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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Start-specific transcriptional regulation of the budding yeast cell cycle

Talbot, Craig January 1999 (has links)
No description available.
2

Estudo da biorredução de compostos carbonílicos por linhagens de Saccharomyces cerevisiae sp. /

Vieira, Marla Regina, Wendhausen Júnior, Renato, Universidade Regional de Blumenau. Programa de Pós-Graduação em Química. January 2006 (has links) (PDF)
Orientador: Renato Wendhausen Júnior. / Dissertação (mestrado) - Universidade Regional de Blumenau, Centro de Ciências Exatas e Naturais, Programa de Pós-Graduação em Química.
3

Biorredução da 4-aminoacetofenona catalisada por células de Saccharomyces cerevisiae sp. em sistemas bifásicos /

Lehmkuhl, Ana Lúcia, Wendhausen Júnior, Renato, Universidade Regional de Blumenau. Programa de Pós-Graduação em Química. January 2006 (has links) (PDF)
Orientador: Renato Wendhausen Júnior. / Dissertação (mestrado) - Universidade Regional de Blumenau, Centro de Ciências Exatas e Naturais, Programa de Pós-Graduação em Química.
4

Functional aspects of inorganic phosphate transport

Andersson, Michael R. January 2012 (has links)
Inorganic phosphate is an essential nutrient for all organisms. It is required for many cellular components as nucleic acids and phospholipids, and as energy-carrying compounds such as ATP. Thus, a regulated uptake of this pivotal nutrient is of outermost importance. Depending of the availability of phosphate in the surroundings the yeast Saccharomyces cerevisiae make use of two different systems for transporting phosphate into the interior of the cell: a low-affinity system that is active during surplus phosphate conditions and a high-affinity system that is active when the availability becomes limited. This thesis focuses on the high-affinity system, which is comprised of the Pho84 and Pho89 transporters. Of the two transporters, Pho84 is the predominant one, responsible for almost all phosphate uptake during low phosphate conditions, and the contribution of Pho89 is of minor importance. Hence Pho84 is by far the most well characterized phosphate transporter. Even though much is known about phosphate transporters in yeast little in known about how phosphate is transported. The work in this thesis aims to broaden the knowledge about the transport mechanism by the means of site-directed mutagenesis and functional characterization. Also the similarity of Pho84 to glucose sensors and the potential role of conserved residues in phosphate signaling are investigated. By the use of a high-affinity system deletion strain (∆Pho84 ∆Pho89), we also managed to investigate the functional importance of well conserved residues in Pho89. In summary: the work presented in this thesis has contributed to increase the knowledge about transport mechanisms in phosphate transporters.
5

Papel da trealose na proteção durante o estresse oxidativo causado por cádmio e a resposta adaptativa a este estresse em Saccharomyces Cerevisiae

Luciana Mara Costa Moreira 18 June 2007 (has links)
A poluição por metais pesados é um dos mais sérios problemas ambientais da atualidade devido tanto ao aumento de sua aplicação, como de sua natureza imutável. A importância em se estudar os metais, deve-se aos seus intensos efeitos tóxicos para o homem e todos os outros seres vivos. O cádmio é um metal não essencial e representa um grande potencial de danos a seres humanos e ao meio ambiente. A trealose é um dissacarídeo que participa como protetor em microrganismos em diferentes condições de estresses. Neste trabalho foi analisada a influência da trealose em resposta ao estresse oxidativo induzido pelo cádmio em linhagens de Saccharomyces cerevisiae. As linhagens utilizadas neste estudo são deficientes em genes importantes no metabolismo de trealose, na síntese (S. cerevisaie tps1) e na degradação (S. cerevisaie nth1) do dissacarídeo, desta forma foi possível analisar o papel da trealose frente ao estresse induzido pelo cádmio. Inicialmente, analisou-se o crescimento das linhagens em meio líquido com diferentes concentrações de cádmio, onde observou-se inibição no crescimento. A tolerância ao CdCl2 foi realizada através do plaqueamento, verificou-se que não existe formação de colônias em concentração superior a 25ppm. A incorporação de cádmio é maior quando foram usadas células viáveis coletadas na fase logarítmica. A linhagem tps1 possui uma incorporação de cádmio 3 vezes menor quando comparada às demais linhagens. A adição de glutationa reduzida ao meio extracelular não provocou alteração de incorporação de cádmio, porém ao adicionarmos aminoácidos (que formam a glutationa) ocorreu diminuição da incorporação em todas as linhagens. Quanto a formação de radicais livres intracelulares obtivemos que a linhagem tps1, possui um alto nível de oxidação celular mesmo na condição sem cádmio e quando exposta ao mesmo, apresentou um aumento na oxidação apesar de uma incorporação menor do metal que as demais linhagens. Análise da peroxidação lipídica realizada antes e após exposição das células ao cádmio, mostraram danos aos lipídeos. Observamos que células da linhagem nth1 (excesso de trealose) também sofrem esses danos, ou seja, a presença de um excesso de trealose não impediu a presença de danos aos lipídeos. Células da linhagem tps1 apresentaram maior dano lipídico que as demais linhagens evidenciando que, a ausência da trealose deixa os lipídeos mais susceptíveis a alterações deletérias. Procedeu-se também a análise da carbonilação de proteína onde observamos que na presença de cádmio não ocorreu carbonilação de proteínas, apenas a linhagem nth1 na concentração de 800ppm apresentou proteínas carboniladas, fato este relacionado a grande quantidade de radicais livres formados. As três linhagens após exposição à concentração de 50ppm de cádmio, apresentaram um aumento nos níveis de resíduos sulfidrílicos enquanto que na concentração de 800ppm apresentaram queda dos resíduos sulfidrílicos. Os resultados apresentados neste trabalho ajudaram a compreender o papel da trealose em células de S. cerevisiae frente ao estresse causado pelo cloreto de cádmio. / Pollution with heavy metals is one of the most serious environmental problems nowadays, which had in such a way to the increase of its application as, of its imutable nature. The importance of studying metals is directly related to intensive toxic effects to all living beings in our world. Cadmium is a non essential metal and represents a great danger to the human beings and also to the environmental. Trehalose is a disaccharide that participates as a protector in different conditions of stress. In this work the influence of trehalose in oxidative stress induced by cadmium was analyzed in different strains of Saccharomyces cerevisiae. The strains used in this study were not effective in important genes of the metabolism of trehalose, in the synthesis (S. cerevisaie tps1) and also in the degradation (S. cerevisaie nth1), so it was possible to analyze the performance of the trehalose in relation to the stress induced for cadmium. Initially the growth with different cadmium concentrations in medium liquid was analyzed, and the growth inhibition was observed. The tolerance to the CdCl2 was carried out by the growth on plates and one could observe that the formation was not present in concentrations up to 25ppm. Cells collected in the logarithmic phase had bigger cadmium incorporation. The strains tps1 presented a lower cadmium incorporation (3 times) when compared with other strains. The addition of reduced glutathione to the extracellular did not cause any alteration of in the cadmium incorporation, however, by adding amino acids, the ones which form glutathione, a reduction of the cadmium incorporation in all the strains occurred. The tps1 strains showed high level of cellular oxidation in control condition (without cadmium), and the cadmium incorporation showed an increase in the oxidation.Analyses of the lipid peroxidation carried out before and after exposition of the cells to cadmium showed damages to the lipids. We observe that cells of the strain nth1 (excess of trehalose) also suffer these damages. The presence of an excess of trehalose protected the lipids. Cells of the strain tps1 presented greater lipidic damage than the other strains, making clear that the absence of trehalose make the lipids more probable to have deleterious alterations. It was also performed a protein carbonilation analysis at cadmium presence and it did not induce a carbonilation of proteins. The stains nth1, whose concentration was 800ppm, presented carbonilated protein due to the high levels of ROS. The three strains after the exposition of 50ppm of cadmium showed an increase while on the concentration of 800ppm, it presented a drop on the levels of sulphydryl residues. The results presented in this work helped to understand the role of trehalose on Saccharomyces cerevisiae cells during cadmium stress.
6

Tillförsel av jäst till SSF i industriell skala / Supply of yeast for SSF on industrial scale

Boström, Karin January 2011 (has links)
Användning av etanol som drivmedel och en efterfråga på gröna kemikalier driver utvecklingen av bioetanol framåt. Etanolpiloten, SEKAB, i Örnsköldsvik är en av få anläggningar i världen med kompetens och kunskap att producera bioetanol baserat på lignocellulosa. På senare tid har det dock uppstått problem vid etanolframställningen på grund av att en del jästodlingar blivit kontaminerade av bakterier vilket lett till ett sämre utbyte av biomassa och etanol. Det huvudsakliga syftet med detta examensarbete var att ta reda på orsaken till dessa misslyckade jästodlingar.   Examensarbetet delades upp i två huvudsakliga problemområden. Förutom orsaken till de kontaminerade odlingarna studerades även funktionen hos en ny jäststam, Saccaromyces cerevisiae torrjäst, i syfte att undersöka om det finns bättre alternativ till den jäststam som används i etanopiloten i nuläget.   En specialstudie av rengöringen av odlingstankar och ledningar i etanolpiloten utfördes i syfte att kartlägga var i utrustningen som infektionsrisken är som störst. Försöken påvisade att det huvudsakliga problemet kan lokaliseras till den största jästodlingstanken. Där befinner sig jästen under en längre tid i en miljö som är gynnsam för tillväxt av både jäst och bakterier. En annan orsak till de infekterade odlingarna är att rengöringen av utrustningen inte har skett på rätt sätt, samt att temperaturen hos tvättkemikalierna har varit för låg. En viktig slutsats är därför att bättre rutiner vid hanteringen av jästodlingsutrustningen samt att större noggrannhet i samband med rengöringen bör eftersträvas.   En bidragande orsak till de infekterade odlingarna kan också härröra från uppodlingsprocessen av ympjäst som i dagens läge sker på laboratorium. Genom att använda en stam av S. cerevisiae som köps in i frystorkad form kan flera steg i jästodlingsprocessen elimineras. Det både förkortar odlingsprocessen och minskar infektionsrisken. S. cerevisiae torrjäst undersöktes både i laboratorium och i etanolpiloten. Tre olika odlingsskalor användes, skakflaskor (250 ml), labfermentorer (3 l) och pilotskala (10m3). Försöken påvisar höga utbyten av både biomassa och etanol. För att kunna hålla nere produktionskostnaderna för etanolframställningen är det viktigt att jästen som används går att odla på det hydrolysat som produceras vid förbehandlingen av råvaran. Försök i pilotskala visar på lovande resultat vid uppodling av S. cerevisiae torrjäst när hela 70 % av sockerkällan kommer från hydrolysat. Ytterligare utvärdering och optimering av odlingsprocessen samt en ekonomisk jämförelse mellan de tillgängliga jäststammarna krävs dock innan S. cerevisiae torrjäst eventuellt kan användas kontinuerligt i pilotskala.
7

Phytoestrogens in Two Dioecious Species: Isolation, Characterization and Role in Plant Reproduction

Maier, Camelia G. A. (Camelia Gabriela-Anca) 05 1900 (has links)
A highly specific steroid regulated transcription system system in Saccharomyces cerevisae was used to screen for phytoestrogens indioecious plants. Yeast cells were co-transformed with a human estrogen receptor expression plasmid and a reporter plasmid containing the E. coli β-galactosidase gene.
8

Proteome Profiling of Saccharomyces cerevisae stress response to Cumene Hydroperoxide (CHP)

Tuli, Leepika 09 September 2008 (has links)
Oxidative stress, described as the state of disturbed intracellular redox balance, has been associated with several human conditions including ageing, apoptosis, cancer, autoimmune and neuro-degenerative diseases. Stress studies have shown that reactive oxygen species (ROS) and reactive nitrogen species (RNS) along with its intermediates can attack essential cell targets such as: DNA, proteins, lipids and carbohydrates, leaving behind dysfunctional biologic molecules. In effect, a cell's primary response is to involve several defense mechanisms that are under a complex and intricate regulatory control to repair any damages that may have occurred. Although several stress studies have been conducted in the past that have approached this biologically complex process step by step, application of a Systems Biology towards a comprehensive understanding is still emerging. The current objective of this project is to identify proteins that change in response to cumene hydroperxoide (CHP) treatment and in parallel make an attempt to uncover events and processes that are a part of CHP-induced oxidative stress response. From a systems biology viewpoint, the Yeast Oxidative Stress project will monitor response at three different levels: transcriptomics, proteomics and metabolomics, with dynamic changes being measured from 3 to 120 min after CHP addition. Data collected from the different levels will be integrated to accomplish a holistic viewpoint of stress response in the given system and to develop mathematical tools for modeling biochemical networks. Saccharomyces cerevisiae was chosen as a model, based on its availability of a completely mapped genome sequence with a collection of null mutants that was relevant to our fundamental research of stress response mechanism. Yeast, a simple unicellular eukaryote has been extensively used for applied studies and has proven to be indispensable for stress research. Information derived from this project can reveal response mechanisms used by higher eukaryotes, especially if via analogous signaling cascades that are comparable between organisms. Current research investigates an optimal workflow for generating 2D gel based protein expression data and identifying proteins that are induced by cumene hydroperoxide treatment. A non-targeted protein profiling followed by a 2-way ANOVA analysis provided a list of proteins that differ significantly between treatments. Protein identification provided relevant information on which proteins are affected by CHP induced stress response, including posttranslational modifications of peroxiredoxins. Redox active protein, Ahp1, was regulated post-translationally with sulfonic acid modification observed for its active Cys(62) residue. / Ph. D.
9

Ação antiagregante e moduladora da função vascular da β-glucana extraída de Saccharomyces cerevisae e da forma carboximetilada derivada

Bezerra, Lorena Soares 01 April 2016 (has links)
Submitted by Maike Costa (maiksebas@gmail.com) on 2017-01-31T12:37:20Z No. of bitstreams: 1 arquivototal.pdf: 2719783 bytes, checksum: 00456e5b8ca69f853baec641a28cd6f2 (MD5) / Made available in DSpace on 2017-01-31T12:37:20Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2719783 bytes, checksum: 00456e5b8ca69f853baec641a28cd6f2 (MD5) Previous issue date: 2016-04-01 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / The β-D-glucans are polysaccharides constituting the cell wall of yeasts such as Saccharomyces cerevisiae. Evidence shows polymers have several beneficial effects, mainly related to immunomodulation. However, their action on platelet and endothelial function is understudied. This study aimed to evaluate the effect of (1-3) (1-6) β-D-glucan extracted from S. cerevisiae and derivative carboxymethylated (CM-G) on vascular and platelet function in rats. The animals were treated orally with CM-G and BG-Sc at a dose of 20 mg/kg daily for eight days and the controls received saline as placebo. At end, were collected blood and thoracic aortic artery to study platelet activation and aggregation by light transmission, flow cytometry, vascular reactivity and cytokine assay. In vitro studies of platelet activation and aggregation induced by adenosine diphosphate (ADP) and collagen were conducted with CM-G at different concentrations (100 and 300 μg/mL). Significant reduction in IL-8 levels (4,18 ± 0,72 pg/mL) in the group treated with CM-G was also found when compared to control (22,7 ± 6,9 pg/mL) and the BG-Sc group (16,4 ± 2,4 pg/mL). The reactivity studies shows BG-Sc and CM-G had no influence on vascular response to phenylephrine (PHE) compared to the control. In the group treated with BG-SC, the response to vasorelaxantes agents such as acetylcholine (ACH; Emax = 90,2 ± 14,1%; pD2 = 6,36 ± 0,30 M) and sodium nitroprusside (SNP; Emax = 92,3 ± 2,4%; pD2 = 10,21 ± 0,10M) were impaired compared to controls (ACH: Emax = 100 ± 7,5%; pD2 = 8,17 ± 0,25 M; SNP: Emax = 100 ± 9,5%; pD2 = 11,18 ± 0,27 M). However, treatment with CM-G (max = 93,1 ± 2,7%; pD2 = 11,71 ± 0,07 M) increased the potency of NPS when compared with the control (Emax = 100 ± 9.5%; pD2 = 11.18 ± 0.27). In vitro studies of platelet aggregation by light transmission reveals CM-G inhibited the aggregation stimulated by ADP in doses of 100 and 300 mg/ml, reaching 25,7 ± 2,7% and 14,8 ± 3,2% of aggregation, respectively. When aggregation was induced by collagen, only the dose 300 mg/ml had inhibitory activity (33 ± 6,2%). The antiplatelet effect was similar to acetylsalicylic acid when the aggregation was generate by ADP. Aggregation inhibition was also demonstrated by flow cytometry, however was observed that CM-G had no effect on platelet activation. In treated animals, there was inhibition of platelet aggregation induced by ADP (45% ± 3,9 and 45 ± 6%, respectively). However, when induced by collagen, antiplatelet effect was observed only in animals receiving the BG-Sc (22,6 ± 7,7%). The treatment and in vitro aggregation assays suggest that CM-G appears to be more selective for ADP. The findings indicate the CM-G and BG-Sc feature antiplatelet effect and modulating vascular function. Thus, the use of these polysaccharides may be a possible tool for the prevention of cardiovascular diseases / As β-D-glucanas são polissacarídeos constituintes da parede celular de leveduras, como a Saccharomyces Cerevisae. Evidências mostram que esses polímeros possuem diversos efeitos benéficos, principalmente relacionados a imunomodulação. Entretanto, a sua ação sobre a função plaquetária e endotelial é pouco estudada. Assim, este estudo teve como objetivo avaliar o efeito da (1-3) (1-6) β-d-glucana extraída de S. cerevisae e do seu derivado carboximetilado (CM-G) sobre a função vascular e plaquetária em ratos. Os animais foram tratados por via oral com CM-G e BG-Sc na dose de 20 mg/Kg, diariamente, durante oito dias, e os controles receberam solução salina como placebo. Ao final, foram coletados o sangue e a artéria aorta torácica para estudos de agregação e ativação plaquetária por transmissão luminosa, citometria de fluxo, reatividade vascular e dosagem de citocinas. Foram realizados estudos in vitro de agregação e ativação plaquetária induzida por adenosina difosfato (ADP) e colágeno com a CM-G em diferentes concentrações (100 e 300 μg/mL). Constatou-se redução significativa dos níveis de IL-8 (4,18±0,72 pg/mL) no grupo tratado com CM-G ao se comparar com o grupo controle (22,7±6,9 pg/mL) e com o grupo BG-Sc (16,4±2,4 pg/mL). Os estudos de reatividade mostraram que a BG-Sc e a CM-G não exerceram influência sobre a resposta vascular da fenilefrina (PHE) em relação ao controle. No grupo tratado com BG-SC, a resposta aos agentes vasorelaxantes acetilcolina (ACH; Emax = 90,2 ± 14,1%; pD2 = 6,36 ± 0,30 M) e nitroprussiato de sódio (NPS; Emax = 92,3± 2,4%; pD2 = 10,21 ± 0,10M) foram prejudicadas em relação aos controles (ACH: Emax = 100 ± 7,5%; pD2 = 8,17 ± 0,25 M; NPS: Emax = 100 ± 9,5%; pD2 = 11,18 ± 0,27 M). Porém, o tratamento com a CM-G (Emax = 93,1 ± 2,7 %; pD2 = 11,71 ± 0,07 M) aumentou a potência do NPS quando comparado com o controle (Emax = 100 ± 9,5%; pD2 = 11,18 ± 0,27 M). Os estudos de agregação plaquetária in vitro por transmissão luminosa revelam que a CM-G inibiu a agregação estimulada por ADP nas doses de 100 e 300 μg/mL, atingindo 25.7±2.7% e 14.8±3.2% de agregação, respectivamente. Quando a agregação foi induzida pelo colágeno, apenas a dose 300 μg/mL teve ação inibitória (33 ± 6,2%). O efeito antiagregante foi similar ao ácido acetilsalicílico quando a agregação foi induzida por ADP. Inibição da agregação também foi demonstrada na técnica de citometria de fluxo, porém observou-se que a CM-G não afetou a ativação plaquetária. Nos animais tratados, verificou-se inibição da agregação plaquetária induzida por ADP (45 ± 3.9% e 45 ± 6 %, respectivamente). Entretanto, quando induzido por colágeno, o efeito antiagregante foi visto apenas nos animais que receberam BG-Sc (22.6 ± 7.7%). O tratamento e os ensaios de agregação in vitro sugerem que a CM-G parece ser mais seletiva para o ADP. Os achados indicam que a CM-G e a BG-Sc apresentam efeito antiagregante e moduladora da função vascular. Assim, o uso desses polissacarídeos pode ser uma possível ferramenta para a prevenção de doenças cardiovasculares.
10

Expression of mannanases in fermentative yeasts.

Fouche, Nicolette 03 1900 (has links)
Thesis (MSc (Microbiology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The search for a cost-effective, environmentally friendly replacement for fossil fuels resulted in bio-ethanol production receiving a lot of attention. Lignocellulose, is considered to be the most abundant renewable source on earth, and consists of cellulose, hemicellulose and lignin. Exploitation thereof as a substrate for ethanol production, can serve as solution in producing bio-ethanol as an adequate replacement for fossil fuels. Hemicelluloses, contributing up to a third of the lignocellulosic substrate, consists mainly of xylan and mannan and can be degraded by hemicellulolytic enzymes that are produced by plant cell wall degrading organisms. Galactoglucomannan is the most complex form of mannan and requires a consortium of enzymes for complete hydrolysis. These enzymes include β-mannanase, β-mannosidase, α-galactosidase, β-glucosidase and galactomannan acetylesterases. Saccharomyces cerevisiae is a well-known fermentative organism that has been used in various industrial processes and is able to produce ethanol from hexose sugars. Although this organism is unable to utilize complex lignocellulosic structures, DNA manipulation techniques and recombinant technology can be implemented to overcome this obstacle. Strains of S. cerevisiae pose other shortcomings like hyperglycosylation and therefore other non-conventional yeasts (such as Kluyveromyces lactis) are now also being considered for heterologous protein production. The mannanase gene (manI) of Aspergillus aculeatus was expressed in K. lactis GG799 and S. cerevisiae Y294. K. lactis transformants were stable for two weeks in consecutive subcultures and secreted a Man1 of 55 kDa. The recombinant Man1 displayed an optimum temperature of 70°C and a pH optimum of 5 when produced by K. lactis. Activity levels of about 160 – 180 nkat/ml was obtained after 86 hours of cultivation, which was similar to the activity observed with S. cerevisiae under the same conditions. Disruption of the ku80 gene did not contribute to the stability of the cultures and a heterogeneous culture developed for 10 days of consecutive subculturing. The mannosidase gene (man1) from A. niger and mannanase gene (manI) from A. aculeatus were constitutively expressed in S. cerevisiae Y294 and S. cerevisiae NI-C-D4. The MndA and Man1 proteins appeared as a 140 kDa and 58 kDa species on the SDS-PAGE analysis when expressed in S. cerevisiae Y294, respectively. MndA had an optimum temperature of 50°C and optimum pH 5. Man1 produced by S. cerevisiae Y294 indicated a pH optimum of 6 and temperature optimum of 70°C. The MndA displayed low levels of endomannanase activity and no β-mannosidase activity could be detected. Co-expression of man1 and mndA in either S. cerevisiae Y294 and S. cerevisiae NI-C-D4, resulted in less hydrolysis of galactoglucomannan. An increase in the size of the plasmid generally results in a decrease in the copy number, leading to a decrease in the amount of ManI protein being produced. The co-expression of ManI and MndA could also have resulted in a higher metabolic burden on the cell, hence the amount of ManI are produced. This study confirms that more research should be done on the evaluation of alternative hosts for expression of foreign proteins. Furthermore, producing enzymes cocktails for industrial application should be considered rather than co-expression of various enzymes in one host. / AFRIKAANSE OPSOMMING: ‘n Behoefte na ‘n koste-effektiewe en omgewingsvriendelike vervoer brandstof is besig om toe te neem. Lignosellulose word beskou as die volopste hernubare bron vir biobrandstof en lignosellulose bestaan uit sellulose, hemisellulose en lignien. Die gebruik daarvan vir die produksie van bio-etanol kan ’n voldoende alternatief vir fossielbrandstowwe bied. Verbruik van lignosellulose as bron vir die produksie van biobrandstof bied ’n oplossing vir die energie krises. Hemisellulose vorm ’n derde van lignosellulose substraat en bestaan uit xilaan en mannaan en word deur hemisellolitiese ensieme afgebreek wat algemeen by plantselwand-verterende organismes voorkom. Galaktoglukomannaan is die mees komplekse vorm van mannaan en benodig verskeie ensieme vir volkome hidroliese. Hierdie ensieme sluit in β-mannanase, β-mannosidase, α-galaktosidase, β-glukosidase en galaktomanaan asetielesterases. Saccharomyces cerevisiae is ‘n bekende fermenterende organisme wat gereeld in verskeie industriële prosesse gebruik word en kan etanol van heksose suikers produseer. Die organisme beskik nie oor die vermoë om komplekse polisakkarides wat in lignosellulose voorkom te hidroliseer nie maar. DNS-manipuleringstegnieke en rekombinante tegnologie maak dit egter moontlik die probellm te oorbrug. S. cerevisiae het nogtans tekortkominge soos hiperglikosilering en daarom word ander nie-konvensionele giste (soos Kluyveromyces lactis) tans ook vir die produksie van rekombinante proteine ondersoek. Die mannanase geen (manI) vanaf Aspergillus aculeatus is in K. lactis GG799 en S. cerevisiae Y294 uitgedruk. K. lactis transformante was stabiel vir twee weke in opeenvolgende subkluture en het ‘n Man1 van 55 kDa geproduseer. Die rekombinante Man1 ensiem het ‘n temperatuur optimum van 70°C en pH optimum van 5.0 getoon in K. Lactis. Aktiwiteitsvlakke van 160 – 180 nkat/ml was bereik na 86 uur klutivering, In vergelyking met S. cerevisiae was aktiwiteitsvlakke eenders oor ‘n periode Die disrupsie van die ku80 geen het geen effek op die stabiliteit van die transformante in 10 dae opeenvolgende sub-kulture getoon nie. Die mannosidase geen (mndA) vanaf Aspergillus niger en die mannanase geen (man1) van Aspergillus aculeatus is konstitutief in S. cerevisiae Y294 en S. cerevisiae NI-C-D4 uitgedruk. Uitdrukking van die MndA en Man1 proteïen in S. cerevisiae Y294 het onderskeidelik ‘n 140 kDa en 58 kDa spesie getoon met SDS-PAGE analisering. Die MndA ensiem het ‘n temperatuur optimum van 50°C and pH optimum van 5.0 getoon. Man1 het ‘n pH optimum van 6.0 en ‘n temperatuur optimum van 70°C getoon. MndA het lae hidrolitiese aktiwiteit op galaktoglukomannaan, maar geen β-mannosidase aktiwiteit getoon nie. Wanneer man1 and mndA saam in S. cerevisiae Y294 en S. cerevisiae NI-C-D4 uitgedruk is, het die hidroliese van galaktoglukomannan dramaties afgeneem. ‘n Toename in die grootte van ‘n plasmied veroorsaak dikwels ‘n afname in kopiegetal wat die produksie van ManI verlaag. Die ko-uitdrukking van ManI en MndA kan ook tot ’n hoër metaboliese las lei en dus die laer produksie van ManI. Resultate in hierdie studie wys daarop dat meer navorsing benodig word in die soeke na alternatiewe gashere vir uitdrukking van mannanases. Ensiem mengsels vir industriële toepassings behoort eerder gebruik te word as die ko-ekspressie van verskeie ensieme in ’n enkel gasheer.

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