Made available in DSpace on 2014-06-12T15:55:13Z (GMT). No. of bitstreams: 2 arquivo9635_1.pdf: 3625171 bytes, checksum: 1af9e11b0a5c4759222495f08003d2d6 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2008 / Saccharomyces cerevisiae e Candida utilis apresentam interesse biotecnológico para produção de biomassa e outros bioingredientes em substratos alternativos. O objetivo deste trabalho foi a produção de biomassa, por cultivo submerso utilizando como substrato resíduos da carcinicultura e das indústrias sucroalcooleira. O resíduo de camarão foi tratado com diferentes taxas de diluição a 40 °C, e analisada ao longo de 5 horas em intervalos de 1 hora, atingindo os melhores resultados de hidrólise protéica na diluição 1:4. O cultivo das leveduras nesse resíduo mostrou que apenas a C. utilis se adaptou ao substrato, atingindo uma taxa de crescimento máximo (μmax) 0,10 h-1 no cultivo submerso em frasco Erlenmeyer sob agitação de 150 rpm, a 30 °C durante 48 horas. A C. utilis foi cultivada em melaço in natura nas concentrações 1%, 2%, 4%, 6%, 8% e 10% (p/v) como fonte alternativa de carbono, obtendo os melhores resultados na condição de 2%. Os experimentos de cultivo em batelada com um volume de trabalho de 1 L e 4 L foram conduzidos em biorreator (BioFlo2000, New Brunswick Scientific) a 30 ºC, taxa de aeração 1 vvm e velocidade de agitação 150 rpm utilizando o resíuo de camarão hidrolisado na diluição de 1:4 durante 3 horas com inclusão de 2% (p/v) de melaço. A C. utilis mostrou a maior produção de biomassa (9.90 g/L) em 48 h de cultivo, consumindo cerca de 75% da concentração inicial dos açucares redutores presentes no meio. Valores de μmax, rendimento da biomassa (Yx/s) e produtividade (QX) foram 0,20 h-1, 0,8 g/g e 0,53 g/L h, respectivamente. A biomassa seca apresentou valores nutricionais com baixa concentração de lipídeos (0,63 g/100g de biomassa) e alta concentração de proteína (61,60 g/100g de biomassa), além de energia metabolizável (316,09 Kcal/100g de biomassa) e minerais como cálcio e sódio. Desta forma é possível concluir que a levedura C. utilis apresenta potencial na single cell protein visando sua utilização na suplementação alimentar animal

A complete initial velocity study of the 6-phosphogluconate dehydrogenase from Candida utilis in both reaction directions suggests a rapid equilibrium random kinetic mechanism with dead-end E:NADP:(ribulose 5-phosphate) and E:NADPH:(6- phosphogluconate) complexes. Initial velocity studies obtained as a function of pH and using NAD as the dinucleotide substrate for the reaction suggest that the 2'-phosphate is critical for productive binding of the dinucleotide substrate. Primary deuterium isotope effects using 3-<i-6-phosphogluconate were obtained for the 6-phosphogluconate dehydrogenase reaction using NADP and various alternative inucleotide substrates.

Estudou-se a influência da concentração inicial de substrato no cultivo em fermentador para produção de biomassa de Candida utilis IZ-1840 em meio sintético tamponado contendo glicerol (1,2,3-propanotriol) como fonte exclusiva de carbono nas seguintes concentrações: 15, 25, 35, 45, 55, 65 e 75 g/L com ensaios em duplicata. Observou-se um comportamento cinético característico de fenômeno de inibição por substrato, tendo-se então ajustada uma equação de modelo de inibição baseada na literatura para os dados de velocidade específica máxima de crescimento celular em função da concentração inicial de substrato. A partir de tal equação determinou-se o valor da concentração inicial de substrato onde não ocorre inibição, definido como S* ( S*=17,511 g/L) e o valor teórico acima do qual a inibição é máxima definido como Sm, (Sm=175,4 g/L). O valor teórico de velocidade específica máxima de crescimento celular, definido como &#181;* correspondente ao valor S* como concentração de substrato inicial foi calculada em 0,225 1/h. / The influence of initial substrate concentration in the growth of Candida utilis IZ-1840 in a buffered synthetic mediurn was studied utilizing glycerol (1,2,3-propanetriol) as an exc1usive carbon source, in the following concentrations: 15, 25, 35, 45, 55, 65 and 75 of in double assays. Characteristic kinetic behavior of substrate inhibition was detected, then one model equation of inhibition based on literature was adjusted for the maximum specific growth rate in function of the initial substrate concentration. From this equation it was possible to determine the value of the initial substrate concentration that do not occur growth inhibition, defined as S* (S* = 17,511 g/L).and the theoretical value of limit concentration where above this the growth inhibition becomes maximum which was defined as Sm (Sm = 175,4 g/L). The theoretical value for maximum specific growth rate, defmed as &#181;* corresponding to determined S* as initial substrate concentration was calculated in 0,225 1/h.

Estudou-se a influência da concentração inicial de substrato no cultivo em fermentador para produção de biomassa de Candida utilis IZ-1840 em meio sintético tamponado contendo glicerol (1,2,3-propanotriol) como fonte exclusiva de carbono nas seguintes concentrações: 15, 25, 35, 45, 55, 65 e 75 g/L com ensaios em duplicata. Observou-se um comportamento cinético característico de fenômeno de inibição por substrato, tendo-se então ajustada uma equação de modelo de inibição baseada na literatura para os dados de velocidade específica máxima de crescimento celular em função da concentração inicial de substrato. A partir de tal equação determinou-se o valor da concentração inicial de substrato onde não ocorre inibição, definido como S* ( S*=17,511 g/L) e o valor teórico acima do qual a inibição é máxima definido como Sm, (Sm=175,4 g/L). O valor teórico de velocidade específica máxima de crescimento celular, definido como &#181;* correspondente ao valor S* como concentração de substrato inicial foi calculada em 0,225 1/h. / The influence of initial substrate concentration in the growth of Candida utilis IZ-1840 in a buffered synthetic mediurn was studied utilizing glycerol (1,2,3-propanetriol) as an exc1usive carbon source, in the following concentrations: 15, 25, 35, 45, 55, 65 and 75 of in double assays. Characteristic kinetic behavior of substrate inhibition was detected, then one model equation of inhibition based on literature was adjusted for the maximum specific growth rate in function of the initial substrate concentration. From this equation it was possible to determine the value of the initial substrate concentration that do not occur growth inhibition, defined as S* (S* = 17,511 g/L).and the theoretical value of limit concentration where above this the growth inhibition becomes maximum which was defined as Sm (Sm = 175,4 g/L). The theoretical value for maximum specific growth rate, defmed as &#181;* corresponding to determined S* as initial substrate concentration was calculated in 0,225 1/h.

Trensums Food AB är ett företag som producerar ett flertal olika livsmedelsprodukter åt flera globala varumärksägare. Några produkter som produceras av företaget är olika såser bl.a. BBQ-sås och vaniljsås. Genom att tillsätta syra i såserna så att pH blir &lt; 4,2 anses produkterna säkra. Uppdragsgivare till produkten menar att det är viktigt att använda ättiksyra istället för andra syror och att inte pH är helt avgörande för en säker produkt. Syftet med projektet var att undersöka hur effektiva olika organiska svaga syror är på att avdöda olika mikroorganismer i BBQ-sås och mjölkbaserad sås. Det som främst påverkar den antimikrobiella aktiviteten hos en syra är mängden odissocierad syra. Mängden odissocierad syra i produkten beror på syrans pKa-värde, totala halten av syran och det omgivande pH i produkten. pH mättes i produkterna för att se om pH är avgörande för avdödningen eller om det är valet av syra som är viktigast. Syrorna som undersöktes var ättiksyra, citronsyra och mjölksyra på mikroorganismerna Candida utilis, Bacillus subtilis och Enterococcus faecium. BBQ-sås och mjölkbaserad sås tillverkades i olika batcher med viktprocenten 0, 0,12, 0,24 samt 0,36 % av respektive syra. I varje prov ympades respektive mikroorganism till en uppskattad halt på ca 103 CFU/ml. Efter 5 dagars inkubation i rumstemperatur mättes halten CFU/ml. Ättiksyra var den syra som var effektivast både i BBQ-såsen och den mjölkbaserade såsen. I BBQ-såsen reducerade ättiksyra med samtliga viktprocent alla mikroorganismerna till under minsta detektionsgränsen (&lt; 101 CFU/ml). Citronsyra och mjölksyra reducerade enbart E.faecium och B.subtilis till under minsta detektionsgränsen. I den mjölkbaserade såsen som även var kontaminerad av andra mikroorganismer var det bara ättiksyra som synligt reducerade halten med ökad viktprocent syra. pH var lägre i BBQ-såsen med citronsyra och mjölksyra än med ättiksyra. Detta visar på att avdödningen av de undersökta mikroorganismerna inte bara är pH-beroende utan också påverkas av vilken syra som används. Den antimikrobiella aktiviteten beror på syrans pKa-värde och därmed mängden odissocierad syra. Ättiksyra har ett högre pKa-värde än både citronsyra och mjölksyra och befinner sig i högre utsträckning i odissocierad tillstånd än de övriga syrorna i båda produkterna. / Trensums Food AB is a company that produces a wide variety of food products to different global trademark owners. Some of the products produced by Trensums Food AB are different kind of sauces, including BBQ-sauce and vanilla sauce. The sauce products are considered safe when an acid is added resulting in a pH &lt; 4,2. The outsource of the company claims that it is important to use acetic acid instead of other kind of acids and that the pH is not crucial to consider the product safe. The goal of this project was to investigate how effectively different kind of organic acids work against microorganisms in the BBQ-sauce and milk-based sauce produced by Trensums Food AB. The main antimicrobial activity of an acid depends on its concentration of undissociated acid. Which further depends on the pKa-value of the acid and also the surrounding pH in the product. The pH was measured in the products to see if pH is critical for the antimicrobial activity or if the choice of acid is more important. The acids used in this project was acetic acid, citric acid and lactic acid and they were tested on Candida utilis, Bacillus subtilis and Enterococci faecium. BBQ-sauce and milk-based sauce were made in different batches containing 0, 0,12, 0,24 and 0,36 weight percent of respective acid. Each batch contained 103 CFU/ml of respective microorganism. After 5 days of incubation a viable count was performed. The acetic acid was the most effective acid in both type of sauces, reducing all microorganisms below the detection limit (&lt; 101 CFU/ml) in the BBQ-sauce within all batches. The citric acid and lactic acid reduced only E.faecium and B.subtilis to a value below the lowest level of detection. In the milk-based sauce, which was contaminated with additional microorganisms, it was only the acetic acid that showed an increasing effect of antimicrobial activity with increasing concentration of acid. The pH was lower in the BBQ-sauce when using citric acid and lactic acid compared to when using acetic acid. Thus concluding that the antimicrobial activity of the selected microorganisms is not solely dependent on the level of pH but additionally the type of acid being used. The acetic acid has a higher pKa-value compared to the other acids and is therefore to a higher extent in a undissociated state.

No description available.

Dissertation (PhD)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Yeast species differ remarkably in their ability to degrade extracellular dicarboxylic acids and to utilise them as their only source of carbon. The fission yeast Schizosaccharomyces pombe effectively degrades L-malate, but only in the presence of an assimilable carbon source. In contrast, the yeast Saccharomyces cerevisiae is unable to effectively degrade L-malate, which is ascribed to the slow uptake of L-malate by diffusion. In contrast, the yeast Candida utilis can utilise L-malate as the only source of carbon and energy, but this is subject to substrate induction and catabolite repression. Very little research has been done on a molecular level in C. utilis and only a few of its genes have been studied. In this study, we have shown that the yeast C. utilis effectively degraded extracellular L-malate and fumarate, but in the presence of glucose or other assimilable carbon sources, the transport and degradation of these dicarboxylic acids was repressed. The transport of both dicarboxylic acids was shown to be strongly inducible by either L-malate or fumarate and kinetic studies suggest that the same transporter protein transports the two dicarboxylic acids. In contrast, S. pombe effectively degraded extracellular L-malate, but not fumarate, only in the presence of glucose or other assimilable carbon sources. The S. pombe malate transporter was unable to transport fumarate, although fumarate inhibited the uptake of L-malate. In order to clone the C. utilis dicarboxylic acid transporter, a cDNA library from C. utilis was constructed using a number of strategies to ensure representativeness and high transformation frequencies. The cDNA library was transformed in a S. cerevisiae strain carrying a plasmid containing the S. pombe malic enzyme gene (mae2) to allow screening for a malate-degrading S. cerevisiae clone. However, no positive clones that would indicate the successful cloning of the C. utilis malate transporter were obtained. The C. utilis malic enzyme gene, CuME, was subsequently isolated from the cDNA library based on conserved sequence homologies with the genes of S. cerevisiae and S. pombe, and characterised on a molecular and biochemical level. Sequence analysis revealed an open reading frame of 1926 bp, encoding a 641 amino acid polypeptide with a predicted molecular weight of 70.2 kDa. The optimum temperature for the C. utilis malic enzyme was 52°C and the enzyme was stable at 50°C for 2 hours. The inferred amino acid sequence showed significant homology with the malic enzymes of S. pombe and S. cerevisiae. Expression of the CuME gene is subject to glucose repression and substrate induction, as was observed for the dicarboxylic acid transporter from C. utilis. The CuME gene was successfully coexpressed with the S. pombe malate permease gene (mae1), resulting in a recombinant strain of S. cerevisiae able to effectively degrade L-malate. / AFRIKAANSE OPSOMMING: Daar is ’n merkwaardige verskil in die vermoë van verskillende gisspesies om ektrasellulêre dikarboksielsure af te breek en dit as enigste bron van koolstof te benut. Die splitsingsgis Schizosaccharomyces pombe kan L-malaat effektief afbreek, maar slegs in die teenwoordigheid van ’n ander benutbare koolstofbron. In teenstelling hiermee is dit vir die gis Saccharomyces cerevisiae onmoontlik om L-malaat effektief af te breek en te benut, wat hoofsaaklik toegeskryf kan word aan die stadige opname van L-malaat deur middel van diffusie. Die gis Candida utilis kan egter L-malaat as die enigste bron van koolstof en energie benut, maar dit is onderhewig aan substraat-induksie en kataboliet onderdrukking. Baie min navorsing op molekulêre vlak is tot hede in C. utilis uitgevoer en slegs ’n paar gene in hierdie gis is al bestudeer. In hierdie studie het ons aangetoon dat die gis C. utilis L-malaat en fumaraat effektief afbreek, maar dat glukose of ander benutbare koolstofbronne die opname en afbraak van hierdie dikarboksielsure onderdruk. Die opname van beide dikarboksielsure is sterk induseerbaar deur L-malaat óf fumaraat, terwyl kinetiese studies toon dat beide dikarboksielsure deur dieselfde transporter-proteïen vervoer word. In teenstelling hiermee kan S. pombe ekstrasellulêre L-malaat, maar nie fumaraat nie, in die teenwoordigheid van glukose of ’n ander benutbare koolstofbron effektief afbreek. Die S. pombe L-malaat transporter was nie in staat om fumaraat te vervoer nie, alhoewel fumaraat die opname van L-malaat onderdruk het. Ten einde die dikarboksielsuur transporter van C. utilis te kloneer, is verskeie strategieë gevolg ten einde ’n cDNA-biblioteek van C. utilis te konstrueer wat verteenwoordiging en hoë transformasie-frekwensies kan verseker. Die cDNA-biblioteek is getransformeer in ’n S. cerevisiae ras wat die S. pombe malaatensiem geen (mae2) bevat om die sifting van ’n S. cerevisiae kloon wat malaat effektief kan afbreek, moontlik te maak. Geen positiewe klone wat dui op die klonering van die C. utilis malaat transporter kon egter gevind word nie. Die C. utilis malaatensiem geen, CuME, is vervolgens van uit die cDNA biblioteek geïsoleer deur van gekonserveerde DNA-homologie met S. cerevisiae en S. pombe gebruik te maak, en op molekulêre en biochemiese vlak gekarakteriseer. DNA-volgordebepaling het ’n oopleesraam van 1926 bp onthul, wat kodeer vir ’n 641 aminosuur polipeptied met ’n verwagte molekulêre gewig van 70.2 kDa. Die optimale temperatuur van die C. utilis malaatensiem was 52°C en die ensiem was vir 2 ure stabiel by 50°C. Die afgeleide aminosuurvolgorde het beduidende homologie met die malaatensieme van S. pombe en S. cerevisiae getoon. Die CuME geen is suksesvol saam met die S. pombe malaat permease geen (mae1) uitgedruk om ’n rekombinante S. cerevisiae ras te genereer wat in staat is om L-malaat effektief af te breek.