honors College (Contributor) / School of Molecular Sciences (Contributor) / School of International Letters and Cultures (Contributor)
Created2024-05