Made available in DSpace on 2014-08-20T14:37:49Z (GMT). No. of bitstreams: 1 dissertacao_paula_finger.pdf: 729110 bytes, checksum: fe15bb22f0abb92bf1b2938fd6dcdfc9 (MD5) Previous issue date: 2011-12-19 / The chickens infectious bronchitis (IB) is a highly contagious viral disease which causes predominantly respiratory lesions manifested clinically and invariably by sneezing and tracheo-bronchial rales, which may lead to more severe signs, with a decrease in fertility and reduction of eggs production. The infectious bronchitis virus (IBV) encodes four major structural proteins: N (nucleocapsid protein), S (spike protein), E (envelope protein) and M (membrane protein) being the S protein is cleaved into S1 and S2. The 1 subunit (S1) is found exposed in the viral envelope, which makes it an important or main inducer of neutralizing antibodies against the IBV, the main target for the host s immune system. The variations in two regions of the envelope s S1 subunit, called hypervariables regions, may originate to new serotypes. The IBV s mutation and recombination capacity and the selection pressure exerted by the prolonged use of live vaccines contribute to the appearance of a wide variety of serotypes and subtypes of IBV. The objective of this study was to express, in Pichia pastoris, the gene that encodes the surface protein S1 of IBV strain M41 and, in Escherichia coli, to express the S1 of the synthetic gene designed from consensus sequences of national and international field samples, as an interesting alternative for the production of antigen that can be used for monitoring vaccination of birds and also an antigen that is suitable for the use in serological diagnostic. The cloning and expression of glycoprotein S1 in both heterologous expression systems was successfully performed. The process of expression using E. coli was simple and quick when compared to the use of P. pastoris. The P. pastoris was able to express the entire S1; however, it showed difficulty in secreting the glycoprotein. The results will be evaluated for use in immunodiagnostic kit for monitoring the disease in poultry, being more affordable than the ones existing currently. / A bronquite infecciosa das galinhas (IB) é uma enfermidade viral altamente contagiosa que causa predominantemente lesões respiratórias que se manifestam clinicamente e invariavelmente por espirros e estertores tráqueo-bronquiolares, podendo levar a sinais mais severos, com diminuição na fertilidade e redução da produção de ovos. O vírus da bronquite infecciosa das galinhas (IBV) codifica quatro proteínas estruturais importantes: N (proteína do nucleocapsídeo), S (proteína de superfície), E (proteína do envelope) e M (proteína da membrana), sendo a proteína S subdividida em S1 e S2. A subunidade 1 (S1) encontra-se exposta no envelope viral, o que torna-a um importante, ou principal, indutor da produção de anticorpos neutralizantes frente ao IBV, sendo o principal alvo para o sistema imune do hospedeiro. As variações em duas regiões da subunidade S1 do envelope, chamadas regiões hipervariáveis, podem dar origem a novos sorotipos. A capacidade de mutação e recombinação de IBV e a pressão de seleção exercida pelo uso prolongado de vacinas vivas contribuem para o aparecimento de uma grande variedade de sorotipos e subtipos de IBV. O objetivo deste trabalho foi expressar em Pichia pastoris o gene que codifica a proteína de superfície S1 da estirpe M41 do IBV e, em Escherichia coli, expressar a S1 de um gene sintético elaborado a partir de sequências consenso de amostras de campo nacionais e internacionais, como uma alternativa interessante para a produção de antígeno que possa ser utilizado para monitoramento vacinal das aves e também um antígeno que seja adequado para utilização em diagnóstico sorológico. A clonagem e a expressão da glicoproteína S1 em ambos os sistemas heterólogos de expressão foi realizada com sucesso. O processo de expressão usando E. coli foi rápido e simples quando comparado ao uso da P. pastoris. A P. pastoris foi capaz de expressar a S1 inteira, porém, apresentou dificuldade em secretar a glicoproteína. Os resultados obtidos deverão ser avaliados para uso em Kit de imunodiagnóstico para monitoramento da enfermidade na avicultura, sendo de custo mais acessível do que os existentes no mercado.

Benzaldehyde (BZA), a biologically derived high-value molecule used in the flavour and fragrance industry for its characteristic almond-like aroma, has also found use in nutraceutical, pharmaceutical, cosmetics, agrochemical, and dye applications. Although, nature-identical BZA is most commonly produced by chemical synthesis, biologically derived BZA, whether by plant material extraction or via microbial biocatalysts, commands much higher prices. The bioproduction of high value molecules has often been characterized by low titers as results of substrate and product inhibition. The current work examined a variety of process strategies and the implementation of a solid-liquid bioreactor partitioning system with continuous integrated pervaporation to enhance the bioproduction of BZA using Pichia pastoris. Previous work on two-phase partitioning bioreactors (TPPBs) for the biotransformation of BZA using Pichia pastoris has had limitations due to long fermentation times and unutilized substrate in the immiscible polymer phase, contributing to complications for product purification. To reduce fermentation times, a mixed methanol/glycerol feeding strategy was employed and reduced the time required for high-density fermentation by 3.5 fold over previous studies. Additionally, because BZA and not the substrate benzyl alcohol (BA) had been found to be significantly inhibitory to the biotransformation reaction, a polymer selection strategy based on the ratio of partition coefficients (PCs) for the two target molecules was implemented. Using the polymer Kraton D1102K, with a PC ratio of 14.9 (BZA:BA), generated a 3.4 fold increase in BZA produced (14.4 g vs. 4.2 g) relative to single phase operation at more than double the volumetric productivity (97 mg L-1 h-1 vs. 41 mg L-1 h-1). This work also confirmed that the solute(s) of interest were taken up by polymers via absorption, not adsorption. BZA and BA cell growth inhibition experiments showed that these compounds are toxic to cells and it was their accumulation rather than low enzyme levels or energy (ATP) depletion that caused a reduction in the biotransformation rate. For this reason, the final strategy employed to enhance the bioproduction of benzaldehyde involved in situ product removal by pervaporation using polymer (Hytrel 3078) fabricated into tubing by DuPont, Canada. This aspect was initiated by first characterizing the custom-fabricated tubing in terms BZA and BA fluxes. The tubing was then integrated into an in situ pervaporation biotransformation and was shown to be effective at continuous product separation, using 87.4% less polymer by mass in comparison to polymer beads in conventional TPPB operation, and improved overall volumetric productivity by 214% (245.9 mg L-1 h-1 vs. 115.0 mg L-1 h-1) over previous work producing BZA. / Thesis (Master, Chemical Engineering) -- Queen's University, 2013-09-28 17:41:45.458

La chymosine, enzyme utilisée dans l´industrie fromagère pour coaguler le lait, est traditionnellement extraite à partir du quatrième estomac de veaux non sevrés. La préparation ainsi obtenue dénommée présure a été depuis un certain nombre d´années substituée par divers coagulants d´origine microbienne et de plantes car la production de cette enzyme seule n´était plus capable de répondre à la demande mondiale du fait notamment de l´augmentation de la production fromagère. La chymosine est cependant toujours considérée comme étant la meilleure enzyme pour coaguler le lait dans l´industrie fromagère. Ainsi, les techniques d´ingénierie génétique ont été utilisées pour produire de la chymosine bovine recombinante. C´est en utilisant ces techniques que nous proposons d´établir un procédé de production de chymosine bovine recombinante permettant l'innovation technologique et contribuant au maintien et au développement d'entreprises agro-alimentaires brésiliennes et des pays du Marché Economique du « Cone Sul » (MercoSul).<br />Nous avons ainsi cloné les séquences codant la préprochymosine A et la préprochymosine B à l'aide des techniques classiques de biologie moléculaire. Nous avons observé la présence de mutations dans la partie du propeptide de la prochymosine A et dans la partie mature de la prochymosine B. Cette dernière mutation, S79N, se situe dans la partie du tampon (résidus 72 à 86) qui constitue une anse externe mobile recouvrant le sillon du site actif. La conformation de ce tampon est caractéristique de la chymosine et serait en partie responsable pour sa grande spécificité. Nous avons modélisé cette mutation, qui semble entraîner des changements dans le réseau de liaisons hydrogène du tampon. Les séquences obtenues ont ainsi été introduites dans différents vecteurs d´expression puis clonées chez Escherichia coli et Pichia pastoris. L'expression des protéines a été suivie à l'aide d'anticorps spécifiques et au moyen de tests d'activité. Les différentes protéines sont toutes actives et ont été purifiées à l'homogénéité. Nous avons alors étudié leurs propriétés cinétiques à l'aide de différents substrats. Les chymosines B et BS79N ont un optimum de pH qui les différencie de la chymosine A. Le mutant B S79N a des propriétés cinétiques améliorées avec l´hexapeptide synthétique. La mutation S79N n´entraîne toutefois qu´une petite augmentation de la constante d´efficacité concernant les hydrolyses de la caséine Κ et du lait, bien que ses vitesses de réactions catalytiques soient supérieures à celles de la chymosine B. Ces résultats sont expliqués par les modifications dans le réseau de liaisons hydrogène du tampon, et par le fait que le nombre d'interactions entre le substrat et l'enzyme est une fonction de la masse moléculaire et de la nature du substrat.

In this study, it was aimed to develop a bioprocess using the Pichia pastoris expression system as an alternative to the mammalian system used in industry, for production of the therapeutically important glycoprotein, erythropoietin, and to form stoichiometric and kinetic models. Firstly, the human EPO gene, fused with a polyhistidine-tag and factor-Xa protease target site, in which cleavage produces the native termini of EPO, was integrated to AOX1 locus of P. pastoris. The Mut+ strain having the highest rHuEPO production capacity was selected. The glycosylation profile of rHuEPO was characterized by MALDI-ToF MS and Western blotting. The native polypeptide form of human EPO was obtained for the first time in P. pastoris expression system, after affinity-purification, deglycosylation and factor-Xa protease digestion. Thereafter, effects of medium components and pH on rHuEPO production and cell growth were investigated in laboratory-scale bioreactors. Sorbitol was shown to increase production efficiency when added as a co-substrate. Moreover, a cheap alternative nutrient, the byproduct of biodiesel industry, crude-glycerol, was suggested for the first time for P. pastoris fermentations. Furthermore, methanol feeding strategy was investigated in fed-batch pilot-scale bioreactors, producing 70 g L-1 biomass and 130 mg L-1 rHuEPO at t=24h. Moreover, metabolic flux analysis by using the stoichiometric model formed, which consisted of m=102 metabolites and n=141 reactions, proved useful in further understanding the P. pastoris metabolism. Finally, the first structured kinetic model formed for r-protein production with P. pastoris successfully predicted cell growth, substrate consumption and r-product production rates, where rHuEPO production kinetics was associated with AOX production and proteolytic degradation.

In this study, effects of different carbon sources and their feeding strategies on recombinant human growth hormone (rhGH) production by Pichia pastoris were investigated by means of cell growth, recombinant protein production and expression levels of hGH and alcohol oxidase (AOX) genes. In this content, firstly, the strain to be used for high level rhGH production was selected between the two phenotypes, i.e., P. pastoris hGH-Mut+ and P. pastoris hGH-MutS. In this selection both phenotypes were compared in two different media containing glycerol/methanol or sorbitol/methanol and P. pastoris-hGH-Mut+ strain grown on medium containing 30 g/L sorbitol with 1% (v/v) methanol was found to have the highest hGH expression level and rhGH production level, 9.84x109 copies/mg CDW and 120 mg/L, respectively. Thereafter, effects of sorbitol, mannitol, fructose, lactose, sucrose, citric acid, lactic acid and acetic acid were investigated by using P. pastoris hGH-Mut+ strain in laboratory scale bioreactors. Among them sorbitol and sucrose were selected to be compared for production in pilot scale bioreactors by adding them batch-wise at the beginning of induction phase with fed batch methanol feeding scheme at &amp / #956 / =0.03h-1. It was shown that sucrose does not support cell growth as sorbitol although it does not repress recombinant protein production. Then three different feeding strategies were applied to develop sorbitol/methanol mixed feeding i) single sorbitol addition at t=0, ii) besides at t=0, adding second batch-wise sorbitol at t=9 h, iii) giving pulse methanol at t=24 h to trigger AOX promoter. These three strategies were compared with a production without addition of co-substrate sorbitol. Substrate consumption, cell growth, recombinant protein production and expression levels of hGH and AOX were investigated for these different feeding strategies. The highest cell concentration was achieved in third strategy as 55 g/L where the highest extracellular rhGH production (301 mg/L) was achieved in the second strategy, with addition of two times of sorbitol. For this highest recombinant protein production case, overall cell and product yield on total substrate were found as 0.17 g/g and 1.71 mg/g, respectively. Moreover, the highest hGH and AOX expression levels were obtained in this strategy.

Recombinant Pichia pastoris is one of the important methylotropic yeast due to its robustness and ability to produce hormones like human chorionic gonadotropin (hCG), luteinizing hormone (LH) extracellularly. High growth on glycerol and strong protein expression on methanol by insertion of alcohol oxidase (AOX) promoter demand the fermentation to be a multistage operation. Methylotropic pathway demands more oxygen as methanol has to be converted to formaldehyde with half mole of oxygen. Moreover as fermentation progresses cell density in the reactor also increases. In case of Pichia pastoris fermentation cell density usually reaches very high (above 100 gm/lit) at the end of fermentation. Both these contribute in the increased oxygen demand in the fermentation and oxygen transfer turns out to be a limiting step. The present study focuses on the oxygen transfer process and its improvement in the fermentation. Oxygen transfer in bioreactor is a multistep process and involves different kinetic as well as mass transfer steps. In case of fermentation especially at high cell densities, oxygen transfer from bubbles to the broth becomes limiting step. The interface transport is governed by many physical as well as kinetic parameters. It is essential to screen these parameters from the whole set to identify the key parameters. Sensitivity analysis is carried out by using Metabolic Control Analysis (MCA) to quantify the effects of different parameters. It is found that bubble size and oxygen partial pressure are two such key parameters which can be manipulated. Use of pure oxygen to increase partial pressure and thereby solubility of oxygen in broth is a common approach. This work focuses on bubble size manipulation to increase the oxygen transfer rates.The idea behind this work is on to generate micron sized bubbles and utilize them effectively in the fermentation. There are many techniques reported to generate microbubble dispersions. In this work ’Spinning Disc microbubble Generator’ is fabricated to generate microbubbles. A flat disc surrounded by baffles with 5 mm gap in between, when subjected to 5000 rpm generates microbubbles. Some modifications are done to the set up to achieve desired properties of the bubbles. The bubbles generated fall in the range of 30-300 micron with mean size of about 60 micron. Use of Tween-20 surfactant stabilize the bubbles and hence offer a good resistance to coalescence and breakage. The liquid fraction in the bubbles can be as high as 40%. Contineous addition of this dispersion unnecessarily can dilute the fermentation broth. To overcome this volume constrain, a recirculation system is designed. Microbubble dispersion is added contineously to the reactor and equivalent fermentation broth is pumped back to the microbubble generator to achieve steady state to the liquid volume in both the vessels. Mass transfer studies with microbubbles show the potential of microbubble dispersion (MBD) to enhance mass transfer significantly. Decrease in volumetric mass transfer coefficient (KLa) due to surfactant is overcompensated by the increase in the interfacial area and net effect is, potential enhancement in KLa. The enhance- ment factor, that is, ratio of mass transfer coefficient with MBD to mass transfer coefficient with conventional sparging, is obtained to be about 4 to 5. Prior to utilization of bubbles in the recirculation system, cells are checked for the shear sensitiveness. Negligible lysis losses and almost no effect on growth patterns in shake flask culture confirm that the cells used are mechanically stable at operating conditions. Better growth patterns in shake flask are observed when microbubbles are pumped for predetermined duration in the broth. It shows possible use of MBD as oxygen carriers. Glycerol batch phase with MBD and conventional sparging is studied at different initial cell densities. Conventional sparging fails to grow the cells and Dissolved Oxygen (DO) levels close to zero suggest high oxygen demands which can not be sustained by conventional sparging. The same batch is run using MBD. Reasonably good growth patterns are observed. DO levels are well above 70% for most of the time during operation. High oxygen demand which can not be sustained by conventional sparging alone can be sustained by MBD. In this way in high den- sity cultures utilization of MBD can be a good alternative to fulfill required oxygen demand in fermentation.

The methylotrophic yeast Pichia pastoris is widely used for recombinant protein production due to its ability to grow to high cell densities as well as possession of an inducible methanol utilization pathway (MUT). The expression of genes encoding enzymes of the MUT pathway is very tightly regulated. These genes are turned on when methanol but not glucose is used as the sole carbon source. Thus, P. pastoris cells can be grown to high densities in glucose containing medium and expression of genes of MUT pathway can be turned on by changing the carbon source to methanol. This strategy is widely used for recombinant protein production wherein the gene of interest is cloned downstream of the methanol-inducible promoter of the gene encoding the first enzyme of the MUT pathway, alcohol oxidase I (AOXI). Despite production of a large number of recombinant proteins using the AOXI promoter, the mechanism of transcriptional activation of AOXI is not very well understood. It is only recently that a zinc finger protein known as Mxr1p (methanol expression regulator 1) was shown to play a key role in the regulation of AOXI as well as other genes of methanol utilization pathway (1) P. pastoris strains that do not express Mxr1p (mxr1) are unable to grow on peroxisomal substrates such as methanol and oleic acid. Methanol-inducible expression of genes involved in MUT pathway as well as those involved in peroxisome biogenesis (peroxins,) is severely impaired in mxr1 strains. While Mxr1p is constitutively expressed in cells cultured on glucose as well as methanol, it is cytosolic in glucose-grown cells, but nuclear in methanol-grown cells (1). The exact nucleotide sequence to which Mxr1p binds and regulates the expression of genes of MUT pathway is not known. The aim of this thesis is to map the Mxr1p binding sites in the promoters of methanol-inducible genes of P. pastoris. As a first step towards understanding the mechanism of transcriptional regulation of AOXI and other methanol inducible genes of P. pastoris by Mxr1p, the N-terminal region comprising of 150 amino acids, including the zinc finger DNA binding domain of Mxr1p was cloned into an E. coli expression vector and the recombinant protein was purified from E. coli cells. This recombinant protein (referred to as Mxr1p in this study) was used in an electrophoretic mobility shift assay (EMSA) to identify Mxr1p binding sites in the AOXI promoter. EMSA was carried out with sixteen different oligonucleotides spanning AOXI promoter region between -940 and -114 bp. Such studies led to the identification of six Mxr1p binding sites in AOXI promoter. Using a combination of DNase I footprinting as well as EMSA with chimeric double stranded oligonucleotides, the minimal Mxr1p binding site was identified as a 20 bp DNA sequence containing a core 5’CYCC 3’ sequence. Using methylation interference as well as extensive mutagenesis studies, nucleotides critical for Mxr1p binding were identified. Comparative analysis of Mxr1p binding sites identified in our study with the AOXI promoter deletion studies of Hartner et al (2) suggested that the Mxr1p binding sites identified in our study are likely to function as methanol-inducible enhancers in vivo, since deletion of AOXI promoter regions comprising Mxr1p binding sites results in a significant loss of methanol-inducible promoter activity. Thus, Mxr1p binding sites are likely to function as Mxr1p response elements (MXREs) in vivo. Mxr1p is considered to be the P. pastoris homologue of S. cerevisiae Adr1p (alcohol dehydrogenase II [ADH2] synthesis regulator). Adr1p is a key regulator of S. cerevisiae genes involved in the metabolism of glycerol, ethanol and oleic acid. The DNA binding domains of Adr1p and Mxr1p share 82% similarity and 70% identity. We therefore examined whether Mxr1p can bind to the Adr1p binding site of ADH2 promoter(ADH2-UAS1). Our studies indicate that Mxr1p does not bind to ADH2-UAS1. Interestingly, a single point mutation restores Mxr1p binding to ADH2-UAS1. Since Mxr1p is involved in the regulation of a number of genes including AOXI, we examined whether promoters of other Mxr1p-regulated genes also harbour MXREs similar to those identified in AOXI promoter. The promoters of genes encoding dihydroxyacetone synthase (DHAS) and peroxin 8 (PEX8) were chosen for this purpose. A detailed analysis of Mxr1p binding to these promoter sequences led to the conclusion that DHAS and PEX8 promoters also harbour Mxr1p binding sites similar to those of AOXI promoter. Based on these studies, we have derived a consensus sequence for Mxr1p binding. This study is the first report on detailed characterization of Mxr1p binding sites in three methanol-inducible promoters of P. pastoris and thus provides the molecular framework by which this transcription factor functions as a master regulator of genes involved in methanol utilization pathway of P. pastoris. Our study provides the blue print for mapping Mxr1p binding sites in the promoters of other Mxr1p-regulated genes.

<p>The aim of this work was to develop a production process for the enzyme xyloglucan <i>endo</i>-transglycosylase from <i>Populus tremula x tremuloides</i> (<i>Ptt</i>XET16-34). The natural transglycosylating activity of this enzyme has previously been employed in a XET-Technology. This chemo enzymatic method is useful for biomimetic modification of cellulose surfaces and holds great potential for industrial applications. Thus, it requires that the XET-enzyme can be produced in larger scale.</p><p>This work also shows how the wildtype <i>Ptt</i>XET16-34 was modified into a glycosynthase. By mutation of the catalytic nucleophile into an alanine, glycine or serine residue, enzymes capable of synthesising defined xyloglucan fragments were obtained. These defined compounds are very valuable for further detailed studies of xyloglucan active-enzymes, but are also useful in molecular studies of the structurally important xyloglucan-cellulose interaction.</p><p>A heterologous production system for <i>Ptt</i>XET16-34 was previously developed in the methylotrophic yeast Pichia pastoris. A methanol-limited fed-batch process was also previously established, but the yield of active XET was low due to proteolysis problems and low productivity. Therefore, two alternative fed-batch techniques were investigated for the production of <i>Ptt</i>XET16-34: a temperature-limited fed-batch (TLFB) and an oxygen-limited high-pressure fed-batch (OLHPFB).</p><p>For the initial recovery of XET after the fermentation process, two different downstream processes were investigated: expanded bed adsorption (EBA) and cross-flow filtration (CFF).</p>

Grundlage der vorliegenden Arbeit ist die Überlegung, dass eine Möglichkeit, die Spezifität der bisher angewendeten Verfahren zur West-Nil-Virus-Diagnostik zu verbessern, in der Anwendung rekombinanter WNV-spezifischer Antigene besteht. Die unter anderem auf bioinformatischen Methoden basierende Identifikation von potenziellen B-Zell-Epitopen und Auswahl entsprechender Sequenzabschnitte richtete sich dabei gezielt auf immunogene Bereiche, die innerhalb der Gruppe der Flaviviren einen ausreichenden Sequenzunterschied zu allen weiteren sequenzverwandten Erregern, zusammengefasst im Japanische Enzephalitis-Serokomplex, boten. Drei ausgewählte Bereiche innerhalb der Strukturproteinsequenz, bezeichnet als prM, Cnat und Cme, sollten mit Hilfe des Expressionssystems Pichia pastoris bzw. Escherichia coli rekombinant exprimiert werden. Nach Erarbeitung optimaler Expressionsbedingungen folgte die affinitätschromatografische Reinigung der im weiteren Verlauf zur Immunisierung von Balb/c-Mäusen eingesetzten Polypeptide. Die gewonnenen Seren der nach verschiedenen Immunisierungsprotokollen geimpften Mäuse wurden im Anschluss immunologisch untersucht. Es zeigte sich, dass die rekombinanten Derivate des Capsid-Proteins eine deutliche Serokonversion hervorriefen. Analysen der mit Cnat und MBP-Cme immunisierten Mausseren wiesen vorhandene peptidspezifische sowie virusspezifische Antikörper nach. Der Einsatz dieser gewonnenen Peptidantigene im indirekten ELISA-Testsystem zur Detektion WNV-spezifischer Antikörper unter Verwendung humaner WNV-IgG-positiver Serumproben zeigte positive Resultate. Im Gegensatz hierzu führte die Immunisierung mit prM lediglich zu einer unspezifischen murinen Antikörperbildung. Die Unterscheidung zwischen WNV-positiven und WNV negativen Humanseren war unter Verwendung des rekombinanten Antigens prM nicht möglich. Im Ergebnis zeigten zwei der drei in dieser Arbeit rekombinant erstellten Strukturproteinabschnitte ihr immunologisches Potenzial in der Generierung muriner WNV spezifischer Antikörper. Zudem konnte mit der Expression der WNV-spezifischen C Protein Antigene ein Beitrag zur Etablierung eines indirekten ELISA-Testsystems zur Detektion WNV-bedingter Humaninfektionen geleistet werden.

Mucopolysaccharidosis (MPS) IIIB is an autosomal recessive disorder caused by a defect in alpha-N-acetylglucosaminidase (NAGLU), a lysosomal enzyme involved in the degradation of heparan sulphate. Dysfunctional NAGLU gives rise to a clinical phenotype of severe and progressive mental retardation, often accompanied by hyperactivity and aggressive behaviour. At present, there is no effective treatment for MPS IIIB. However, cloning of the human NAGLU cDNA has made the potential production of human recombinant enzyme for use in enzyme replacement therapy (ERT) a viable option. The work outlined herein focuses on attempts to produce human recombinant NAGLU (rNAGLU) using both yeast and insect cell based expression systems; with the major focus on yeast based expression. Use of a humanized yeast strain, codon optimisation of a portion of the NAGLU gene, selection of Mut+, MutS and multiple integrant strains, and growth at decreased temperature were explored to optimise NAGLU expression in the methylotrophic yeast, Pichia pastoris. As none of these measures resulted in abundant NAGLU production, Sf9 and Tni insect cell lines were investigated as an alternate expression system. Additionally, a protein transduction domain (PTD) was fused to NAGLU (NTAT) to circumvent current problems faced in delivering therapeutic enzymes to the brain. NAGLU protein, with and without a fused PTD, were expressed using stable transfection and baculovirus infection techniques. Small scale experiments utilizing the baculovirus expression vector system (BEVS) have yielded promising results, generating functionally active NAGLU and NTAT protein of the expected approximately 80-85 kDa molecular mass. This preliminary success indicates the BEVS may be an attractive option for the large scale production of rNAGLU and rNTAT.