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- All Subjects: Escherichia coli
- Creators: Nielsen, David
- Status: Published
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
Synthetic biology and metabolic engineering has aided the production of chemicals using renewable resources, thus offering a solution to our dependence on the dwindling petroleum resources. While a major portion of petroleum resources go towards production of fuels, a significant fraction also goes towards production of specialty chemicals. There has been a growing interest in recent years in commercializing bio-based production of such high value compounds. In this thesis the biosynthesis of aromatic esters has been explored, which have typical application as flavor and fragrance additive to food, drinks and cosmetics. Recent progress in pathway engineering has led to the construction of several aromatic alcohol producing pathways, the likes of which can be utilized to engineer aromatic ester biosynthesis by addition of a suitable enzyme from the acyltransferase class. Enzyme selection and screening done in this work has identified chloramphenicol O-acetyltransferase enzyme(CAT) as a potential candidate to complete the biosynthetic pathways for each of 2-phenethyl acetate, benzyl acetate, phenyl acetate and acetyl salicylate. In the end, E. coli strains capable of producing up to 60 mg/L 2-phenethyl acetate directly from glucose were successfully constructed by co-expressing CAT in a previously engineered 2-phenylethanol producing host.
ContributorsMadathil Soman Pillai, Karthika (Author) / Nielsen, David (Thesis advisor) / Wang, Xuan (Committee member) / Torres, Cesar (Committee member) / Arizona State University (Publisher)
Created2016
Description
Fossil fuels have been the primary source of energy in the world for many decades. However, they are among the top contributors of the greenhouse gas emissions in the atmosphere. The objective of this research was to produce a more environmentally friendly biofuel from Algae-Helix and Salicornia biomasses. Experiments were conducted using a hydrothermal liquefaction (HTL) technique in the HTL reactor to produce biofuel that can potentially replace fossil fuel usage. Hydrothermal Liquefaction is a method used to convert the biomass into the biofuels. HTL experiments on Algae-Helix and Salicornia at 200°C-350°C and 430psi were performed to investigate the effect of temperature on the biocrude yield of the respective biomass used. The effect of the biomass mixture (co-liquefaction) of Salicornia and algae on the amount of biocrude produced was also explored. The biocrude and biochar (by-product) obtained from the hydrothermal liquefaction process were also analyzed using thermogravimetric analyzer (TGA). The maximum biocrude yield for the algae-helix biomass and for the Salicornia biomass were both obtained at 300°C which were 34.63% and 7.65% respectively. The co-liquefaction of the two biomasses by 50:50 provided a maximum yield of 17.26% at 250°C. The co-liquefaction of different ratios explored at 250°C and 300°C concluded that Salicornia to algae-helix ratio of 20:80 produced the highest yields of 22.70% and 31.97%. These results showed that co-liquefaction of biomass if paired well with the optimizing temperature can produce a high biocrude yield. The TGA profiles investigated have shown that salicornia has higher levels of ash content in comparison with the algae-helix. It was then recommended that for a mixture of algae and Salicornia, large-scale biofuel production should be conducted at 250℃ in a 20:80 salicornia to algae biocrude ratio, since it lowers energy needs. The high biochar content left can be recycled to optimize biomass, and prevent wastage.
ContributorsLaideson, Maymary Everrest (Co-author) / Luboowa, Kato (Co-author) / Deng, Shuguang (Thesis director) / Nielsen, David (Committee member) / Chemical Engineering Program (Contributor) / Economics Program in CLAS (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Fossil fuels have been the primary source of energy in the world for many decades. However, they are among the top contributors of the greenhouse gas emissions in the atmosphere. The objective of this research was to produce a more environmentally friendly biofuel from Algae-Helix and Salicornia biomasses. Experiments were conducted using a hydrothermal liquefaction (HTL) technique in the HTL reactor to produce biofuel that can potentially replace fossil fuel usage. Hydrothermal Liquefaction is a method used to convert the biomass into the biofuels. HTL experiments on Algae-Helix and Salicornia at 200°C-350°C and 430psi were performed to investigate the effect of temperature on the biocrude yield of the respective biomass used. The effect of the biomass mixture (co-liquefaction) of Salicornia and algae on the amount of biocrude produced was also explored. The biocrude and biochar (by-product) obtained from the hydrothermal liquefaction process were also analyzed using thermogravimetric analyzer (TGA). The maximum biocrude yield for the algae-helix biomass and for the Salicornia biomass were both obtained at 300°C which were 34.63% and 7.65% respectively. The co-liquefaction of the two biomasses by 50:50 provided a maximum yield of 17.26% at 250°C. The co-liquefaction of different ratios explored at 250°C and 300°C concluded that Salicornia to algae-helix ratio of 20:80 produced the highest yields of 22.70% and 31.97%. These results showed that co-liquefaction of biomass if paired well with the optimizing temperature can produce a high biocrude yield. The TGA profiles investigated have shown that salicornia has higher levels of ash content in comparison with the algae-helix. It was then recommended that for a mixture of algae and Salicornia, large-scale biofuel production should be conducted at 250℃ in a 20:80 salicornia to algae biocrude ratio, since it lowers energy needs. The high biochar content left can be recycled to optimize biomass, and prevent wastage.
ContributorsLuboowa, Kato Muhammed (Co-author) / Laideson, Maymary (Co-author) / Deng, Shuguang (Thesis director) / Nielsen, David (Committee member) / Chemical Engineering Program (Contributor) / School of Sustainability (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