Microbial cell disruption using pressurized gas is a promising approach to improve the lipid extraction yield directly from the wet biomass by eliminating the energy-intensive drying process, which is an integral part of traditional methods. As the process starts with the solubilization of the gas in lipid-rich microbial cells, it is important to understand the solubility of different potential gases in both lipid (triglyceride) and lipid-rich microbial cell culture to design efficient cell disruption processes. In this study, we determined the solubility of different gases (e.g., CO2, CH4, N2, and Ar) in canola oil (triglyceride) using a pressure drop gas apparatus developed in our laboratory. The solubility of different gases in triglyceride followed the trend CO2 > CH4 > Ar > N2. Since the solubility of CO2 was found to be higher compared to other gases, the solubility of CO2 in lipid rich cell culture, cell culture media, and spent media was also determined. It was found that CO2 is more soluble in triglycerides, but less soluble in lipid-rich cell culture compared to CO2 in water. From both thermodynamic models and Monte Carlo simulations, the correlated solubility was found to be in good agreement with the experimental results. CO2 was found to be the most suitable gas for microbial cell disruption because almost 100% cell death occurred when using CO2 whereas more than 85% cells were found to be active after treatment with CH4, N2, and Ar. The optimization of microbial cell disruption was conducted using the combination of Box-Behnken design of experiment (DOE) technique and response surface methodology. The optimized cell disruption conditions were found to be 3900 kPa, 296.5 K, 360 min, and 325 rpm where almost 100% cell death was predicted from the statistical modeling. Finally, it was found that 86% of the total lipid content can be recovered from the wet biomass after treatment with pressurized CO2 under optimized conditions compared to control where up to 74% of the total lipid content can be recovered resulting in 12% increase in the lipid extraction yield using pressurized CO2.

This work focuses on the physical properties and crystallization of theophyline co-crystals. Co-crystals of theophylline with oxalic acid, glutaric acid and maleic acid have been investigated. The DSC curves of these co-crystals show that their first endothermic peaks are all lower than the melting temperature of theophylline. The decomposition temperature of theophylline – oxalic acid co-crystal is at about 230 °C, determined by DSC together with TGA. After decomposition, the remaining theophylline melts at about 279 °C, which is higher than the known melting temperature of theophylline, suggesting a structure difference, ie. a new polymorph may have been formed. The formation of hydrogen bonds in theophylline – oxalic acid co-crystal was investigated by FTIR. Changes of FTIR peaks around 3120 cm-1 reflects the hydrogen bond of basic N of theophylline and hydroxyl H of oxalic acid. The solubility of theophylline – oxalic acid co-crystal and theophylline – glutaric acid co-crystal was determined in 4:1 chlroform – methanol and in pure chloroform respectively. At equilibrium with the solid theophylline – oxalic acid co-crystal, the theophylline concentration is only 60 % of the corresponding value for the pure solid theophylline. At equilibrium with the solid theophylline – glutaric acid co-crystal, the theophylline concentration is at least 5 times higher than the corresponding value for the pure solid theophylline. Two phases of theophylline were found during the solubility determination. In the chloroform – methanol mixture (4:1 in volume ratio) the solubility of the stable polymorph of theophylline is found to be about 14 % lower than that of the metastable phase. Various aspects of the phase diagram of theophylline – oxalic acid co-crystal was explored. Theophylline – oxalic acid co-crystal has been successfully prepared via primary nucleation from a stoichiometric solution mixture of the two components in chloroform – methanol mixture. By slurry conversion crystallization, the co-crystal can be prepared in several solvents, and yield and productivity can be significantly increased. Theophylline – glutaric acid can be successfully prepared via both co-grinding of the two components and slow evaporation with seeding. / QC20100608

The aim of this work was to investigate and determine central parameters that can be used to control and increase the solubility, quality and productivity of recombinant proteins. These central parameters should be applicable under the constraints of high-throughput protein production in Escherichia coli. The present investigation shows that alternative methods exist to improve solubility, quality and productivity of the recombinant protein. The hypothesis is that by reducing the synthesis rate of the recombinant protein, a higher quality protein should be produced. The feed rate of glucose can be used to decrease the synthesis rate of the recombinant protein. The influence of feed rate on solubility and proteolysis was investigated using the lacUV5-promoter and two model proteins, Zb-MalE and Zb-MalE31. Zb-MalE31 is a mutated form of Zb-MalE that contains two different amino acids. These altered amino acids greatly affect the solubility of the protein. The soluble fraction is generally twice as high using Zb-MalE compared to Zb-MalE31. Using a low feed rate compared to high benefits the formation of the full-length soluble protein. Furthermore, by using a low feed rate, the proteolysis can be decreased. One other factor that influences the solubility is the amount of inducer used. An increase from 100 µM to 300 µM IPTG only results in more inclusion bodies being formed, the fraction of soluble protein is the same. The quality aspect of protein production was investigated for a secreted version of Zb-MalE using two different feed rates of glucose and the maltose induced promoter PmalK. It was shown that when the protein was secreted to the periplasm, the stringent response as well as the accumulation of acetic acid (even for high feed rates) was reduced. The stringent response and accumulation of acetic acid are factors that are known to affect the quality and quantity of recombinant proteins. Transporting the protein to the periplasm results in this case on a lower burden on the cell, which leads to less degradation products being formed when the protein is secreted to the periplasm. Seeing the feed rate as a critical parameter, the high-throughput production would benefit from a variation in the feed rate. However, since the fed-batch technique is technically complicated for small volumes another approach is needed. E.coli strains that have been mutated to create an internal growth limitation that simulate fed-batch were cultivated in batch and were compared to the parent strain. It was shown that the growth rate and acetic acid formation was comparable to the parent strain in fed-batch. Furthermore it was shown that a higher cell mass was reached using one of the mutants when the cells were cultivated for as long time as possible. The higher cell mass can be used to reach a higher total productivity. / QC 20101112

Indiana University-Purdue University Indianapolis (IUPUI) / The cementation procedure is the key to long-term success of fixed restorations. The prognosis of prosthetic restoration is largely impacted by the maintenance of the luting cement and the adhesive bond. When exposed to water or saliva, most restorative materials undergo hydrolytic degradation. The purpose of this study is to evaluate the water solubility and water sorption characteristics of newly introduced acidic polymeric luting agents over a 180-day water-storage period. Nine different luting agents were tested. Fifty-two disc specimens of each material were fabricated using a mold with an internal dimension of 15[plus-minus]0.1 mm in diameter and 1.0 [plus-minus]0.1 mm deep. A constant weight, W0 [subscript zero], was reached after desiccating the specimens. Then, 13 specimens were assigned randomly to one of the four testing periods in the water for seven, 30, 90 and 180 days. After each period, the specimens were removed from the water and weighed to get W1 [subscript one]. A second period of desiccating the samples provided a constant weight W2 [subscript two]. The water sorption and solubility were determined by the following equations: WSP [subscript SP](%) = (W1 [subscript one] W2 [subscript two] ) X 100/ W0 [subscript zero] ,WSL [subscript SL](%) = (W0 [subscript zero] W2 [subscript two) X 100/ W0 [subscript zero]. The resin-modified glass-ionomers showed the highest water sorption/solubility results. The resin luting agents had the lowest sorption/solubility results. The self-adhesives showed a wide range of solubility/sorption; in general, they showed lower results compared with the resin-modified glass-ionomers. All the materials reached some sort of equilibrium after 90-days. Based on the results of our study, we conclude that self-adhesive luting materials were not all alike. Rely X Unicem was the most comparable to the resin luting materials. The resin luting materials had the lowest solubility and sorption. Resin-modified glass-ionomers showed the highest sorption/solubility results.

In the production of biodiesel via the transesterification of vegetable oils, purification to international standards is challenging. A key measure of biodiesel quality is the level of free glycerol in the biodiesel. In order to remove glycerol from fatty acid methyl ester (FAME or biodiesel), a membrane separation setup was tested. The main objective of this thesis was to develop a membrane process for the separation of free glycerol dispersed in FAME after completion of the transesterification reaction and to investigate the effect of different factors on glycerol removal. These factors included membrane pore size, pressure, temperature, and methanol, soap and water content. First, a study of the effect of different materials present in the transesterification reaction, such as water, soap, and methanol, on the final free glycerol separation was performed using a modified polyacrylonitrile (PAN) membrane, with 100 kD (ultrafiltration) molecular weight cut off for all runs at 25°C. Results showed low concentrations of water had a considerable effect in removing glycerol from the FAME. The mechanism of separation of free glycerol from FAME was due to the removal of an ultrafine dispersed glycerol-rich phase present in the untreated (or raw) FAME. The size of the droplets and the free glycerol separation both increased with increasing water content of the FAME. Next, three types of polymeric membranes in the ultrafiltration range with different molecular weight cut off, were tested at three fixed operating pressures and three operating temperatures (0, 5 and 25oC) to remove the free glycerol from a biodiesel reactor effluent. The ASTM standard for free glycerol concentration was met for the experiments performed at 25°C. The results of this study indicate that glycerol could be separated from raw FAME to meet ASTM and EN standards at methanol feed concentrations of up to 3 mass%. The process was demonstrated to rely on the formation of a dynamic polar layer on the membrane surface. Ceramic membranes of different pore sizes (0.05 µm (ultrafiltration (UF) range) and 0.2 µm (microfiltration (MF) range)) were used to treat raw FAME directly using the membrane separation set up at temperatures of 0, 5 and 25°C. The results were encouraging for the 0.05 µm pore size membrane at the highest temperature (25°C). The effect of temperature on glycerol removal was evident from its relation with the concentration factor (CF). Higher temperatures promoted the achievement of the appropriate CF value sooner for faster separation. Membrane pore size was also found to affect separation performance. A subsequent study revealed the effect of different variables on the size of the glycerol droplets using dynamic light scattering (DLS). A key parameter in the use of membrane separation technology is the size of the glycerol droplets and the influence of other components such as water, methanol and soaps on that droplet size. The effect of water, methanol, soap and glycerol on the size of suspended glycerol droplets in FAME was studied using a 3-level Box-Behnken experimental design technique. Standard statistical analysis techniques revealed the significant effect of water and glycerol on increasing droplet size while methanol and soap served to reduce the droplet size. Finally, a study on the effect of trans-membrane pressure (TMP) at different water concentrations in the FAME phase on glycerol removal using UF (0.03 µm pore size, polyethersulfone (PES)) and MF (0.1 and 0.22 µm pore sizes, PES) membranes at 25, 40 and 60°C was performed. Results showed that running at 25°C for the two membrane types produced the best results for glycerol removal and exceeded the ASTM and EN standards. An enhancement of glycerol removal was found by adding small amounts of water up to the maximum solubility limit in biodiesel. An increase in temperature resulted in an increase in the solubility of water in the FAME and less effective glycerol removal. Application of cake filtration theory and a gel layer model showed that the gel layer on the membrane surface is not compressible and the specific cake resistance and gel layer concentration decrease with increasing temperature. An approximate value for the limiting (steady-state) flux was reported and it was found that the highest fluxes were obtained at the lowest initial water concentrations at fixed temperatures. In conclusion, dispersed glycerol can be successfully removed from raw FAME (untreated FAME) using a membrane separation system to meet the ASTM biodiesel fuel standards. The addition of water close to the solubility limit to the FAME mixture enables the formation of larger glycerol droplets and makes the separation of these droplets straightforward.

<p> An investigation has been made concerning the solubility of nitrogen in pure liquid iron, iron-carbon and ironaluminium alloys. A technique involving levitation melting and a rapid quench device has been used. The experimental data obtained have been expressed in terms of the interaction coefficients proposed by Wagner and Lupis and Elliott. The data have also been used to test the formalisms developed recently by Darken and Chipman. A simple model for liquid metal solutions in which the solutes may be considered "interstitial" has been developed and tested using the results of the present study and published data for a number of ternary solutions </p> / Thesis / Doctor of Philosophy (PhD)

Advanced drug delivery systems have shown immense success through nanotechnology which overcomes the challenges posed by large sized particles such as poor solubility, bioavailability, absorption, and target-specific delivery. This study focuses on nano sizing by application of microreactor technology and nanoparticles to obtain polymeric particulate with a selection of model drugs for inhalation drug delivery routes. The development of nanoparticles of two challenging compounds in terms of solubility and permeability, namely Ibuprofen (IBU) and Salmeterol (SAL), was conducted using a continuous, controlled, and scalable system offered by microfluidic reactor with the incorporation of anti-solvent approach. The research explores the potential of this technology to enhance absorption rate and hence bioavailability of IBU via oral route, and SAL via inhalation. IBU, an anti-inflammatory drug, is classified as BCS Class II drug with low solubility and high permeability. SAL is a selective long acting β2-agonist which is co-dispensed along with a short-acting β2-agonist for quick relief of acute bronchoconstriction due to its long onset of action. This lack of the ‘kick’ effect in SAL can be attributed to its relatively higher lipophilicity which causes a delay in the diffusion to the β2 receptors on the smooth muscles. It is therefore feasible to assume that increasing the dissolution and/or diffusion rate of SAL in the interstitial fluids would reduce the delay between administration and the onset of action of this drug which would be beneficial to patients. Process and formulation parameters were investigated to optimize the production and stability of nano particles of both drugs using Y shaped microfluidic reactors. IBU results show that the smaller the angle between the two inlets were the smaller the particle size achieved. Moreover, the particle size increased with increasing the concentration of IBU solution. The effect of the polymer mixture ratio (PVP/HPMC) on the initial particle size was not clear though. The smallest particle size (113 nm) was achieved using 10° Y shaped chip with IBU concentration of 1 mg/mL and a polymer mixture of 0.3% w/v PVP and 0.5% w/v HPMC. Using a polymer mixture of 0.5% w/v of each polymer though yielded a better PDI (140nm and PDI of 0.5). Same observations were noted when the syringe pumps were replaced with a non-pulsatile pressure pump. Particle size though dropped significantly to 33nm. Stability data showed that all systems were practically stable regardless of the process or formulation parameters. In addition, a considerable 2.5 fold increase in dissolution rate was observed in the first 20 minutes when compared to the raw material. The optimized parameters were applied to SAL to produce nanocrystals with best result (59 nm) were obtained using 50µg/mL Salmeterol with microfluidics inlet angle 10° with non-pulse syringe pump. The stabilizing mixture was PVP 0.8% w/v and Tween 80 at a concentration of 0.02%. This approach offered a basis for the generation of nano sized SAL particles with higher fine particle fraction and better deposition in NGI than currently marketed formulations, thus providing a more efficient drug dose delivery and lung deposition.

The threat of the ongoing climate crisis requires the complete reduction of carbon emissions in the next two to three decades. Carbon dioxide electrochemical reduction (CO₂ER) poses a promising pathway to be able to maintain our current energy infrastructures in a carbon neutral fashion, by allowing the production of fuels and chemicals, such as CO, methanol and ethylene, with the use of carbon capture technologies and green energy. Thus far, Cu is the only metal that has demonstrated the ability to form hydrocarbon products. However, Cu is hindered by low selectivity. Improvements have been observed by coupling Cu with noble metals, such as Ag and Au. However, despite significant advancements, the technology has yet to achieve sufficient performance in activity, stability and selectivity for commercial viability. As such, this work pursued to further advance the activity of CO₂ER through the use of plasmonic Cu-based catalysts and the study of novel dinitrile-based electrolytes. It has recently been identified that CO₂ER can benefit from direct plasmonic effects induced by light illumination. In essence, certain light wavelengths can induce collective oscillations of the free electrons in the metallic particles, leading to an enhancement of their electrocatalytic performance. As such, the first project of this work involved the development and testing of plasmonic Cu-Ag bimetallic catalysts for the application of CO₂ER. Cu, Ag, as well as Cu-Ag bimetallic particles with variable morphologies were able to be synthesized through a facile one-pot sodium borohydride chemical reduction method. The synthesized catalyst performance was also compared to commercial catalysts. The synthesized particles were found to be active catalysts for CO₂ER, with improved electro-catalytic activities exhibited by Cu₈₅Ag₁₅, Cu₆₀Ag₄₀ and Cu syntheses in respective order. All nanoparticles demonstrated increases in the catalytic activity ranging between 15-26% under white light illumination, attributed to plasmonic promotion. The best plasmonic promotion of 26% was observed in the CuAg commercial alloy. Meanwhile, the best promotion of the synthesized bimetallic particles was of 18% found in the Cu₆₀Ag₄₀ catalyst. Additionally, improved electrochemical and plasmonic stability was observed with the use of the Cu-Ag bimetallic synthesized structures compared to monometallic Cu. In addition, most studies pertaining CO₂ER involve aqueous electrolytes due to their low cost and low toxicity. However, these systems are hindered by mass transfer limitations due to the low solubility of CO₂ in water. Organic-based electrolytes have been subjects of research as they possess higher CO₂ solubilities to water. As dinitriles pose a novelty in the role of CO₂ER, dinitrile-based electrolytes were studied and tested for the application. It was hypothesized that due to the decreased polarity in dinitrile solvents, CO₂ concentrations in the electrolyte would increase leading to improved catalytic activity. The testing was conducted by evaluating and comparing acetonitrile (ACN), adiponitrile (ADN) and sebaconitrile (SBN) solvent-based electrolytes. Increased CO₂ solubility was observed in the dinitriles with 582 mM and 503 mM of dissolved CO₂ in ADN and SBN respectively, compared to 270 mM in ACN. Results were corroborated through DFT modelling, indicating preference of CO₂ absorbance to nitrile groups on the molecules. However, despite increases in CO₂ concentration, the electrochemical activity decreased from ACN > ADN > SBN. The trend in activity was observed to be inversely proportional to the viscosity of the dinitrile solvents, which affected the ionic conductivity. Based on these developments, the present thesis opens a new perspective for the use of Cu-based nanoparticles for direct plasmonic enhancement with the use of a broad-range wavelength white light. Furthermore, the work also sheds light on the properties and resulting electrocatalytic activities of the use of dinitrile organic electrolytes for CO₂ER. The presented findings provide significant groundwork for further developments in the realm of CO₂ER.

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