Matching Items (134)
Description
The advantages and challenges of combining zero-valent iron (ZVI) and microbial reduction of trichloroethene (TCE) and perchlorate (ClO4-) in contaminated soil and groundwater are not well understood. The objective of this work was to identify the benefits and limitations of simultaneous application of ZVI and bioaugmentation for detoxification of TCE and ClO4- using conditions relevant to a specific contaminated site. We studied conditions representing a ZVI-injection zone and a downstream zone influenced Fe (II) produced, for simultaneous ZVI and microbial reductive dechlorination applications using bench scale semi-batch microcosm experiments. 16.5 g L-1 ZVI effectively reduced TCE to ethene and ethane but ClO4- was barely reduced. Microbial reductive dechlorination was limited by both ZVI as well as Fe (II) derived from oxidation of ZVI. In the case of TCE, rapid abiotic TCE reduction made the TCE unavailable for the dechlorinating bacteria. In the case of perchlorate, ZVI inhibited the indigenous perchlorate-reducing bacteria present in the soil and groundwater. Further, H2 generated by ZVI reactions stimulated competing microbial processes like sulfate reduction and methanogenesis. In the microcosms representing the ZVI downstream zone (Fe (II) only), we detected accumulation of cis-dichloroethene (cis-DCE) and vinyl chloride (VC) after 56 days. Some ethene also formed under these conditions. In the absence of ZVI or Fe (II), we detected complete TCE dechlorination to ethene and faster rates of ClO4- reduction. The results illustrate potential limitations of combining ZVI with microbial reduction of chlorinated compounds and show the potential that each technology has when applied separately.
ContributorsMohana Rangan, Srivatsan (Author) / Krajmalnik-Brown, Rosa (Thesis advisor) / Delgado, Anca G (Committee member) / Lowry, Gregory V. (Committee member) / Arizona State University (Publisher)
Created2017
Description
ABSTRACT
Sustainable global energy production is one of the grand challenges of the 21st century. Next-generation renewable energy sources include using photosynthetic microbes such as cyanobacteria for efficient production of sustainable fuels from sunlight. The cyanobacterium Synechocystis PCC 6803 (Synechocystis) is a genetically tractable model organism for plant-like photosynthesis that is used to develop microbial biofuel technologies. However, outside of photosynthetic processes, relatively little is known about the biology of microbial phototrophs such as Synechocystis, which impairs their development into market-ready technologies. My research objective was to characterize strategic aspects of Synechocystis biology related to its use in biofuel production; specifically, how the cell surface modulates the interactions between Synechocystis cells and the environment. First, I documented extensive biofouling, or unwanted biofilm formation, in a 4,000-liter roof-top photobioreactor (PBR) used to cultivate Synechocystis, and correlated this cell-binding phenotype with changes in nutrient status by developing a bench-scale assay for axenic phototrophic biofilm formation. Second, I created a library of mutants that lack cell surface structures, and used this biofilm assay to show that mutants lacking the structures pili or S-layer have a non-biofouling phenotype. Third, I analyzed the transcriptomes of cultures showing aggregation, another cell-binding phenotype, and demonstrated that the cells were undergoing stringent response, a type of conserved stress response. Finally, I used contaminant Consortia and statistical modeling to test whether Synechocystis mutants lacking cell surface structures could reduce contaminant growth in mixed cultures. In summary, I have identified genetic and environmental means of manipulating Synechocystis strains for customized adhesion phenotypes, for more economical biomass harvesting and non-biofouling methods. Additionally, I developed a modified biofilm assay and demonstrated its utility in closing a key gap in the field of microbiology related to axenic phototrophic biofilm formation assays. Also, I demonstrated that statistical modeling of contaminant Consortia predicts contaminant growth across diverse species. Collectively, these findings serve as the basis for immediately lowering the cost barrier of Synechocystis biofuels via a more economical biomass-dewatering step, and provide new research tools for improving Synechocystis strains and culture ecology management for improved biofuel production.
Sustainable global energy production is one of the grand challenges of the 21st century. Next-generation renewable energy sources include using photosynthetic microbes such as cyanobacteria for efficient production of sustainable fuels from sunlight. The cyanobacterium Synechocystis PCC 6803 (Synechocystis) is a genetically tractable model organism for plant-like photosynthesis that is used to develop microbial biofuel technologies. However, outside of photosynthetic processes, relatively little is known about the biology of microbial phototrophs such as Synechocystis, which impairs their development into market-ready technologies. My research objective was to characterize strategic aspects of Synechocystis biology related to its use in biofuel production; specifically, how the cell surface modulates the interactions between Synechocystis cells and the environment. First, I documented extensive biofouling, or unwanted biofilm formation, in a 4,000-liter roof-top photobioreactor (PBR) used to cultivate Synechocystis, and correlated this cell-binding phenotype with changes in nutrient status by developing a bench-scale assay for axenic phototrophic biofilm formation. Second, I created a library of mutants that lack cell surface structures, and used this biofilm assay to show that mutants lacking the structures pili or S-layer have a non-biofouling phenotype. Third, I analyzed the transcriptomes of cultures showing aggregation, another cell-binding phenotype, and demonstrated that the cells were undergoing stringent response, a type of conserved stress response. Finally, I used contaminant Consortia and statistical modeling to test whether Synechocystis mutants lacking cell surface structures could reduce contaminant growth in mixed cultures. In summary, I have identified genetic and environmental means of manipulating Synechocystis strains for customized adhesion phenotypes, for more economical biomass harvesting and non-biofouling methods. Additionally, I developed a modified biofilm assay and demonstrated its utility in closing a key gap in the field of microbiology related to axenic phototrophic biofilm formation assays. Also, I demonstrated that statistical modeling of contaminant Consortia predicts contaminant growth across diverse species. Collectively, these findings serve as the basis for immediately lowering the cost barrier of Synechocystis biofuels via a more economical biomass-dewatering step, and provide new research tools for improving Synechocystis strains and culture ecology management for improved biofuel production.
ContributorsAllen, Rebecca Custer (Author) / Curtiss Iii, Roy (Thesis advisor) / Krajmalnik-Brown, Rosa (Thesis advisor) / Rittmann, Bruce E. (Committee member) / Vermaas, Willem (Committee member) / Arizona State University (Publisher)
Created2016
Description
Biological soil crusts (BSCs), topsoil microbial assemblages typical of arid land ecosystems, provide essential ecosystem services such as soil fertilization and stabilization against erosion. Cyanobacteria and lichens, sometimes mosses, drive BSC as primary producers, but metabolic activity is restricted to periods of hydration associated with precipitation. Climate models for the SW United States predict changes in precipitation frequency as a major outcome of global warming, even if models differ on the sign and magnitude of the change. BSC organisms are clearly well adapted to withstand desiccation and prolonged drought, but it is unknown if and how an alteration of the precipitation frequency may impact community composition, diversity, and ecosystem functions. To test this, we set up a BSC microcosm experiment with variable precipitation frequency treatments using a local, cyanobacteria-dominated, early-succession BSC maintained under controlled conditions in a greenhouse. Precipitation pulse size was kept constant but 11 different drought intervals were imposed, ranging between 416 to 3 days, during a period of 416 days. At the end of the experiments, bacterial community composition was analyzed by pyrosequencing of the 16s rRNA genes in the community, and a battery of functional assays were used to evaluate carbon and nitrogen cycling potentials. While changes in community composition were neither marked nor consistent at the Phylum level, there was a significant trend of decreased diversity with increasing precipitation frequency, and we detected particular bacterial phylotypes that responded to the frequency of precipitation in a consistent manner (either positively or negatively). A significant trend of increased respiration with increasingly long drought period was detected, but BSC could recover quickly from this effect. Gross photosynthesis, nitrification and denitrification remained essentially impervious to treatment. These results are consistent with the notion that BSC community structure adjustments sufficed to provide significant functional resilience, and allow us to predict that future alterations in precipitation frequency are unlikely to result in severe impacts to BSC biology or ecological relevance.
ContributorsMyers, Natalie Kristine (Author) / Garcia-Pichel, Ferran (Thesis advisor) / Hall, Sharon (Committee member) / Turner, Benjamin (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Arizona State University (Publisher)
Created2013
Description
Phytoplankton comprise the base of the marine food web, and, along with heterotrophic protists, they are key players in the biological pump that transports carbon from the surface to the deep ocean. In the world's subtropical oligotrophic gyres, plankton communities exhibit strong seasonality. Winter storms vent deep water into the euphotic zone, triggering a surge in primary productivity in the form of a spring phytoplankton bloom. Although the hydrographic trends of this "boom and bust" cycle have been well studied for decades, community composition and its seasonal and annual variability remains an integral subject of research. It is hypothesized here that proportions of different phytoplankton and protistan taxa vary dramatically between seasons and years, and that picoplankton represent an important component of this community and contributor to carbon in the surface ocean. Monthly samples from the Bermuda Atlantic Time-series Study (BATS) site were analyzed by epifluorescence microscopy, which permits classification by morphology, size, and trophic type. Epifluorescence counts were supplemented with flow cytometric quantification of Synechococcus, Prochlorococcus, and autotrophic pico- and nanoeukaryotes. Results from this study indicate Synechococcus and Prochlorococcus, prymnesiophytes, and hetero- and mixotrophic nano- and dinoflagellates were the major players in the BATS region plankton community. Ciliates, cryptophytes, diatoms, unidentified phototrophs, and other taxa represented rarer groups. Both flow cytometry and epifluorescence microscopy revealed Synechococcus to be most prevalent during the spring bloom. Prymnesiophytes likewise displayed distinct seasonality, with the highest concentrations again being noted during the bloom. Heterotrophic nano- and dinoflagellates, however, were most common in fall and winter. Mixotrophic dinoflagellates, while less abundant than their heterotrophic counterparts, displayed similar seasonality. A key finding of this study was the interannual variability revealed between the two years. While most taxa were more abundant in the first year, prymnesiophytes experienced much greater abundance in the second year bloom. Analyses of integrated carbon revealed further stark contrasts between the two years, both in terms of total carbon and the contributions of different groups. Total integrated carbon varied widely in the first study year but displayed less fluctuation after June 2009, and values were noticeably reduced in the second year.
ContributorsHansen, Amy (Author) / Neuer, Susanne (Thesis advisor) / Krajmalnik-Brown, Rosa (Committee member) / Sommerfeld, Milton (Committee member) / Arizona State University (Publisher)
Created2010
Description
The objective of this research was to predict the persistence of potential future contaminants in indirect potable reuse systems. In order to accurately estimate the fates of future contaminants in indirect potable reuse systems, results describing persistence from EPI Suite were modified to include sorption and oxidation. The target future contaminants studied were the approximately 2000 pharmaceuticals currently undergoing testing by United States Food and Drug Administration (US FDA). Specific organic substances such as analgesics, antibiotics, and pesticides were used to verify the predicted half-lives by comparing with reported values in the literature. During sub-surface transport, an important component of indirect potable reuse systems, the effects of sorption and oxidation are important mechanisms. These mechanisms are not considered by the quantitative structure activity relationship (QSAR) model predictions for half-lives from EPI Suite. Modifying the predictions from EPI Suite to include the effects of sorption and oxidation greatly improved the accuracy of predictions in the sub-surface environment. During validation, the error was reduced by over 50% when the predictions were modified to include sorption and oxidation. Molecular weight (MW) is an important criteria for estimating the persistence of chemicals in the sub-surface environment. EPI Suite predicts that high MW compounds are persistent since the QSAR model assumes steric hindrances will prevent transformations. Therefore, results from EPI Suite can be very misleading for high MW compounds. Persistence was affected by the total number of halogen atoms in chemicals more than the sum of N-heterocyclic aromatics in chemicals. Most contaminants (over 90%) were non-persistent in the sub-surface environment suggesting that the target future drugs do not pose a significant risk to potable reuse systems. Another important finding is that the percentage of compounds produced from the biotechnology industry is increasing rapidly and should dominate the future production of pharmaceuticals. In turn, pharmaceuticals should become less persistent in the future. An evaluation of indirect potable reuse systems that use reverse osmosis (RO) for potential rejection of the target contaminants was performed by statistical analysis. Most target compounds (over 95%) can be removed by RO based on size rejection and other removal mechanisms.
ContributorsLim, Seung (Author) / Fox, Peter (Thesis advisor) / Abbaszadegan, Morteza (Committee member) / Halden, Rolf (Committee member) / Arizona State University (Publisher)
Created2011
Description
Trichloroethene (TCE) and hexavalent chromium [Cr(VI)] are toxic and carcinogenic contaminants found in drinking water resources across the United States. A series of Bench-scale treatability studies were conducted to evaluate the effectiveness of a consortium of facultative and strictly anaerobic bacteria, KB-1®, to remove TCE and Cr(VI) from a contaminated aquifer in San Diego. These series of treatability studies were also performed to prepare data and mature packed sediment columns for the deployment of the In Situ Microcosm Array (ISMA), a diagnostic device for determining optimal treatments for a contaminated aquifer, at this particular site. First, a control panel for the ISMA’s Injection Module (IM) was created in order to deliver nutrients to the columns. Then, a column treatability study was performed in order to produce columns with an established KB-1® consortium, so that all TCE in the column influent was converted to ethene by the time it had exited the column. Finally, a batch bottle treatability study was performed to determine KB-1®’s effectiveness at remediating both TCE and Cr(VI) from the San Diego ground-water samples. The results from the column study found that KB-1® was able to reduce TCE in mineral media. However, in the presence of site ground-water for the batch bottle study, KB-1® was only able to reduce Cr(VI) and no TCE dechlorination was observed. This result suggests that the dechlorinating culture cannot survive prolonged exposure to Cr(VI). Therefore, future work may involve repeating the batch bottle study with Cr(VI) removed from the groundwater prior to inoculation to determine if KB-1® is then able to dechlorinate TCE.
ContributorsDuong, Benjamin Taylor (Author) / Halden, Rolf (Thesis director) / Torres, Cesar (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Barrett, The Honors College (Contributor) / School of Dance (Contributor) / Chemical Engineering Program (Contributor)
Created2013-05
Description
Plastics continue to benefit society in innumerable ways, even though recent public focus on plastics has centered mostly on human health and environmental concerns, including their endocrine-disrupting properties and the long-term pollution they represent. The benefits of plastics are particularly apparent in medicine and public health. Plastics are versatile, cost-effective, require less energy to produce than alternative materials like metal or glass, and can be manufactured to have many different properties. Due to these characteristics, polymers are used in diverse health applications like disposable syringes and intravenous bags, sterile packaging for medical instruments as well as in joint replacements, tissue engineering, etc. However, not all current uses of plastics are prudent and sustainable, as illustrated by the widespread, unwanted human exposure to endocrine-disrupting bisphenol A (BPA) and di-(2-ethylhexyl) phthalate (DEHP), problems arising from the large quantities of plastic being disposed of, and depletion of non-renewable petroleum resources as a result of the ever-increasing mass production of plastic consumer articles. Using the health-care sector as example, this review concentrates on the benefits and downsides of plastics and identifies opportunities to change the composition and disposal practices of these invaluable polymers for a more sustainable future consumption. It highlights ongoing efforts to phase out DEHP and BPA in the health-care and food industry and discusses biodegradable options for plastic packaging, opportunities for reducing plastic medical waste, and recycling in medical facilities in the quest to reap a maximum of benefits from polymers without compromising human health or the environment in the process.
ContributorsNorth, Emily Jean (Co-author) / Halden, Rolf (Co-author, Thesis director) / Mikhail, Chester (Committee member) / Hurlbut, Ben (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Statistical Sciences (Contributor) / Chemical Engineering Program (Contributor)
Created2013-05
Description
The effect of ammonium on microbial fermentation was investigated to improve the efficiency of microbial electrochemical cells (MXC). Electron balances of anaerobic microbial cultures with varying ammonium concentrations (reported as g N-NH4+/L) were used to study the distribution of electrons from different fermentable substrates to acetate, propionate, and methane. Results showed that with a high ammonium concentration (between 2.25 to 3g N-NH4+/L) fewer electrons routed to methane during the fermentation of 300 me-eq./L of electron donors .The majority of electrons (~ 60-80%) in the serum bottles experiments were routed to acetate and propionate for all fermentable substrates with high ammonium concentration. While methane cannot be utilized by anode respiring bacteria (ARBs) to produce current, both acetate and propionate can, which could lead to higher Coulombic efficiencies in MXCs. Experiments in microbial electrolysis cells (MECs) with glucose, lactate, and ethanol were performed. MEC experiments showed low percentage of electrons to current (between 10-30 %), potentially due to low anode surface area (~ 3cm2) used during these experiments. Nevertheless, the fermentation process observed in the MECs was similar to serum bottles results which showed significant diversion of electrons to acetate and propionate (~ 80%) for a control concentration of 0.5 g N-NH4+/L .
ContributorsLozada Guerra, Suyana Patricia (Co-author) / Joseph, Miceli (Co-author) / Krajmalnik-Brown, Rosa (Thesis director) / Torres, Cesar (Committee member) / Young, Michelle (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2013-05
Description
Influenza remains a constant concern for public health agencies across the nation and worldwide. Current methods of surveillance suffice but they fall short of their true potential. Incorporation of evolutionary data and analysis through studies such as phylogeography could reveal geographic sources of variation. Identification and targeting of such sources for public health initiatives could yield increased effectiveness of influenza treatments. As it stands there is a lack of evolutionary data available for such use, particularly in the southwest. Our study focused on the sequencing and phylogeography of southwestern Influenza A samples from the Mayo Clinic. We fully sequenced two neuraminidase genes and combined them with archived sequence data from the Influenza Research Database. Using RAxML we identified the clade containing our sequences and performed a phylogeographic analysis using ZooPhy. The resultant data were analyzed using programs such as SPREAD and Tracer. Our results show that the southwest sequences emerged from California and the ancestral root of the clade came from New York. Our Bayesian maximum clade credibility (MCC) tree data and SPREAD analysis implicates California as a source of influenza variation in the United States. This study demonstrates that phylogeography is a viable tool to incorporate evolutionary data into existing forms of influenza surveillance.
ContributorsTurnock, Adam Ryan (Author) / Scotch, Matthew (Thesis director) / Halden, Rolf (Committee member) / Pycke, Benny (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)
Created2013-05
Description
With global warming becoming a more serious problem and mankind's alarming dependency on fossil fuels, the need for a sustainable and environmentally friendly fuel source is becoming more important. Biofuels produced from photosynthetic microorganisms like algae or cyanobacteria offer a carbon neutral replacement for petroleum fuel sources; however, with the technology and information available today, the amount of biomass that would need to be produced is not economically feasible. In this work, I examined a possible factor impacting the growth of a model cyanobacterium, Synechocystis sp. PCC6803, which is heterotrophic bacteria communities accompanying the cyanobacteria. I experimented with three variables: the type of heterotrophic bacteria strain, the initial concentration of heterotrophic bacteria, and the addition of a carbon source (glucose) to the culture. With experimental information, I identified if given conditions would increase Synechocystis growth and thus increase the yield of biomass. I found that under non-limiting growth conditions, heterotrophic bacteria do not significantly affect the growth of Synechocystis or the corresponding biomass yield. The initial concentration of heterotrophic bacteria and the added glucose also did not affect the growth of Synechocystis. I did see some nutrient recycling from the heterotrophic bacteria as the phosphate levels in the growth medium were depleted, which was apparent from prolonged growth phase and higher levels of reactive phosphate in the media.
ContributorsCahill, Brendan Robert (Author) / Rittmann, Bruce (Thesis director) / Krajmalnik-Brown, Rosa (Committee member) / W. P. Carey School of Business (Contributor) / Chemical Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2015-12