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(2010)ThesisThis thesis evaluates the MicroFoss system, also known as the BioSys or the SolerisÒ system, as a rapid method for microbiological analyses of eggs and egg products. Commercially assays for assessment of microbiological quality and sanitation conditions during processing, which are total viable counts (TVC), coliforms and Escherichia coli, are evaluated in comparison to the cultural methods. Concurrently, this thesis reports development of a new medium for the MicroFoss Salmonella detection, since this test is not available. Good correlations between the cultural TVCs and the MicroFoss detection times (DTs) were obtained (r ³-0.84) in all egg products. Preliminary results of a correlation between the cultural TVCs dominated by Pseudomonas fluorescens and the MicroFoss DTs suggested that the MicroFoss could be used for investigation of spoilage and shelf life prediction of eggs. High agreements (r ³-0.93) between the MicroFoss and cultural methods for coliforms and E. coli in eggs and egg products was achieved as well as the accuracy, sensitivity and specificity. The MicroFoss for estimations of TVC, coliforms and E. coli could be completed in less than 24h, compared to 48-72h required for the cultural methods. Hence, the MicroFoss could be used as a rapid screening for quality control of eggs and egg products. While a new propylene glycol-based selective medium developed was effective for detection of Salmonella, possible false positive results caused by certain bacteria, such as Enterobacter cloacae, E. coli, Klebsiella pneumoniae and Proteus mirabilis, were encountered. When this selective medium was supplemented with 40 mg/L of novobiocin, or 1 or 2 mL/L of Niaproof 4, these non-salmonellae were greatly suppressed or eliminated, particularly Pr. mirabilis, whilst this did not affect growth of Salmonella. Various serotypes of Salmonella including strains of atypical biotype were able to acidify propylene glycol in these media. Detection of Salmonella in naturally contaminated eggs by the MicroFoss using propylene glycol-based selective media showed equivalent sensitivity and specificity to the Australian Standard 5013.10-2004, according to numbers of egg samples tested in this study. Detection of low level of Salmonella (1-10 CFU/25g of eggs pre-enriched in buffered peptone water) was achieved in less than 24h.
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(2010)Conference PaperAn opportunity to explore the topic of data usages is presented by the collaborative research being undertaken by a federation of applied science research units affiliated with a number of different Australian research organizations (the Cluster). The research aims to investigate how members of the collaboration understand and work with data in their day-to-day practice.
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(2010)ThesisThis work establishes a new approach 10 soft-sensor development for monitoring of variables for which there is no means of measurement. The study of unmeasurable variables is commonly performed with lengthy computer simulations, using methods such as the discrete element method (OEM) of modelling, which is used to simulate many particulate systems. In this thesis, rotating and stirred drums are simulated over a wide variety of operating conditions using DEM modelling, Microscopic scale data are obtained from the simulations and useful characteristics of particle interaction and motion determined for each operating condition. These characteristics are partide flow regime and impact intensity, which are very difficult or impossible 10 obtain experimentally. Particle-wall (p-w) impact event data are also collected from the simulations and processed to reflect the real collection of surface vibrations with accelerometers mounted on a drum shell. This data processing is informed by knowledge that the majority of surface vibrations measured by an accelerometer mounted on a drum shell are caused by p-w impact events adjacent to the accelerometer, and knowledge that these surface vibration signals can be decomposed to identify individual p-w impact events. Soft-sensors are then trained to predict partide flow regime and impact intensity using input variables extracted from p-w impact data. The soft-sensor structures are given by the multivariate methods of Fisher discriminant analysis (FDA) and principal component regression (peR), which are used for qualitative prediction of flow regime and quantitative prediction of impact intensity respectively. Using new input data the soft-sensors are found to satisfactorily predict the variables of interest, thus proving the concept of a soft-sensor that infers unmeasurable OEM data from surface vibration data. This work provides an approach to online monitoring of important process variables that are generally studied offline with lengthy DEM simulations.
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(2010)ThesisCharacteristics of irreversible protein residues on cleaned membranes are a crucial issue during membrane operations as the build-up of residues following repeated fouling and cleaning reduces membrane performance, purity and safety. In this study, the residual deposition of various proteins along a flat-sheet 30kDa Molecular Weight Cut-off (MWCO) polyethersulphone membrane was investigated. One Dimensional Sodium Dodecyl Sulphate ¬Polyacrylamide Gel Electrophoresis (10 SOS-PAGE) and Lowry method were utilized to determine cleaning effectiveness. Whey protein isolate, Bovine Serum Albumin (BSA) and Beta Lactoglobulin (BLg) solutions were used as foulants while Hydrochloric acid (HCI), Sodium Hydroxide (NaOH), and Protease M Amano enzyme were used as cleaners. The deposition was generally arbitrary due to the random nature of attachment and aggregation of the protein molecules. However these fluctuations can be reduced when a spacer was inserted in the channel resting above the membrane. When recovering the membrane flux, sequential cleaning with HCI and NaOH was more effective than NaOH cleaning alone. The inclusion of Hel was beneficial for severely fouled membranes with high amount of residues. The highest flux recovered through sequential cleaning for repeated fouling and cleaning cycles was 88%, white protease cleaning alone recovered 77%. Chemical cleaning leaves behind residues under the 20kOa molecular weight however these proteins were undistinguished due to the limitations of 10 SDS-PAGE. On the other hand, protease cleaning leaves behind a distinct 3akOa protease residue on the surface. The cross-flow ultrafiltration of BSA solutions at various conditions was studied using empirical mass transfer models and Computational Fluid Dynamics (CFO) simulations. The CFO simulates the steady state flux and wall concentrations based on varying physical properties. The mass transfer study estimates individual resistances, mass transfer coefficients. and diffusivities through various models. The CFO shows good agreement between simulated and experimental fluxes over time however the simulation response to the varied conditions was only qualitatively similar. The effect of concentration polarization towards flux decline was high however it was underestimated in the CFO. While theoretical wall concentrations varied with pH, measured depositions were constant. The estimated diffusivities between CFD and mass transfer study concurred.
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(2010)ThesisThe aim of the present study was to develop a specific and quantitative assay to determine the individual concentrations of naturally occurring phenolic acids and their metabolites in food; then evaluate the antioxidant capacity of the quantified phenolic acids using different assays. A GC/MS method was developed for the quantification of ten commonly present phenolic acids in plant foods. Target analytes were the benzoic acid based phenolic acids - anisic, gallic, p-hydroxy benzoic, o-salicylic, protocatechuic, and vanillic acids, together with the cinnamic acid based phenolic acids - caffeic, p-coumaric, ferulic and sinapinic acids. Deuterated Anisic D7 acid was used as an internal standard to achieve accurate and reliable quantification. Purification was accomplished using C18 solid phase extraction cartridges (ENVI Chrome P, Supelco); sample extracts were derivatized prior to GC-MS analysis using BSTFA and pyridine (4:1 V/V). Resolution and quantification of all compounds were excellent with linear calibration curves over a wide range (0-500 ng/ml) and correlation coefficient (R2) of 0.999. Relative standard deviation (RSD) and response factors (RF) were satisfactory (≥1.1 and >3 respectively) and within the acceptable limits of bioanalytical method validation. The adapted method was applied to different varieties of fresh and sundried Saudi Arabian dates as well as Achacha fruit and eleven selected spices. The results revealed that phenolic acids are present in plant foods mostly in bound form as esters or glycosides. The lipophilic and hydrophilic antioxidant activities of all selected samples were examined using the ORAC assay. In addition, the antioxidant capacity of the identified free and bound phenolic acids was measured by different assays including ORAC, ABTS, DPPH and FCR. The results indicate that hydrophilic antioxidants are higher than lipophilic antioxidants in plant foods and the high phenolic acids content was not correlated with high antioxidant activity. Moreover different antioxidant capacity assays showed different results on the same phenolic acid extracts from different samples (P-value> 0.05). In conclusion the method presented is robust, safe, sensitive and generally applicable to the analysis of free and bound phenolic acids in food samples. The data obtained is sufficiently reliable to be included in food composition databases.
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(2010)ThesisEndocrine disrupting chemicals (EDCs) are chemicals that alter functions of the endocrine system and cause health effects in an intact organism, or progeny, or population, with reproductive, developmental, or carcinogenic consequences. In order to facilitate risk assessment of potential endocrine disrupting steroids that are present in ultra low concentrations in the Australian environment, there is a need to boost the analytical capacity for EDC detection. One strategy is to develop antibody-based techniques that can offer simple, cost-effective and reliable analysis with high throughput capacity and portability for real-time monitoring. This thesis describes the design and synthesis of hapten molecules, raising of specific antibodies, formatting and characterising of a series of sensitive competitive Enzyme-Linked Immunosorbent Assays (ELISAs) for 17β-estradiol (E2), 17α-ethynylestradiol (EE2), ethylestradiol-3-methyl ether (mestranol) and testosterone (T), including validation of their performance as fast and effective water monitoring tools. Application of the developed assays to investigate the levels of the target EDCs in bodies of water and efficiency of water treatment plants in urban and rural areas in New South Wales, Australia, is also discussed. 17α-Ethynylestradiol and related synthetic estrogens, are active ingredients of contraceptive pills and hormone therapy, and have been identified as potent EDCs (Warner and Jenkins, 2007). In Chapter 3, the development of two ELISAs with varying specificity for the synthetic estrogens is described; 1) a highly sensitive ELISA for 17α-ethynylestradiol and mestranol, and 2) a mestranol specific ELISA. Highly specific antibodies was facilitated by synthesising haptens with the attachment of linkers with varying lengths at the C3 position (17α-ethynylestradiol-acetate hapten (EE2-ACT-KLH) and 17α-ethynylestradiol-butyrate hapten (EE2-BUT-KLH)). The optimised ELISAs in heterologous systems displayed high sensitivity, with the best assay exhibiting a limit of detection (LOD) of 70 ng L-1 EE2 in water (without preconcentration). The LOD of the ELISA covering the preconcentration step was 0.13 ng L-1 EE2 in water samples. This ELISA also correlated well with GC-MS (R2 = 0.934) data that were conducted independently for the same spiked samples. In Chapter 4, the development and validation of competitive direct ELISAs (cd ELISA) for the detection of 17β-estradiol (E2) in water at sub-parts per trillion levels is described. The specific polyclonal antibodies were raised against KLH conjugates of 17β-estradiol-acetate hapten (E2-ACT-KLH) and 17β-estradiol-butyrate hapten (E2-BUT-KLH), using a similar hapten synthesis approach as for 17α-ethynylestradiol. The developed ELISA (denoted as E2 ELISA) was highly specific to 17β-estradiol with a LOD of 50 ngL-1 in water (without preconcentration), with high matrix tolerance. The LOD of the E2 ELISA covering the preconcentration step was 0.03 ngL-1in water samples. Validation of ELISA performance against an independently performed GC-MS method indicated good correlation with a R2 value of 0.936. In Chapter 5, the development of an ELISA specific for testosterone with respect to the desired sensitivity and specificity for environmental analysis is described. The ELISA presented with a LOD and IC50 value at 0.07 ng L-1 and 0.4 ng L-1, respectively, and an excellent specificity. Unlike previously described assays for the estrogens, this assay was more matrix sensitive. Hence, an alternative or enhanced sample preparation step prior to assay was deemed essential to improve assay performance. Finally, in Chapter 6, the application of these developed ELISAs for the investigation of the quality of influent and effluents from various Sewage Treatment Plants (STPs) and nearby water resources in New South Wales, Australia, is described. The estrogenic and androgenic activities of the respective water samples were 0.20 to 6.28 ng L-1 estradiol equivalents and 0.01 to 0.64 ngL-1 testosterone equivalents, respectively, as measured by the yeast screening assays. Regular monitoring of EDCs should be conducted to ensure the levels and the contribution of estrogenic potency in water bodies is maintained below the ecotoxicologically significant level of 10 ngL-1 (Fenske et al., 2005, Huschek and Hansen, 2005). In addition, agricultural practices including live stock husbandry should be controlled to a certain distance away from water sources as a precautionary measure to reduce estrogenic potency in our water resources. In conclusion, a satisfactory agreement in data for E2, EE2 and T was obtained between ELISAs, GC-MS, and the estrogenic/androgenic activities measured by the yeast screening assays, although a slightly higher estimation was observed by ELISA. This suggests that ELISAs developed in this project can be used as fast and cost effective water quality monitoring tools. The high sensitivity and specificity of these ELISAs allow them to be used to monitor with acceptable reliability of the estrogenic and androgenic steroids at low parts per trillion levels after a simple concentration step.
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(2010)ThesisMagnetic nanoparticles (MNPs) have attracted widespread interest in analytical chemistry because of their unique physical properties and the ability to manipulate MNPs with a magnetic field. These properties have led to a proliferation of research into the use of MNPs in a wide-range of analytical and sensing applications. Presented in this thesis is a study into the synthesis and modification of magnetic iron oxide nanoparticles (MIONs) with the ultimate aim being their application towards enhanced chemical sensing systems. The first section of the thesis reports the aqueous-phase synthesis of MIONs and a detailed study into the controlled adsorption of polyethyleneimine (PEI) onto the MIONs. The combination of MIONs with a PEI coating allows for the selective magnetic sequestration and quantification of ultra-trace levels of free cupric ions. The importance of controlled PEI adsorption for tailoring colloidal properties, as well as ensuring maximal cupric removal capacity is demonstrated. The second section of the thesis focuses on the modification of PEI-coated MIONs with gold to enable their use in electro-analytical applications. Reported in this section is a new method that was developed for the aqueous synthesis of 50-150 nm gold-coated MIONs, with the ability to engineer the coverage of gold coating. In-depth characterisation of the gold-shell formation process was performed. This section is concluded with a study into the functionalisation of gold-coated MIONs using thiol molecules with different functional groups for use as linkers in the attachment of functional molecules. The third section of the thesis explores the concept of utilising gold-coated MIONs as active elements in the selective capture and direct electro-analytical quantification of analytes. This system of ‘dispersible electrodes’ combines the ability to magnetically manipulate the dispersible electrodes, with enhanced electrical conductivity due to the gold coating. The ability of the system to reduce response times and improve detection limits of electrochemical sensors by bringing the sensor to the analyte rather than the conventional paradigm of bringing the analyte to the sensor is demonstrated.
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(2010)ThesisVetiver grass (VG) can be used for soil phytoremediation of various pollutants. The plant is of high tolerance for extreme climatic variations and hostile soil conditions and can produce high biomass. Vetiver can accumulate high concentrations of heavy metals as well as absorb and promote biodegradation of organic wastes. Essential oil extracted from roots of VG has aromatic and biological properties employed in several applications. VG oil and its fractions are extensively used for blending in oriental types of perfumes, cosmetics, foods and aromatherapy, and have applicable potential as pharmaceutics, insecticides and herbicides. The effect of Pb, Zn and Cu on vetiver oil yield and chemical composition was investigated. Oil content and yield are not affected at low and moderate concentrations of Cu and Zn. However, Pb has a significant detrimental effect on plant growth, oil yield and composition. Vetiver oils extracted by hydrodistillation were free of heavy metals. Results show that phytoremediation of Cu and Zn contaminated soils by vetiver can generate revenue from the production of oil extracts. To improve growth, oil yield and quality of VG grown on lead contaminated soils, the addition of CaCO3 was investigated. Calcium treatment increased vetiver growth and survival, but did not improve vetiver oil yield and chemical composition. A response surface method was applied to optimize the extraction yields produced by supercritical CO2 extraction (SCE). Operation at optimal conditions (190 bar, 50ºC and 100 minutes) produced vetiver oil yield about four times higher than that of hydrodistilation. Extraction pressure has a major linear effect on oil yield, whilst temperature and time have a lesser impact. The addition of ethanol increased extraction efficiency of SCE. At optimal conditions of 190 bar, 50ºC and 15 vol% ethanol, ethanol-modified-SCE produced a yield nearly double that of SCE without modifier operated at 190 bar and 50ºC. The operation at 100 bar, 40ºC and 15 vol% ethanol had nearly the same yield as that of optimal conditions. This finding allows extraction operated at low pressure and temperature. Metals accumulated in vetiver roots were not co-extracted with essential oils by either ethanol-modified SCE or SCE without modifier.
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(2010)ThesisThe thesis reports the synthesis of glyco-materials by utilizing controlled/living free radical polymerization. The latter is a powerful synthetic tool for building complex polymer architectures. Various glycomonomers namely, 1,2:3,4-Di-O-isopropylidene-6-O-acryloyl-alpha-D-galactopyranose (AIpGP), 2-(2 ,3 ,4 ,6 -tetra-O-acetyl-beta-D-galactosyloxy)ethyl methacrylate (AcGalEMA) and 2-methacrylamido glucopyranose (MAG) were initially synthesized via different chemical pathways and this is followed by employing reversible addition-fragmentation chain transfer (RAFT) polymerization and nitroxide-mediated radical polymerization (NMP) to achieve the desired amphiphilic diblock glycopolymers. To obtain carbohydrate functionalized materials, the amphiphilic glycopolymers were either self-assembled into stable micelles or simply synthesized in a one pot ab initio emulsion polymerization via RAFT to achieve glyco-latex particles. The bioactivity of the glyco-materials was examined by their specific multivalent interactions with lectins.
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(2010)ThesisProcess operability is fundamentally determined by the design of the process. An easy to operate process can achieve a good control performance even by using a very simple controller. On the other hand, regardless how good the control system is, when applied to a poorly designed process, it may not deliver the desired control performance. Operability analysis determines whether a process can be controlled effectively using a feedback control system. Such analysis is very useful in revealing potential operability problems in the early stages of process design. A vast amount of operability analysis methods have been developed based on open-loop models. These methods can be used without the need to design the control system for closed-loop simulations, hence remove the arbitrariness and lengthiness of the simulation based approach commonly applied in industry. However, most of the open-loop operability analysis methods can only be used for stable linear processes with specific control structures and pairings. Only a few methods are available for unstable linear processes and nonlinear processes. In this thesis, we develop a systematic approach to operability analysis of linear and nonlinear processes based on the concept of passive systems. Passive systems represent a class of minimum phase systems with relative degree no larger than one. This implies strictly passive systems are very easy to control. They can be controlled by any passive controller with any infinitely large positive gain. This also implies that the degree of passivity of a system can be used to indicate its operability. Moreover, the passivity theory is applicable not only for linear processes but also for nonlinear processes. This makes the passivity based method an excellent candidate for operability analysis of chemical processes. A chemical process in general consists of more than one unit operation. To assess the operability of multi-unit linear processes under various control structures and pairings, we develop a simple dynamic operability analysis method by extending the passivity based DIC and BDIC conditions to higher frequencies. Furthermore, since the operability of unstable processes is often a bigger concern in control practice, we also develop a dynamic operability analysis method that can be used for both stable and unstable linear processes based on coprime factorization and feedforward passivation. Operability analysis for nonlinear processes is often perceived as a very complex and computational demanding exercise by practitioners. To bridge the gap between existing passivity based operability analysis methods and their implementations, we develop a numerical framework for assessing the steady-state and dynamic operability of a nonlinear process solely based on the input-output data obtained from a process simulator. As such, it can be implemented conveniently as one extra step after the flowsheet simulation. Unlike linear processes, the passivity of nonlinear processes is usually defined with respect to one particular operating point of interest. To address the operability at various operating points, we also develop a dynamic operability analysis method for nonlinear processes based on incremental passivity. Throughout this thesis, we demonstrate how the passivity based analysis can be used across several process characteristics and requirements of practical interest.