Bacterial quorum sensing is regarded as a novel target for the design of antimicrobials. Based on lead structures identified from HTS, 39 analogues have been synthesized and evaluated in Vibrio haveyi. Potent inhibitors with IC50 values at single-digit micromolar concentrations for AI-2 mediated quorum sensing have been identified. On the second project, post-synthesis modifications of DNA provide easy functionalizations for expanded applications such as aptamer selection. A CBT-modified thymidine analogue (CBT-TTP) has been synthesized and used for enzymatic incorporation into DNA. Post-synthesis modifications through condensation with 1,2-aminothiol for installation of a boronic acid moiety or a fluorophore have been achieved. On the third project, H2S has been recognized as an important gasotransmitter and its concentration is relevant to a variety of diseases. A novel fluorescent probe (DNS-Az) has been developed for quantitation of H2S in aqueous solutions. This probe has been used to measure H2S concentrations in the blood.

Abstract Hydrogen sulfide (H2S) is an environmentally hazardous, corrosive, and toxic gas, mostly generated in gas and oil industry. For small-scale natural gas processing sites (less than 10 tonne S/day), the use of regenerable iron oxide adsorbent to adsorb H2S from natural gas is still an economical and effective method. The objective of this research project was to understand the performance of an iron oxide adsorbent, recently emerging in the Canadian market, in removing H2S from gas streams. To accomplish this, the breakthrough behaviors of H2S adsorption in a fixed-bed reactor under elevated pressures were studied. The effects of variations in superficial velocity from 0.09 m/s to 0.26 m/s, operating pressure from 4 to 50 atm absolute, and the height of the fixed-bed from 11.7 cm to 24.5 cm on breakthrough curves and sulfur loading were investigated. In all the experiments, the H2S concentration profiles of the exiting gas from the reactor were measured until the bed was saturated. It was found that the shape of the breakthrough curves depend on the superficial velocity and the inlet H2S concentration in gas streams. Under both higher superficial velocity and higher inlet H2S concentration, the shape of the breakthrough curve becomes steeper. The sulfur loading of the adsorbent depends on the superficial velocity, the inlet H2S concentration in gas streams, and the bed height. The sulfur loading decreases as the superficial velocity and the inlet H2S concentration increase, but increases as the bed height increases. The change of operating pressure does not have a significant effect on the shape of the breakthrough curve or sulfur loading of the adsorbent. The investigation was also extended using the regenerated adsorbents. A mathematical formula was developed to describe the breakthrough curves.

This dissertation consists of two parts on the treatment of hydrogen sulfide and odorants in gases emitted from rubber processing industry. In the first part, we study performance of removal hydrogen sulfide with bioscrubber. An activated sludge aeration tank (W ¡Ñ L ¡Ñ H = 0.40 ¡Ñ 0.40 ¡Ñ 3.00 m) with a 2 mm-orifice air sparger was used to treat gaseous hydrogen sulfide (H2S). The investigation tested the operational stability as well as how the removal ability of H2S was affected by influent H2S concentration (C0 = 50-900 ppm), aeration intensity (Q/V = 0.083-0.50 m3 m-3 min-1), liquid depth (H = 0.5-3.0 m), and mixed-liquor suspended solids concentration (MLSS = 970-2,800 mg L-1). Experimental results indicate that H2S removal efficiencies of 96% and over 98% were obtained with H = 0.5 m and H > 1.0 m in the cited operation conditions, respectively. Experimental results also indicate no sludge bulking problem occurred with total sulfide loadings of 0.047-0.148 kg S kg-1 MLSS d-1. The second part aimed at the removal of odorous compounds in gases emitted from rubber processing industries. Simulated odorous gas for test was prepared by mixing fresh air and an odorous gas drawn from an oven in which a sample of rubber powder was kept either at 160¢XC (for a thermal plastic rubber) or 200¢XC (for a thermal setting rubber). The prepared odorous gas was then premixed with a definite amount of ozone-enriched air and introduced into a contact system. The contact system consists of two sieve-plate columns connected in series and each column has four 1-L chambers. Depending on with or without introducing circulating scrubbing water into the columns, the oxidation reaction could be either wet or dry one. Results indicate the wet oxidation got better performances than the dry one. The former got 97 and over 90% removal of VOCs (volatile organic compounds) and odorous intensity removal, respectively, with the operation conditions of initial ozone concentration 4.0 ppm, THC (total hydrocarbon) concentrations 6.5¡V10.3 ppm (methane equivalent), oxidation temperature 37.3¢XC, gas empty bed retention time (EBRT) 12 s, and liquid/gas rate ratio 0.01 m3/m3. With conditions similar to those cited above, odor concentration (dilutions to the threshold, D/T) in the test gas could be reduced from 1,738¡V3,090 to 31¡V98 with EBRTs of 11.4¡V14.5 s. Activated carbon is effective for both physical and chemical removals of residual VOCs, odorous compounds, and ozone in the effluent gas from the ozonation system. Economical analysis indicates that around US$ 0.16 is required for treating 1,000 m3 of the tested foul gas by the proposed ozonation process.

Thesis (Ph. D.)--Institute of Paper Chemistry, 1966. / Includes bibliographical references (p. 114-117).

Reservoir souring refers to the increase in the concentration of hydrogen sulfide in production fluids during waterflooding. Besides health and safety issues, H₂S content reduces the value of the produced hydrocarbon. Nitrate injection is an effective method to prevent the formation of H₂S. Although the effectiveness of nitrate injection has been proven in laboratory and field applications and biology is well-understood, modeling aspect is still in its early stages. This work describes the modeling and simulation of biological reactions associated with reservoir souring and nitrate injection for souring remediation. The model is implemented in a general purpose adaptive reservoir simulator (GPAS). We also developed a physical dispersion model in GPAS to study the effect of dispersion on reservoir souring. The basic mechanism in the biologically mediated generation of H₂S is the reaction between sulfate and organic compounds in the presence of sulfate-reducing bacteria (SRB). Several mechanisms describe the effect of nitrate injection on reservoir souring. We developed mathematical models for biological reactions to simulate each mechanism. For every biological reaction, we solve a set of ordinary differential equations along with differential equations for the transport of chemical and biological species. Souring reactions occur in the areas of the reservoir where all of the required chemical and biological species are available. Therefore, dispersion affects the extent of reservoir souring as transport of aqueous phase components and the formation of mixing zones depends on dispersive characteristics of porous media. We successfully simulated laboratory experiments in batch reactors and sand-packed column reactors to verify our model development. The results from simulation of laboratory experiments are used to find the input parameters for field-scale simulations. We also examined the effect of dispersion on reservoir souring for different compositions of injection and formation water. Dispersion effects are significant when injection water does not contain sufficient organic compounds and reactions occur in the mixing zone between injection water and formation water. With a comprehensive biological model and robust and accurate flow simulation capabilities, GPAS can predict the onset of reservoir souring and the effectiveness of nitrate injection and facilitate the design of the process. / text

No description available.

BspA was first identified on the basis of being the major constituent of 5 M LiCl washes of whole Lactobacillus fermentum BR11 cells. The bspA gene is encoded within a putative ATP-binding cassette (ABC) transport operon, and sequence analysis revealed that it is a member of the family III solute binding proteins. Unlike the majority of solute binding proteins from Gram-positive bacteria, BspA is not tethered to a lipid anchor in the cell membrane, and hence is not a lipoprotein. Extraction of BspA with concentrated salt solutions such as 5 M LiCl is consistent with the notion that electrostatic interactions are responsible for securing it to the L. fermentum BR11 cell. L. fermentum PNG201 is a BspA negative mutant strain created by disrupting bspA. This strain was shown to be incapable of cystine uptake. Thus, the genetic and biochemical evidence strongly suggests BspA is a cystine binding protein of an ABC transporter. Measurement of the binding affinity between BspA and L-cystine has confirmed high affinity binding (dissociation constant is 0.2 µM), and high specificity (over 100-fold excess of non-target amino acids did not disrupt BspA / L-cystine binding). In addition, collagen did not appear to affect BspA/cystine binding, indicating extracellular matrix (ECM) binding capacity noted by other researchers may be unrelated to amino acid binding. An interesting phenotypic characteristic of L. fermentum PNG201 is its apparent increased sensitivity to oxygen and the superoxide-generating chemical - paraquat compared to the parent L. fermentum BR11 strain. Catalase supplemented aerobic cultures of L. fermentum BR11, and L. fermentum PNG201 were protected from oxidative stress, suggesting hydrogen peroxide is responsible for the observed oxidative stress. It was found that addition of cystine to aerobic cultures of L. fermentum BR11 or L. fermentum PNG201 protected both strains from oxidative stress, with L. fermentum BR11 able to utilize smaller concentrations of cystine compared to L. fermentum PNG201. Detection of hydrogen peroxide in aerobic cultures of L. fermentum BR11 and L. fermentum PNG201 confirmed the production of hydrogen peroxide is responsible for causing oxidative stress. The BspA mutant strain L. fermentum PNG201 consistently produced more hydrogen peroxide per optical density compared with the wild type, indicating it overproduced hydrogen peroxide. When 0.4 mM hydrogen peroxide has been accumulated by growing cell cultures, both L. fermentum BR11 and L. fermentum PNG201 enters stationary phase, suggesting both strains have a similar sensitivity to hydrogen peroxide. Small epitopes from the HIV gp41 protein and the Chlamydia psittaci major outer membrane protein have been successfully displayed on the cell surface of L. fermentum BR11 as fusion proteins to the BspA molecule. However, the capability of BspA in exporting larger polypeptides has not been tested. In this study, the large extracellular enzyme - glucosyltransferase (GtfJ) from Streptococcus salivarius ATCC 25975 was fused to BspA to demonstrate that this expression system is capable of exporting large functional enzymes to the cell surface of L. fermentum BR11. The native GtfJ is 160kDa in size and also contained an export signal, which was deleted in the cloning process and replaced with BspA, resulting in a fusion protein of 175kDa. Export of the BspA/GtfJ fusion protein is dependant entirely on BspA's export signal. Recombinant enzyme expression and glucosyltransferase activity were detected by measuring the glucan formed by sonicated cell extracts in acrylamide gels. Enzyme activity measurements on whole cells has revealed the recombinant Lactobacillus was incorporating 20-40 nmol of sucrose-derived-glucose into glucan per ml of cell culture per OD unit, which is comparable to activity levels exhibited by the native bacteria that expressed this enzyme. Comparison of GtfJ enzyme activity between whole cells and sonicated cell extracts of recombinant L. fermentum confirmed the extracellular location of BspA/GtfJ as enzyme activity was essentially identical.

Dissertation (M.Sc. (Chemical engineering)) -- University of Pretoria, 2008. / Includes bibliographical references (p. 42-52)

Thesis (Ph.D.)--Ohio University, August, 2008. / Title from PDF t.p. Includes bibliographical references.

Thesis (Ph.D.)--Ohio University, November, 2006. / Title from PDF t.p. Includes bibliographical references.