<p>Dibenzothiophene (DBT) is a constituent of creosote and petroleum waste contamination, it is a model compound for more complex thiophenes, and its degradation by mixed microbial communities has received little attention. The chemical characteristics, environmental fate and ecotoxicology of DBT degradation products are not well understood. This research investigated DBT degradation in an enrichment culture derived from creosote-contaminated estuarian sediment using a suite of assays to monitor bacterial populations, bacterial growth, degradation products, DBT loss, and toxicity. Ultraviolet (UV) irradiation was evaluated as a sequential treatment following biodegradation. Additionally, to advance SYBR-Green qPCR methodology for characterizing mixed microbial communities, an alternative approach for evaluating qPCR data using a sigmoidal model to fit the amplification curve was compared to the conventional approach in artificial mixed communities. The overall objective of this research was to gain a comprehensive understanding of the degradation of a model heterocyclic PAH, DBT, by a mixed microbial community, particularly within the context of remediation goals.</p><p>DBT biodegradation was evaluated in laboratory scale cultures with and without pH control. The microbial community was monitored with 10 primer sets using SYBR-Green quantitative polymerase chain reaction (qPCR). Twenty-seven degradation products were identified by gas chromatography and mass spectrometry (GC/MS). The diversity of these products indicated that multiple pathways functioned in the community. DBT degradation appeared inhibited under acidic conditions. Toxicity to bioluminescent bacteria <italic>Vibrio fischeri</italic> more than doubled in the first few days of degradation, was never reduced below initial levels, and was attributed in part to one or more degradation products. UV treatment following biodegradation was explored using a monochromatic (254 nm) low-pressure UV lamp. While DBT was not extensively photooxidized, several biodegradation products were susceptible to UV treatment. At higher doses, UV treatment following DBT biodegradation exacerbated cardiac defects in <italic>Fundulus heteroclitus</italic> embryos, but slightly reduced toxicity to <italic>V. fischeri</italic>.</p><p>This research provides a uniquely comprehensive view of the DBT degradation process, identifying bacterial populations previously unassociated with PAH biodegradation, as well as potentially hazardous products that may form during biodegradation. Additionally, this research contributes to development of unconventional remediation strategies combining microbial degradation with subsequent UV treatment.</p> / Dissertation

Petroleum hydrocarbons are the most widespread contaminants in the environment. Interest in the biodegradation of polycyclic aromatic hydrocarbons and compounds (PAHs/PACs) is motivated by their ubiquitous distribution, their low bioavailability, high persistence in soils and their potentially deleterious effects to human health. Identifying the diversity of microorganisms that degrade PAHs/PACs can be utilised in the development of bioremediation techniques. Understanding the mechanisms of bacterial populations to adapt to the presence of pollutants and the extent that lateral transfer of key functional genes occurs, will allow the exploitation of microbial PAC/PAH-degradative capabilities and therefore enhance the successful application of bioremediation strategies. A key aim of this study was to isolate and identify PAC-degrading bacteria for potential use in future bioremediation programmes. A series of PAC enrichments were established under the same experimental conditions from a single sediment sample taken from a highly polluted estuarine site. Distinct microbial community shifts were directly attributable to enrichment with different PAC substrates. The findings of this study demonstrate that five divisions of the Proteobacteria and Actinobacteria can degrade PACs. By determining the precise identity of the PAC-degrading bacteria isolated, and by comparing these with previously published research, this study showed how bacteria with similar PAC degrading capabilities and 16S rRNA signatures are found in similarly polluted environments in geographically very distant locations e.g. China, Italy, Japan and Hawaii. Such a finding suggests that geographical barriers do not limit the distribution of key PAC-degrading bacteria. This is significant when considering the diversity and global distribution of microbes with PAC-degradative capabilities and the potential for utilising these microbial populations in future bioremediation strategies. In the laboratory, enrichment of bacteria able to utilise PAHs has commonly been performed in liquid media, with the PAH dissolved in a carrier solvent. This study found the presence of a carrier solvent significantly affects the resultant microbial population. Although the same sediment sample was used as the bacterial source in all enrichments, different bacterial strains were obtained depending upon the presence of the carrier solvent and the PAH. This is important when considering appropriate methodology for the isolation of PAH-degrading bacteria for future bioremediation programmes. Additionally, the species comprising the resultant population of the enrichment when a carrier solvent was present were similar to previously reported PAH-degrading species. Such a finding necessitates review of previously reported PAH-degrading bacterial species that have been isolated and identified from enrichments using a carrier solvent. Understanding how bacteria acclimatise to environmental pollutants is vital for exploiting these mechanisms within clear up strategies of contaminated sites. Two major lineages of the α subunit of PAH dioxygenases were identified: Actinobacteria and Proteobacteria. Comparison of the α subunit phylogeny with the 16S rRNA phylogeny implies that the PAH-dioxygenases evolved prior to the separation of these phyla or that lateral transfer occurred in the very distant past. No evidence for lateral transfer of the α subunit between the Actinobacteria and Proteobacteria was found in the phylogenetic analyses of this research. Multiple lateral transfer events were inferred between the species of the Actinobacteria and between the classes of the Proteobacteria. The clustering of the taxa within the α subunit phylogeny indicates that lateral transfer of the α subunit gene occurred after the separation of the classes of Proteobacteria and also after the speciation of the γ-Proteobacteria. These findings reveal how bacteria have acclimatised to PAH pollutants through multiple lateral transfer events of a key PAH-degradative gene. This knowledge of the transfer of genetic material will broaden our prospects of exploiting microbial populations.

All fossil fuels contain varying levels of sulfur compounds which are undesirable because they cause environmental pollution, corrosion, acid rain and lead to health problems. There is strict international legislation for the permissible levels of sulfur compounds in fossil fuels. The aim of this research therefore was the biocatalyst development for biodesulfurisation using two approaches. In the first approach, Rhodococcus erythropolis IGTS8-5 and IGTS8-5G were immobilised in porous coke particles and tested in repeated cycles successfully. Both bacterial strains grew well in the chemically defined medium with glucose as the main carbon and energy source and the model sulfur compound dibenzothiophene (DBT) as the sole sulfur source. 0.8 g of cells was immobilized on 250 g of coke particles without refreshing the medium over 72 h while 1.8 g of cells were immobilised on 250 g of coke when the media was refreshed every 24 hours for 120 h after the initial immobilisation batch of 72h. The latter, were used repeatedly in twelve consequtive batch desulfurisation cycles during which the biodesulfurisation activity progressively decreased from over 95% removal of 100 ppm DBT to around 45% removal. DBT removal is often expressed in terms of 2-hydroxybiphenyl which is the end product of biodesulfurisation. The biodesulfurisation activityof immobilised bacteria was equivalent to 310 umol 2-HBP h-1g-1 dry cell weight during the first hour. Freely suspended cells on the other hand exhibited biodesulfurisation activity equivalent to 91 umol 2-HBP h-1g-1 dry cell weight. Unfortunately, after the first 24 h, the activity of the immobilised cells decreased to 12 umol 2-HBP h-1g-1 dry cell weight. Use of plant cell cultures for biodesulfurisation is the other novel aspect of this work. Armoracia rusticana (horse radish) cell culture was chosen as the novel biocatalyst since this plant is a well known source of peroxidase enzyme which is involved in the biodesulfurisation metabolism according to the literature on bacterial biodesulfurisation. Arabidospsis thaliana (thale cress) was also used since its genome is completely sequenced and it is a model organism in genomics studies. Our results indicate that cell suspensions of both plants did show biodesulfurisation activity by reducing the level of sulfur compounds, mainly DBT and other three derivatives from both aqueous and oil phase. When compared to the bacteria, in terms of DBT consumption, the activity of A. rusticana was calculated as 55 umol DBT h-1 g-1 DCW and 65 umol DBT h-1 g-1 DCW for A. thaliana while in bacteria it was 91 umol DBT h-1 g-1 DCW for IGTS8-5 and 73 umol DBT h-1 g-1 DCW for IGTS8-5G. Transcriptomics analysis of the plant cell cultures after exposure to the DBT when compared to control cultures showed alterations in gene expression levels several of which were related to sulfur metabolism and transmembrane transporters of sulfate.

Heavy oil derived from oil sands is becoming an important resource of energy and transportation fuels due to the depletion of conventional oil resources. However, bitumen and heavy oils have a low hydrogen/carbon ratio and contain a large percentage of sulfur and nitrogen heterocyclic compounds. At the level of deep desulfurization, aromatic poly-nuclear molecules, especially nitrogen-containing heterocyclic compounds, exhibit strong inhibitive effect on hydrodesulfurization (HDS) due to competitive adsorption on catalytically active sites with sulfur-containing molecules. Therefore, it is necessary to study the HDS of refractory sulfur-containing compounds and also the effect of nitrogen-containing species on the deep HDS for achieving the ultra low sulfur specifications for transportation fuels. Additionally, the cost of H2 increased in recent years and a bitumen emulsion upgrading technique using an alternative in-situ H2 generated via the water gas shift (WGS) reaction during the hydro-treating was developed in our group. In the present study, a kind of nano-dispersed unsupported MoSx based catalyst was developed and used for hydrodesulfurization, hydrodenitrogenation (HDN) and upgrading bitumen emulsions. Objectives of this thesis were to (1) improve the catalytic activity of the nano-dispersed Mo based catalysts towards the HDS and HDN reactions of refractory sulfur-/nitrogen-containing compounds; and (2) compare the reactivity of in-situ hydrogen generated via the WGS reaction versus externally provided molecular hydrogen in HDS and HDN reactions to improve the efficiency of the bitumen emulsion upgrading technology developed by our group. In the present study, to stimulate the reaction system of bitumen emulsion, water was added into the organic reaction system, so there are different phases in this reaction system. To investigate the activity of the catalyst, the catalyst particles dispersed in different phases were characterized separatedly via HRTEM-EDX. After HRTEM-EDX study, all phases were mixed up and dried for further characterizations, BET, SEM, and XRD. The catalyst prepared in in-situ hydrogen was found to have higher surface area and smaller particle size than the one made in molecular hydrogen. The presence of sulfur-/nitrogen-containing compounds in the preparation system caused significant changes in the morphology of dispersed Mo sulfide catalyst according to HRTEM observations. Refractory sulfur-containing compounds of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) were used as model compounds in HDS studies. The simultaneous HDS of both model compounds was performed at different reaction temperatures from 330??C to 400??C. The effect of the reaction temperature on the WGS reaction in the presence of sulfur-containing model compounds was reported. A kinetic model for HDS reactions was proposed and used in discussing experiment results. The relative HDS reactivity of 4,6-DMDBT to DBT using dispersed Mo sulfide catalyst in in-situ hydrogen was found to be higher than the reported results which were obtained over supported catalysts. Nickel and potassium were introduced into Mo sulfide catalysts as promoters and their effect on the WGS reaction and the HDS reaction were discussed. The simultaneous HDS was carried out in the two different hydrogen sources. The in-situ hydrogen reaction system showed higher conversion and desulfurization results of both sulfur model compounds. This observation has been found to be mainly contributed by the higher activity of the Mo sulfide catalyst prepared in in-situ H2. Strong inhibitive effect of nitrogen-containing compounds, basic quinoline or non-basic carbazole, on the HDS of refractory sulfur model compounds was observed and discussed. Basic quinoline was a much stronger inhibitor than non-basic carbazole. The two HDS reaction pathways were affected by nitrogen-containing compounds to different extents. The HDN of quinoline over the dispersed Mo sulfide catalyst using in-situ hydrogen had been studied extensively by a previous member in our group. In this thesis, the HDN of carbazole was studied. From the identification of HDN products of carbazole, a HDN reaction network was proposed. The HDN of carbazole was processed at different reaction temperatures. The WGS reaction was not inhibited in the presence of carbazole. Comparable reactivity of the two hydrogen sources towards the HDN of carbazole was observed. The presence of 4,6-DMDBT caused significant effect on the HDN of carbazole due to the competitive adsorption on the catalyst surface.

M. Tech (Department of Chemistry, Faculty of Applied and Computer Sciences) Vaal University of Technology. / The presence of tires in open fields, households and landfills is a great threat to the wellbeing of the ecosystem around them. Tire creates an ideal breeding ground for disease carrying vermins and their possible ignition threatens the surrounding air quality due to the harmful gases produced during combustion. Pyrolysis of tires produces four valuable products namely; char, steel, tire pyrolytic oil (TPO) and noncondensable gases. TPO has been reported to have similar properties to commercial diesel fuel. The biggest challenge faced by TPO to be used directly in combustion engines is the available sulfur content of about 1.0% wt. Considering the stringent regulations globally for allowable sulfur content in liquid fuels, TPO therefore, requires deep desulfurization before commercialization. In this study, different desulfurization techniques were applied to reduce the sulfur content in TPO. A novel study on combination of adsorptive and air-assisted oxidative desulfurization (AAOD) was developed for desulfurization of TPO. Different carbon materials were employed as catalyst and/or adsorbent for the AAOD system. The effect of operating conditions; catalyst/adsorbent dosage, H2O2/HCOOH ratio, reaction time, temperature and air flowrate were studied. Oxidation equilibrium was reached at 80 °C for both commercial activated carbon (CAC) and activated tire char (ATC) at a reaction time of 50 min. With a total oil recovery of more than 90% and the initial sulfur content of 7767.7 ppmw, the presence of air at a flow rate of 60 l/hr increased oxidation from 59.2% to 64.2% and 47.4% to 53% for CAC and ATC, respectively. The use π-complexation sorbent was also applied to study the selectivity of such sorbents to organosulfur compounds (OSC) found in liquid fuels. The π-complexationbased adsorbent was obtained by ion exchanging Y-zeolite with Cu+ cation using liquid phase ion exchange (LPIE). Batch adsorption experiments were carried out in borosilicate beakers filled with modified Cu(I)-Y zeolite for both TPO and synthesized model fuels. For model fuels (MF), the selectivity for adsorption of sulfur compounds followed the order dibenzothiophene (DBT)> benzothiophene (BT)> Thiophene.

Yes / In this work, the performance of oxidative desulfurization (ODS) of dibenzothiophene (DBT) in light gas oil (LGO) is evaluated with a homemade manganese oxide (MnO2/γ-Al2O3) catalyst. The catalyst is prepared by Incipient Wetness Impregnation (IWI) method with air under moderate operating conditions. The effect of different reaction parameters such as reaction temperature, liquid hour space velocity and initial concentration of DBT are also investigated experimentally. Developing a detailed and a validated trickle bed reactor (TBR) process model that can be employed for design and optimization of the ODS process, it is important to develop kinetic models for the relevant reactions with high accuracy. Best kinetic model for the ODS process taking into account hydrodynamic factors (mainly, catalyst effectiveness factor, catalyst wetting efficiency and internal diffusion) and the physical properties affecting the oxidation process is developed utilizing data from pilot plant experiments. An optimization technique based upon the minimization of the sum of the squared error between the experimental and predicted composition of oxidation process is used to determine the best parameters of the kinetic models. The predicted product conversion showed very good agreement with the experimental data for a wide range of the operating condition with absolute average errors less than 5%.

Type 2 diabetes (T2D) is characterized by impaired beta cell function. The generation of various types of cellular stresses, including oxidative stress and ER stress, and the induction of cellular senescence can contribute to beta cell dysfunction. Recent studies have demonstrated associations between petrochemical exposure and beta cell dysfunction, particularly through induction of cellular stress. One class of compounds, commonly found in crude oil, are sulphur-containing heterocyclic aromatic compounds (S-HACs). S-HACs have been previously demonstrated to induce cellular stress in mammalian cells. This thesis aims to determine if S-HACs can induce cellular stress in beta cells and, consequently, impair beta cell function, particularly insulin production. Rat pancreatic beta cells, INS-1Es, were treated with two commonly occurring S-HACs, BNT(2,3D) and DBT, at doses which reflect non-occupational exposure levels. Upon treatment, various functional assays and qPCR experiments were performed for examining glucose uptake, ROS production, cellular senescence, ER stress and intracellular insulin production. It was observed that both BNT(2,3D) and DBT significantly increased glucose uptake and ROS production in the beta cells and upregulated the mRNA expression of various ER stress markers. In addition, BNT(2,3D) also induced cellular senescence, likely through a p53-independent pathway. This suggests that S-HACs may induce oxidative stress and ER stress in exposed beta cells, and some S-HACs may cause irreversible cell cycle arrest in response to these cellular stresses. However, intracellular insulin content in the INS-1Es was not altered by exposure to either S-HAC, suggesting that S-HACs may not impair insulin production. Nevertheless, the significant accumulation of ROS in S-HAC-exposed beta cells and the subsequent induction of cellular senescence by some S-HACs may alter other important beta cell functions, including mitochondrial function and insulin secretion, which could lead to the development of T2D; suggesting the potential for S-HACs to be novel beta cell toxicants. / Thesis / Master of Science (MSc)

Biodesulfurization (BDS) is an alternative to hydrodesulfurization (HDS) as a method to remove sulfur from crude oil. Dibenzothiophene (DBT) was chosen as a model compound for the forms of thiophenic sulfur found in fossil fuels; up to 70% of the sulfur in petroleum is found as DBT and substituted DBTs; these compounds are however particularly recalcitrant to hydrodesulfurization, the current standard industrial method. My thesis deals with enhancing BDS through novel strains and through nanotechnology. Chapter highlights are: Chapter 2. My first aim was to isolate novel aerobic, mesophilic bacteria that can grow in mineral media at neutral pH value with DBT as the sole sulfur source. Different natural sites in Iran were sampled and I enriched, isolated and purified such bacteria. Twenty four isolates were obtained that could utilize sulfur compounds. Five of them were shown to convert DBT into HBP. After preliminary characterization, the five isolates were sent to the Durmishidze Institute of Biotechnology in Tbilisi for help with strain identification. Two isolates (F2 and F4) were identified as Pseudomonas strains, F1 was a Flavobacterium and F3 belonged to the strain of Rhodococcus. The definite identification of isolate F5 was not successful but with high probability it was a known strain. Since no new strains were apparently discovered, I did not work further in this direction. Chapter 3. In a second approach I studied the desulfurization ability of Shewanella putrefaciens strain NCIMB 8768, because in a previous investigation carried out at Cranfield University, it had been found that it reduced sulfur odour in clay. I compared its biodesulfurization activity profile with that of the widely studied Rhodococcus erythropolis strain IGTS8. However, S. putrefaciens was not as good as R. erythropolis. Chapter 4 and 5. I then turned to nanotechnology, which as a revolutionary new technological platform offers hope to solve many problems. There is currently a trend toward the increasing use of nanotechnology in industry because of its potentially revolutionary paths to innovation. I then asked how nanotechnology can contribute to enhancing the presently poor efficiency of biodesulfurization. Perhaps the most problematic difficulty is how to separate the microorganisms at the end of the desulfurization process. To make BDS more amenable, I explored the use of nanotechnology to magnetize biodesulfurizing bacteria. In other words, to render desulfurizing bacteria magnetic, I made them magnetic by decorating their outer surfaces with magnetic nanoparticles, allowing them to be separated using an external magnet. I used the best known desulfurizing bacterial strain, Rhodococcus erythropolis IGTS8. The decoration and magnetic separation worked very well. Unexpectedly, I found that the decorated cells had a 56% higher desulfurization activity compared to the nondecorated cells. I proposed that this is due to permeabilization of the bacterial membrane, facilitating the entry and exit of reactant and product respectively. Supporting evidence for enhanced permeabilization was obtained by Dr Pavel Grigoriev, Institute of Cell Biophysics, Russian Academy of Sciences, Pushchino. In Chapter 6, to optimize attachment of the nanoparticles to the surface of the bacteria I created thin magnetic nanofilms from the nanoparticles and measured the attachment of the bacteria using a uniquely powerful noninvasive optical technique (Optical Waveguide Lightmode Spectroscopy, OWLS) to quantify the attachment and determine how the liquid medium and other factors influence the process.

Ein vielversprechendes Design für organische lichtemittierende Dioden (OLEDs) verwendet eine Wirt-Gast-Strategie durch Dispergieren einer kleinen Menge eines hocheffizienten Emitters (der Gast) in eine passende Transportmatrix (der Wirt). Die Aufgabe des Wirts ist den Exzitonentranport zum Emitter sicherzustellen und den Zerfall von Triplet-Exzitonen zu verhindern, und damit eine hohe Bauteilperformance zu erreichen. Die vorliegende Arbeit konzentriert sich auf die Beziehung zwischen Molekülstruktur und optoelektrischer Eigenschaften von Carbazol/Dibenzothiophen-Derivaten. Die Untersuchung umfasst sieben dieser Derivate für den Wirt, bei denen die Carbazoleinheit als Donator und die Dibenzothiopheneinheit als Akzeptor fungiert, wobei beide durch einen oder mehrere Phenylabstandshalter verbunden sind. Diese Wahl der Wirtsmaterialien erlaubt es den Einfluss der erweiterten Phenylabstandshalter und der unterschiedlichen molaren Verhältnisse von Akzeptor zu Donator zu untersuchen. Es ergab sich, dass eine kürzere Phenylabstandshalterlänge die Bauteilperformance durch eine größere Löcher- und Elektronendichte in der Emitterschicht verbessert; und ein 1:1 Carbazol-zu-Dibenzothiophen-Verhältnis der Bauteilperformance zuträglich ist, da es zu einem Ladungsträgergleichgewicht in der Emitterschicht führt. Diese Arbeit zeigt, unter Verwendung dieser Wirtsmaterialien, blaue FIrpic-basierte phosphoreszierende OLEDs (PhOLEDs) und grüne 4CzIPN-basierte thermisch aktivierte verzögerte Phosphoreszenz (TADF) OLEDs. Die blauen PhOLEDs und grünen TADF OLEDs mit mDCP zeigten Effizienzen von 43 cd/A (18.6%) beziehungsweise 66 cd/A (21%). / A particularly interesting organic light-emitting diodes (OLEDs) design adopts a host-guest strategy by dispersing a small amount of highly efficient emitter (the guest) into an appropriate transport matrix (the host). The host is utilized to transfer excitons to the emitter and to prevent triplet exciton quenching, thus high device performance can be achieved. The present thesis focuses on the relationship between the molecular structure and opto-electrical properties of carbazole/dibenzothiophene derivatives. The investigation encompasses seven of these derivatives for the host, in which the carbazole unit acts as a donor and the dibenzothiophene as an acceptor while they are linked through phenyl spacer(s). This choice of host materials enables to assess the impact of extended phenyl spacers and different acceptor to donor molar ratios. It was found that decreasing the phenyl spacer length enhances the device performance due to the larger both hole and electron densities in the emitting layer; and a 1:1 carbazole to dibenzothiophene ratio is favorable for device performance, since it balances the charge carriers in the emitting layer. Using these host materials, the work presented in this thesis demonstrates high-performance blue FIrpic-based phosphorescent OLEDs (PhOLEDs) and green 4CzIPN-based thermally activated delayed fluorescence (TADF) OLEDs. The blue PhOLEDs and green TADF OLEDs with mDCP showed efficiencies of 43 cd/A (18.6%) and 66 cd/A (21%), respectively.