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    Removal of dissolved reactive phosphorus from municipal and dairy factory wastewater using allophanic soil : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Soil Science, Massey University, Palmerston North, New Zealand
    (Massey University, 2019) Cheuyglintase, Sasikunya
    Many of New Zealand’s sewage treatment plants (STPs) and rural factories discharge treated or partially treated sewage, which is rich in dissolved reactive phosphorus (DRP), into rivers and streams. A large number of these STPs are not able to comply with the current DRP river standards because conventional treatment methods are cost-prohibitive. There is an abundance of Allophanic soils with high phosphorus (P) sorption capacities located in the central North Island of New Zealand that have potential for use as low-cost filter material for removing DRP from wastewaters. For Allophanic soil filters to be a viable treatment option, the soil, in addition to having a high P sorption capacity, should be both accessible and plentiful. The main aims of this study were to assess and improve the effectiveness of Allophanic soil filters at removing DRP from wastewaters and to evaluate the agronomic value of P-enriched soils as a P source for plant growth. It also sought to contribute to a better understanding of the feasibility and important design characteristics of fullscale soil-based treatment systems. Five quarry sites in the Waikato Region were soil sampled to identify soils with high P retention values. Only the Te Mata Quarry (TQ) soil in the, northwestern Waikato Region, had a high P retention value at or close to 100% as assessed using the standard (5 g) anion storage capacity (ASC) test. The modified (1 g) ASC test revealed P retention values of 47 – 91% for samples taken from different soil depths at TQ. All of the soil depths down to 600 cm, except for the 125 – 175 cm depth, had modified (1 g) ASC test values >58%. This indicated that the TQ soil had P sorption capacities that would potentially make it a suitable material for filtering DRP from wastewater and, therefore, it warranted further evaluation using real wastewater. Wastewater pH has a marked influence on the P sorption capacity of soil filters, with the sorption capacity expected to increase as wastewater pH is decreased, from being alkaline to acidic. The laboratory soil column experiment quantified the effect of the level of acid dosing and the type of acid used on the capacity of soils to remove P from wastewater. Columns of soil, taken from a quarry at Ohakune (OQ), and treated with wastewater adjusted to pH 5.5 removed the greatest amount of DRP. A total of 8.9 mg P/g oven-dried soil was removed at an average removal efficiency of 75%. In comparison, the soil columns treated with wastewater without pH adjustment, removed only 4.5 mg P/g oven-dried soil at the same removal efficiency of 75%. This highlights the merits of lowering wastewater pH to increase DRP removal capacity. The performance pilot-scale soil filters at the Dannevirke STP and Fonterra Te Rapa WTP were evaluated, under field conditions, for a total operational period of 440 and 376 days, respectively. Each filter contained the OQ soil and had a surface area of 1 m². The OQ soil had an overall P removal efficiency of 67% and 71% at the STP and WTP sites, respectively. The OQ soil filters at Dannevirke STP removed a total of 6.4 mg P/g oven-dried soil, while the OQ soil filters at the Fonterra Te Rapa WTP removed a total of 1.87 mg P/g ovendried soil. This discrepancy in performance was due to the difference in wastewater type and pH adjustment, initial P concentrations, and soil pretreatment (i.e. the soil used at Dannevirke was sieved). A cost/benefit analysis suggested that if the STP was 225 km from the soil source then the cost of acid dosing is about ten times greater than the cost of supplying additional soil to achieve the same amount of P removal. Therefore, it is unlikely that acid dosing will be cost competitive for most wastewater treatment sites in the central North Island of New Zealand. The wastewater treated soil (WTS) obtained from the Dannevirke STP pilotscale filter experiment was evaluated for its agronomic effectiveness in a glasshouse pot experiment. The ability of WTS to supply P for ryegrass growth (Lolium multiflorum) was compared with a soluble phosphorus source (monocalcium phosphate, MCP). The WTS was highly effective at increasing available P in the soil, as measured by the Olsen P soil test, ryegrass yield and ryegrass P uptake. The soluble fertiliser P value of WTS was estimated to be equivalent to 61% of MCP applied at the same rate. Therefore, the results show that WTS is an effective P source for plant growth and its application to soil has the potential to recycle both the soil and the P it contains.
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    Design of bacterial polyester beads for recombinant protein production, biomolecule separation and detection : a thesis presented in partial fulfilment of the requirements of the degree of Doctor of Philosophy in Microbiology at Massey University, Palmerston North, New Zealand
    (Massey University, 2018) Du, Jinping
    Protein recovery and biomolecule detection are commonly required for scientific research as well as industrial activities. However, it is generally complicated and costly either to produce and purify recombinant proteins (especially therapeutic proteins) from engineered Escherichia coli cells, or to directly separate proteins or detect other biomolecules from natural sources. Here the PHA synthase (PhaC) mediated polyhydroxyalkanoate (PHA) bead display technology was explored as a solution to these problems by developing streamlined processes with less complex steps to achieve protein recovery and biomolecule detection. Firstly, by fusing a target protein to PhaC via a self-cleavable linker tag of either sortase (sortase A from Staphylococcus aureus) or intein (DnaB mini intein from Synechocystis sp. PCC 6803), new self-cleavable recombinant protein production and purification resins were developed. It was shown that the PhaC fusion could mediate in vivo production of PHA beads displaying the target protein. Functional target protein could be obtained at high purity from isolated PHA beads by incubation with CaCl2 and triglycine (in the case of the self-cleavable sortase tag) or by a pH shift to 6 (in the case of the self-cleavable intein tag). Six recombinant proteins were successfully produced and purified via the intein approach, including 3 model proteins (Aequorea victoria green fluorescent protein (GFP), Mycobacterium tuberculosis vaccine candidate Rv1626, and the synthetic immunoglobulin G (IgG) binding ZZ domain of protein A derived from Staphylococcus aureus) and 3 therapeutic proteins (human tumour necrosis factor alpha (TNFα), human interferon alpha-2b (IFNα2b), and human granulocyte colony-stimulating factor (G-CSF)). Of these, TNFα and IFNα2b were also successfully produced and purified via the sortase approach. Secondly, in vivo one-step production of PHA affinity resins was achieved by fusing to PhaC differently customised OBody ligands. These ligands were previously engineered by other groups from the OB-fold domain of aspartyl-tRNA synthetase (aspRS) from Pyrobactulum aerophilum, by using phage display technology, to have specific binding affinities to biomolecules of interest. The resulting recombinant OBody beads were used for lysozyme sepration from a complex substrate, and for progesterone (P4) binding. Further optimisation of the P4 binding condition is necessary before the OBody bead system can be used for P4 detection in bovine milk. However, recombinant immobilisation of OBody ligands on the surface of PHA beads expands not only the attractiveness of these emerging OBody scaffolds, but also the utility scope of PHA beads as affinity resins.
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    Understanding the mechanisms involved in Escherichia coli decay during wastewater treatment in High Rate Algal Ponds : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Environmental Engineering at Massey University, Palmerston North, New Zealand
    (Massey University, 2019) Chambonnière, Paul
    Little is known about the mechanisms and magnitude of pathogen disinfection in High Rate Algal Ponds (HRAPs). However, maturation ponds are used worldwide for wastewater disinfection, and pathogens can experience similar environmental conditions in maturation ponds and HRAPs. The literature suggests that pathogen removal in maturation ponds is primarily supported by sunlight-mediated mechanisms (direct DNA damage, endogenous photo-oxidation, and exogenous photo-oxidation), and a range of poorly characterized ―dark‖ mechanisms. Based on this evidence, and knowing HRAPs are specifically designed to optimize light supply into the broth, there is reason to believe sunlight mediated disinfection mechanisms should be significant in HRAPs. This thesis therefore aimed at identifying and quantifying the mechanisms responsible for Escherichia coli (E. coli) decay in HRAPs under the hypothesis that understanding the mechanisms involved in disinfection during wastewater treatment in HRAPs can provide the scientific foundation needed to optimize the design and operation for this critical wastewater treatment service. E. coli was selected for being an established indicator of the removal of faecal contamination during wastewater treatment. Two pilot scale HRAPs (0.88 m3) were commissioned and monitored over 1-2 years, showing a mean E. coli decay coefficient of 11.90 d-1 (std = 24.05 d-1, N = 128), equivalent to a mean E. coli log removal of 1.77 (std = 0.538, N = 128) when operated at a hydraulic retention time (HRT) of 10.3 d (std = 2.01 d, N = 139). Hourly monitoring showed high daily variations of E. coli log removal (up to 2.6 log10 amplitude) during the warmest summer days, with the lowest E. coli cell counts observed in the late afternoon, when the broth pH, dissolved oxygen concentration, and temperature typically reached peak values in the HRAP. No mechanisms driving E. coli removal in HRAP could be identified during the monitoring of pilot scale HRAPs so a mechanistic study of E. coli decay was performed at laboratory and bench scale to individually quantify potential mechanisms. At laboratory scale under various conditions (e.g. darkness vs sunlight exposure, neutral pH vs alkaline pH, RO water vs filtered HRAP broth), direct DNA damage, endogenous photo-oxidation, and high-pH toxicity were identified as the main mechanisms contributing to E. coli decay. Exposure to potentially toxic algal metabolites and exogenous photo-oxidation were not found to be significant under the conditions tested. Natural decay (i.e. decay in conditions identified not to be detrimental to E. coli survival) was never significant. The impact of predation could not be investigated due to technical challenges although pilot scale observations suggested this mechanism may be significant in certain conditions. Subsequent bench-scale tests conducted in HRAP broth indicated that temperature-dependent uncharacterized dark decay (i.e. decay in conditions not known to be detrimental to E. coli survival) was likely to be the dominant mechanism of E. coli removal under conditions relevant to full-scale operation. Temperature-dependent high-pH toxicity was confirmed to further increase E. coli decay at pH levels commonly reached in HRAPs. The contribution of sunlight mediated mechanisms was however not significant. Exposure to toxic algal metabolites was suspected to cause significant E. coli decay at times of extreme photosynthetic activity, but more research is needed to confirm this mechanism and its true significance. Results from laboratory scale and bench scale experiments enabled the development of a model capable of predicting E. coli decay in HRAP broth according to pH, temperature, and sunlight intensity distribution. A model predicting HRAP broth temperature and pH according to design and weather data was also developed and validated against data from the pilot scale HRAPs monitored during this study for temperature (average absolute error of predictions 1.35°C, N = 25,906) and pH (average absolute error of predictions 0.501 pH unit, N = 23,817). Coupling the E. coli decay model with the environmental model enabled long term predictions of E. coli removal performances in HRAP for various weather conditions, design, and operational regimes. Simulations predicted that a 3-HRAPs series would sustain average yearly E. coli log-removal of 3.1 in Palmerston North, New Zealand when operated in conditions similar to the pilot scale HRAPs used in the present study. Such performance would deliver year round compliance with local microbial quality guidelines. Disinfection performance could be further improved by increasing the hydraulic retention time, lowering the depth, or collecting the effluent once daily in the late afternoon while letting HRAP depth fluctuate. Overall, this research challenges the common belief that sunlight mediated disinfection mechanisms contribute the most to pathogen removal in HRAPs. Instead, uncharacterized dark decay was predicted to cause 87% of the total E. coli decay over one year simulation. High-pH toxicity may significantly contribute to overall E. coli decay in specific conditions (e.g. low depth where high-pH toxicity was predicted to account for 33% of total yearly E. coli decay), while sunlight mediated disinfection was limited under all simulated designs and operations (highest contribution predicted being 16% of total yearly E. coli decay). Because this study also confirmed the potential of HRAP to achieve sustained wastewater disinfection, further research is needed to better characterize dark decay mechanisms (for E. coli and other key indicators) as this knowledge has the potential to further improve HRAP design and operations for wastewater disinfection.
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    Elevating phosphorus accumulation in waste stabilisation pond algae : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Environmental Engineering at Massey University, Palmerston North, New Zealand
    (Massey University, 2019) Sells, Matthew
    Facultative waste stabilisation ponds (WSP) are used globally for wastewater treatment due to their low cost and simple operation. While WSPs can be effective at removing organic pollutants and pathogens, phosphorus removal is typically poor. Algae that are common in WSPs are known to accumulate phosphorus and increase their phosphorus content in the biomass from 1% up to 3.8% (gP/gSS), which is believed to be from the production of intracellular polyphosphate granules. This phenomenon, known as luxury uptake, may be possible to manipulate to improve phosphorus removal in WSPs; however, its occurrence is sporadic and poorly understood. This PhD thesis was undertaken to investigate the conditions that influence phosphorus accumulation in WSP algae. Phosphorus accumulation was quantified using two methods: (1) the traditional phosphorus content in the biomass (gP/gSS), and (2) a new image analysis method developed in this thesis that quantifies stained polyphosphate granules within individual algal cells (μm2 granule/μm2 cell). Following a literature review and screening experiments that sought to identify variables that could affect the phosphorus content in the biomass (gP/gSS), six variables: temperature, phosphorus concentration, light intensity, mixing intensity, organic load, and pH were comprehensively examined using 40 batch factorial experiments (26-1) and a mixed genus culture from a full-scale WSP. Nine variables and interactions had a significant effect on the phosphorus content in the biomass and were incorporated into a regression equation. This ‘mixed genus’ regression equation was tested against literature data, where seven out of the eight batch experiments from the literature were successfully predicted. In order to identify if the batch findings could be applied to a continuous process, which is more typical of full-scale WSPs, a bench-scale novel ‘luxury uptake’ process was designed, built, and operated under five different scenarios. The regression equation successfully predicted the experimental results for three of the five conditions examined. It was theorised that differences in behaviour at the genus level might explain why all five conditions were not successfully predicted. In an attempt to improve the prediction capability, the ‘black-box’ of mixed genus analysis was ‘opened’ to allow the effects of variables on phosphorus accumulation at the genus level to be directly examined. To achieve this, a new image analysis method was developed that quantified stained polyphosphate granules in individual algal cells. To ensure the granules being measured were indeed polyphosphate, algal cells were analysed using transmission electron microscopy coupled with energy dispersive X-ray spectroscopy, which confirmed the granules contained higher levels of phosphorus compared to the remaining cell. The image analysis method was then used to quantify stained polyphosphate granules in individual cells from the 40 batch factorial experiments mentioned previously. The results using the image analysis method showed that, for the five most abundant algal genera, Micractinium/Microcystis had the highest average accumulation of polyphosphate granules (17% μm2 granule/μm2 cell), followed by Scenedesmus (12%), Pediastrum (11%), Monoraphidium (8%), and Actinastrum (4%). Although none of the genera studied had the same combination of significant variables, all five genera preferred a high phosphorus concentration to elevate polyphosphate granule accumulation. Furthermore, a high light intensity, high organic load, or high temperature was preferred by the algae if the variable was significant for that genus. The culture used in the bench-scale continuous flow ‘luxury uptake’ process originated from a mixed genus WSP culture; however, it had become dominated by the Scenedesmus genus. Therefore, the regression equation was refined to use the batch data for this genus alone. This new Scenedesmus regression equation was compared against the experimental data from the ‘luxury uptake’ process previously mentioned. Polyphosphate granule accumulation was now successfully predicted in all five experimental conditions at the 95% confidence level. This improved prediction capability indicates that an understanding of the algal genus present in a WSP system is required for accurate predictions of the phosphorus accumulation to be obtained, and the batch data can indeed be applied to a continuous process. An unexpected result of the research was that, contrary to what was believed in the literature, an increase in the phosphorus content in the biomass did not necessarily increase the polyphosphate granule accumulation. Further examination identified that individual cells from the same algal species had varying polyphosphate granule contents from 0% to over 20% (μm2 granule/μm2 cell) when exposed to the same conditions. This variation was hypothesised to be from cellular functions influencing the granules differently depending on the individual alga’s cell cycle. In addition, when the phosphorus content in the biomass was increased above 2.1% (gP/gSS), no significant effect on the average quantity of polyphosphate granules was observed. This finding indicates that other forms of phosphorus storage must be responsible for attaining a highly elevated phosphorus content in the biomass.
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    The purification and steady state kinetic characterisation of rat liver mitochondrial malate dehydrogenase : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Biochemistry at Massey University
    (Massey University, 1988) McKay, Duncan
    Mitochondrial malate dehydrogenase (mMDH) is one of the enzymes in the malate-aspartate shuttle system which facilitates the movement of reducing equivalents across the mitochondrial membrane. The metabolism of ethanol in the cytosol of liver tissue requires large amounts of NAD+ and produces NADH, which must be oxidised back to NAD+ in the mitochondria. The transfer into the mitochondria is carried out by the shuttle system which may thereby contribute significantly to the control of ethanol metabolism under certain circumstances. In the shuttle system mMDH acts in the opposite direction to the cytosolic form of the enzyme. Is this due to differences in the functioning of the two isozymes or to differences in their environments? In this study a new method for the purification of mMDH from rat liver has been developed. This method was developed to be quick and to cause as little disruption to the protein structure of the enzyme as possible. The scheme involves the partial purification of mitochondria by centrifugation followed by elution, by NADH, off carboxymethyl cellulose chromatography resin. The whole process takes two days, because of the need to dialyse the sample to remove NADH, before any kinetic studies can be carried out. The specific activity of the purified enzyme compares favourably with other published values and the enzyme shows up as a single band on an SDS polyacrylamide electrophoresis gel. The major problem with the enzyme produced was its lack of stability during storage. The second part of the project was to carry out steady state kinetic experiments with the purified enzyme under conditions that simulate the in vivo state. These are 37°C, pH 7.4, and 0.1 M phosphate buffer. The dissociation and Michaelis constants, for other tissues, have been published before but not those for rat liver. Very few of these experiments have been carried out under these near physiological conditions. The kinetic parameters produced are (µM): Ka, 72; Kia, 12; Kb, 86; Kib, 18; Kp, 1900; Kip, 15000; Kq, 170; Kiq, 1100; where a = NADH, b = oxaloacetate, p = malate, and q = NAD+. Some of these values have extremely high standard errors and so need further refining. The values produced in this work can be compared to those for cytosolic malate dehydrogenase (Crow et al., 1982) and because the two sets of constants are quite similar it appears that the different modes of action in vivo are mostly due to differences in the environment of the two isozymes.
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    The purification and immunological isolation of ATP citrate lyase from rat liver : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Biochemistry at Massey University, New Zealand
    (Massey University, 1986) Walker, Brett Keith
    ATP CITRATE LYASE (E.C 4.1.3.8) has been purified from rat hepato­cyte cytoplasm by a combination of existing published procedures. The final purification method produced homogeneous ATPCL with specific activity of 10-16 units/mg. Antibodies were raised in rabbits against purified ATPCL eluted from reactive Blue Sepharose CL-68 or DEAE anion exchange column. The purified antibodies were tested for their specificity for ATPCL. This was accomplished by Ouchterlony double diffusion analysis and also by disruption of antibody-antigen complexes and visualizing the gene­ rated protein bands on detergent gels. The equivalence point of the purified antibody was determined by immunotitration with both purified enzyme and crude extract. The equi­valence point was later confirmed by immunotitration of radiolabelled proteins. Antibodies were then used to immunochemically isolate and quantitate the amount of (35-S) methionine or (14-C) radiolabelled ATPCL in the cytosolic fraction of rat liver. Pulse labelling of rat liver proteins in vivo and then precipitation of radiolabelled proteins demonstrated that the purified antibodies precipitated proteins other than just the ATPCL subunit. The amount of ATPCL present in the cytosolic fraction could be calculated after immu­ noprecipitation and excision of radiolabelled ATPCL subunition SOS-PAGE. The proportion of ATPCL protein to the total TCA precipitable protein could then be calculated since the immunoprecipitation was carried out under conditions of antibody excess. Radiolabelled ATPCL was then immunoprecipitated from the cytosolic fractions of rats that had been subjected to different nutritional regimes. The results of this set of experiments showed that induction of ATPCL activity resulted from an increase in immunologically reactive protein. Increasing amounts of radiolabelled immunoreactive ATPCL protein could be precipitated by antibodies as the enzyme was induced. Induction of ATPCL activity resulted from increased rate of synthesis or decreased rate of degradation of immunoreactive protein and not from the activation of pre-existing enzyme protein.
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    Site directed mutagenesis and purification of the cDNA for human class I aldehyde dehydrogenase : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science at Massey University
    (Massey University, 1998) Wansbrough, Erin M
    Aldehyde dehydrogenase (ALDH) is a key enzyme of alcohol metabolism, removing acetaldehyde which is formed as a product of the alcohol dehydrogenase reaction. If acetaldehyde is not effectively removed, acetaldehyde accumulates and produces an adverse reaction to alcohol, with nausea, flushing and increased heart rate and blood pressure. ALDH is involved in the conversion of retinal to retinoic acid (RA). RA has recently been shown to bind to receptors, which then act as nuclear transcription factors and play important roles in foetal development and maintenance of the epithelial layer in the body. Interference by ethanol and perhaps by acetaldehyde with this process is probably the cause of Foetal Alcohol Syndrome. In addition ALDH is also involved in the metabolism of catecholamine neurotransmitters, plays a role in the removal of toxic substances from the body and may have a role in protection against some chemical carcinogens. Dr. Kerrie Jones had obtained moderate levels of expression of recombinant ALDH in E. coli and constructed a number of mutants chosen on the basis of chemical modification data and sequence alignment. Mutant proteins were also expressed and assayed for enzyme activity in crude extracts. The aim of this thesis was to improve purification and yield of the expressed ALDH proteins. By the use of site-directed mutagenesis I attempted to mutate the amino acid residue Lys272 to either alanine, histidine or arginine. Future comparison of the properties of the site-directed mutants with those of the wild type enzyme will help to determine the importance of the residue (which has been replaced by mutagenesis) to catalysis.
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    Purification of TrkA intracellular domain and the characterization of novel intracellular proteins : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Molecular Biology at Massey University
    (Massey University, 1999) Walker, Scott David
    Nerve growth factor (NGF) binds to its receptor, TrkA, at the tips of nerve cell axons to inhibit apoptosis, causing survival and differentiation. Some factors within this process are largely unknown, such as the role of the p75 receptor and the molecular mechanisms that occur within the cell. NGF binding causes dimerization of TrkA, which activates the intracellular kinase domain. Autophosphorylation on tyrosine residues stimulates binding to the receptor of several intracellular proteins that mediate the NGF response. This receptor complex has been demonstrated to be retrogradely transported to the cell body. Retrograde transport is hypothesized to occur in small vesicles that have been isolated in our lab using a cell fractionation protocol using in vitro reactions with an ATP regenerating system. Discovering the initial molecular interactions that occur upon NGF binding could further our knowledge of NGF's inhibition of apoptosis, providing us with a possible tool for treatment of diseases that occur when the regulation of apoptosis no longer exists. Novel proteins that were not previously identified were associated with TrkA in small vesicles after NGF activation. To isolate these proteins for further characterization, TrkA's intracellular domain (TrkAID) was expressed in E. Coli. This protein was found to be constitutively tyrosine-phosphorylated and therefore presumably active. In E.Coli, TrkAID protein was localized to the soluble fraction but smaller amounts were detected in the insoluble fraction. TrkAID was partially purified from the soluble fraction using a combination of salt disruption and denaturing techniques. The unpurified TrkAID was immunoprecipitated from the bacterial soluble fraction with an antibody to the C-terminus of TrkA, and some results suggest that immunoprecipitated TrkAID was able to stimulate ERK activation in untreated PC12 cells, but unfortunately this was not reproducible. If the protein could be purified with a combination of techniques, then it would provide a useful tool for studying the initial events in NGF stimulation, that is, the recruitment of several intracellular proteins to the tyrosine-phosphorylated intracellular domain of TrkA.
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    Purification and kinetic characterisation of class 3 bovine corneal aldehyde dehydrogenase : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Chemistry at Massey University
    (Massey University, 1999) Woodhead, Brendon John
    Aldehydes can be found in a wide variety of places. For example, formaldehyde, acetaldehyde and acrolein are products of combustion and are present in smog and cigarette smoke (Schaucnstein et al., 1977). In addition, many foods, such as fruits and vegetables, are sources of aldehydes (Schauenstein et al., 1977). Aldehydes can also function as communication molecules, either between species or within a species, but the majority of aldehydes which are encountered are physiologically derived intermediates in the metabolism of other compounds (Schauenstein et al., 1977). Aldehydes can be generated from numerous endogenous and exogenous sources. Endogenous aldehydes include aldehydes arising from the metabolism of amino acids, biogenic amines, carbohydrates, vitamins, steroids (Schauenstein et al., 1977) and as a result of membrane lipid peroxidation (Esteibauer et al., 1990). Examples of some exogenous derived aldehydes include aldehydes resulting from the oxidation of primary alcohols (Williams, 1959) and from combustion (Schauensteinetal., 1977). In general aldehydes are biologically toxic due to the highly reactive nature of their electrophilic carbonyl group which can react with cellular nucleophiles, including proteins and nucleic acids. But not all aldehydes are biologically detrimental; for example, retinoic acid, the oxidation product of retinal, is involved in embryonic differentiation, and retinal itself is required for vision (Siegenthaler, et at., 1990). Some aldehydes may be chemotactic, that is they can recruit cells to sites of injury or inflammation (Dianzani, 1989).[FROM INTRODUCTION]
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    Model based study of autothermal thermophilic aerobic digestion (ATAD) processes : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Engineering and Automation of Massey University
    (Massey University, 2000) Fryer, Barry
    An Autothermal Thermophilic Aerobic Digestion process, or ATAD process, is a relatively new sewage sludge treatment process. The ATAD process has been developed for the disinfection and stabilisation of sewage sludge, which is a by-product of wastewater treatment. The end product can be applied to the land as a soil additive or fertiliser with no restrictions, as the process dramatically reduces public health and environmental risks. The process is comparable to the composting process used for municipal solid waste and garden wastes. The process requires oxygen, usually in the form of air, to be applied to the sludge by an aeration system. The oxygen stimulates an exothermic biochemical reaction, which in turn heats the sludge up to thermophilic temperatures (between 50 and 65°C). At these temperatures the pathogenic bacteria, viruses and parasites in the sludge that are harmful to human health are effectively destroyed. The biochemical reaction also degrades a large portion of the organic sludge, which means that unstable, volatile odour generating substances are removed; this reduces the likelihood of smells and the attraction of flies and rodents (vector attraction) to the sludge.[FROM INTRODUCTION]