Theses and Dissertations at Montana State University (MSU)
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Item Biocorrosion of copper by Oleidesulfovibrio alaskensis G20 biofilms in static and dynamic environments(Montana State University - Bozeman, College of Engineering, 2024) Keskin, Yagmur; Chairperson, Graduate Committee: Brent M. Peyton; Matthew Fields (co-chair); This is a manuscript style paper that includes co-authored chapters.This study presents a detailed examination of the intricate relationships between Oleidesulfovibrio alaskensis G20 and copper (101), emphasizing three interconnected perspectives: the kinetics of copper toxicity in three distinct media, the impact of surface finishing on microbiologically influenced corrosion (MIC), and the interaction of G20 biofilms and copper in CDC biofilm reactors. Initially, the study concentrates on the kinetic effects of copper toxicity on the growth of G20. The research meticulously quantifies the detrimental impact of different copper (II) concentrations (6, 12, 16, and 24 micron) on bacterial growth kinetics in three media: LS4D balanced (BAL), electron acceptor-limited (EAL), and electron donor-limited (EDL). Using a non-competitive inhibition model, I50 (concentrations of copper causing 50% inhibition of bacterial growth) values were calculated to be 13.1, 13.87, and 11.31 micron for LS4D BAL, EAL, and EDL media, respectively. The second part of the study shifts its focus to the effect of surface finishing on MIC of copper 101 by G20. The biofilm and corrosion pit depths were measured through a series of sophisticated analyses employing 3D optical profilometry, Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX), and X-ray Diffraction Analysis (XRD). The research investigates how different levels of surface roughness, applied through metallographic grinding and polishing, influence corrosion. The findings demonstrate a clear pattern of both uniform and pitting corrosion across all surface finishes. Notably, a statistically significant decrease in corrosion rates was observed when the surface roughness of copper was altered from approximately 13?m to about 0.06?m. Finally, the study explores the interaction between G20 biofilms and copper (101) into CDC reactors to understand biofilm development on copper surfaces and its subsequent impact on copper corrosion in a dynamic environment over periods of 7, 9, and 14 days. The results showed robust biofilm formation through hexose and protein analyses and SEM images displaying progressive increases in SRB cell accumulation over time. Localized pit depths were measured and compared to static conditions, and pits showed only a 20% increase in a dynamic environment. These findings offer an improved understanding of the complex interactions between G20 and MIC of copper.Item Biodegradable composite hydromulches for sustainable organic horticulture(Montana State University - Bozeman, College of Engineering, 2023) Durado, Andrew Dalton; Chairperson, Graduate Committee: Dilpreet S. BajwaIn agriculture, mulch helps retain soil moisture and temperature while preventing weed growth. The most common material used for commercial mulching is low-density polyethylene (LDPE). At the end of the growing season, this plastic is typically buried or burned, causing a negative impact on the environment. This project aims to develop an alternative to LDPE mulch that is acceptable for organic farming and biodegradable. The tested hydromulch (HM) treatments contain a mixture of paper pulp, wood fiber, or hemp hurds combined with a tackifier and water. The tackifiers evaluated were guar gum, psyllium husk, and camelina meal, at various concentrations. These treatments were tested for tensile strength, puncture resistance, rain fastness, density, soil adhesion, porosity, and C:N ratio. The results have shown that samples containing tackifiers outperformed the control that contained no tackifier in the strength tests but not in the rain fastness or soil adhesion tests. Paper was the best fibrous material and guar gum was the top performing tackifier. When tackifier blends were considered, an interaction between two tackifiers occurred resulting in a decrease in strength. Blends containing wood fiber and hemp hurds did not show promising results. The puncture resistance of all mulches significantly decreased at 50% moisture level regardless of tackifier type. Some formulations performed well and could be promising in future field trials. The next step will be to examine these formulations outdoors in large-scale field studies.Item Biochemical and biophysical characterization of plastic degrading aromatic polyesterases(Montana State University - Bozeman, College of Letters & Science, 2019) Topuzlu, Ece; Chairperson, Graduate Committee: Valerie Copie; Brandon C. Knott and Mark D. Allen were authors and Japheth Gado, Harry P. Austin, Erika Erickson, Bryon S. Donohoe, Nicholas A. Rorrer, Fiona L. Kearns, Graham Dominick, Christopher W. Johnson, Valerie Copie, Christina M. Payne, H. Lee Woodcock, Gregg T. Beckham and John E. McGeehan were co-authors of the article, 'Structural and biochemical characterization of MHETASE' submitted to the journal 'Proceedings of the National Academy of Sciences of the United States of America' which is contained within this dissertation.As the world is producing more plastics than it can recycle, accumulation of manmade polymers in the environment is becoming one of the greatest global threats humanity is facing today. One of the major contributors to the plastics pollution problem is polyethylene terephthalate (PET), an aromatic polyester widely used in the packaging, beverage, garment and carpeting industries. As a response to the onslaught of plastics in the environment, fungi and bacteria are evolving metabolic pathways to convert plastics into useable energy sources. One of these organisms, a bacterium, Ideonella sakaiensis 201-F6, has recently been identified to convert PET into its monomers, terephthalic acid (TPA) and ethylene glycol (EG), and to use these compounds for energy and growth. I. sakaiensis' ability to convert PET is made possible by two enzymes, named PETase and MHETase. As a first step, PETase breaks down the insoluble substrate PET into a soluble major hydrolysis product - mono-(2- hydroxyethyl) terephthalate (MHET), which is then further hydrolyzed by MHETase into TPA and EG. Crystal structure of PETase, as well as some of its biochemical features, have been reported several times to date, but MHETase has remained largely uncharacterized. This work focuses on further discovery-driven biophysical and biochemical characterization of PETase, visualization of PETase activity on various polyester surfaces, as well as the structural and biochemical characterizations of the MHETase enzyme. We have found that several aspects of PETase-mediated substrate surface modification hydrolysis mechanisms differ depending on the specific mechanical and material characteristics of the substrate. We have also found that PETase is inhibited by BHET. Additionally, we have solved the crystal structure of MHETase. MHETase consists of an alpha/beta hydrolase domain, and a 'lid' domain, commonly seen in lipases. Molecular dynamics simulations revealed the mechanism of MHETase action. Through bioinformatics approaches, we have also identified mutants of interest for improved MHETase activity. Coincubation of MHETase with PETase affects PET turnover in a synergistic fashion. Taken together, this work provides additional insights into the mechanisms of action of the PETase and MHETase enzymes, which may open new avenue for bioremediation and removing plastics from the environment in a sustainable manner.Item The implementation of municipal composting in the state of Montana(Montana State University - Bozeman, 1994) Jones, Brian Stanley; Chairperson, Graduate Committee: Kenneth L. BruwelheideItem Biocorrosion of 1018 steel in sulfide rich marine environments: a correlation between strain and corrosion using electron backscatter diffraction(Montana State University - Bozeman, College of Engineering, 2014) Martin, Joshua Daniel; Chairperson, Graduate Committee: Paul E. GannonMicrobially induced corrosion (MIC) of steel due to the presence of sulfide is a leading cause of pit formation of carbon steel in fuel-seawater environments. While extensively studied, the exact causes of pitting corrosion in naval fuel tanks when exposed to MIC in the presence of fuel and seawater are not completely understood. This thesis focuses on the role that cold-rolling of carbon steel plays on corrosion while subjected to sulfidogenic, suboxic corrosive environments. Particularly, the effects of microscopic residual strain found within 1018 steel on the anodic dissolution of the metal is studied in different MIC sulfide environments using EBSD, AFM, FE-SEM, EDX, and electrochemistry. It is found that regions of increased plastic deformation of the crystalline lattice as a result of cold rolling correlate to an increase in anodic dissolution rates of 1018 steel coupons cut parallel to rolling direction. Image overlay provides a verification of the location of corrosion of samples to the same locations found in EBSD mapping taken prior to corrosion, ensuring the predictive value of EBSD analysis in establishing locations of accelerated corrosion. The effect of different corrosion environments on the corrosion rate of steel is measured through electrochemistry. Values obtained through these measurements are applied using mechanochemical theories to predict the localized dissolution rate of the steel due to strain using computational methods. Mechanochemical analysis of the strained areas results in predicted corrosion rates within an order of magnitude of the corrosion rates measured using AFM for the exposed time period at the same locations. Areas exhibiting increased corrosion rates occur in areas exhibiting increased strain as measured by EBSD analysis. Further electrochemical results show an increase in corrosion rates for suboxic sulfide rich systems containing low levels of oxygen, when compared to anaerobic sulfide environments. Variations in corrosion current density as a function of oxygen presence, as measured by electrochemistry, accurately predict variations in mechanochemical corrosion rates of strained areas well within an order of magnitude. Results from this study support the use of EBSD as a means to further the understanding of pitting corrosion as a function of material properties.Item The soil adsorption, mobility, degradation, and residual properties of AC 222,293(Montana State University - Bozeman, College of Agriculture, 1987) Fellows, Gary MiltonItem Autohydrolysis and deligninfication of wheat straw(Montana State University - Bozeman, College of Engineering, 1985) Nakaoka, Ronald KurtItem Enhanced herbicide degradation and dissipation of clomazone in two Montana soils(Montana State University - Bozeman, College of Agriculture, 1988) Gallandt, Eric RobertItem Stability and expression of a plasmid-borne TCE degradative pathway in suspended and biofilm cultures(Montana State University - Bozeman, College of Engineering, 1995) Sharp, Robert Raymond, IIIItem Processes affecting solute transport through soils : preferential flow and microbial degradation(Montana State University - Bozeman, College of Agriculture, 1997) Langner, Heiko Walter
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