Thesis (MSc)--University of Stellenbosch, 2007. / Bibliography. Also available via the Internet.

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1. The inhibitory effect of glucosone on yeast fermentation was shown to the specific for the D-isomer, and exerted at some point before the breakdown of fructose-1:6-diphosphate. 2. The results of the fermentation experiments are analysed, kinetically, and glucosone shown to be a pseudo-irreversible inhibitor, of the type described by Ackermann and Potter (1949). It is shown that the effects produced by glucosone in animals can be correlated vd.th this finding. 3. The osone is shown to be phosphorylated by ATP in the presence of hexokinase. 4. It is suggested that the inhibitory effect produced by glucosone on yeast fermentation, is due to the slow dissociation of a glucosone phosphate from the hexokinase molecule. 5. The effect of hexokinase on a number of glucose analogues is reported, and indications are given of the high degree of specificity exhibited by the enzyme. 6. Methods are described for the preparation of an actively fermenting acetone-dried extract, and a maceration juice, from 'bakers' yeast. The preparation and some properties of cold-treated bakers' yeast are also described. 7. A method is described for the separation of the substrates .and products of the hexokinase reaction, on paper chromatograms.

The effects of essential oils (EO) and condensed tannin (CT) on methane production and fermentation were evaluated under in vitro conditions. Experiment one screened the effects of ten different EO at 500 mg/L of culture fluid on methane production in a 24 hr rumen batch culture. Based on the results from experiment one, four EO (clove oil (CLO), cinnamon oil (CNO), white thyme oil (WTO), and anise oil (ANO)) were selected and tested at three different dose levels (125, 250, and 500 mg/L of culture fluid) for their effects on methane production and fermentation in a 24 hr batch culture (experiment two). Methane production was significantly reduced with the four EO at the 500 mg/L dose but at 250 mg/L; only CLO and CNO reduced methane production. The reduction in methane production with the 500 mg/L dose was also associated with reductions in dry matter (DM) digestibility and total volatile fatty acids (VFA). In the third experiment, the effect of CT at 2.5, 5 and 7.5% of diet DM on methane production was also tested in a 24 hr batch culture. Results from this experiment showed no effect of CT on methane production although methane production tended to be lower at 7.5% CT. In conclusion, the reduction in methane production with EO most likely resulted from EO negative effects on DM digestibility and fermentation.

Resumo: Das sementes da mamona extrai-se o óleo de rícino, aplicado in natura ou em sua forma modificada nas áreas médica, farmacêutica e industrial. Um de seus derivados químicos - o Poliquilgerm® - evidencia propriedades antifúngicas sobre Candida albicans e bacteriostática/bactericida sobre Escherichia coli ao nível de 99,9%. Considerando-se estas propriedades aplicou-se o Poliquilgerm em culturas de Leuconostoc mesenteroides, uma bactéria contaminante freqüente dos mostos em indústrias sucro-alcooleiras. Esta bactéria quando contaminante de mostos produz além do ácido láctico a dextrana, um polímero de glicose de consistência gelatinosa que aumenta a viscosidade dos fluidos dos processos. Devido a estas características, no presente trabalho avaliou-se o efeito de diferentes concentrações do Poliquilgerm sobre a viscosidade de soluções de dextrana, bem como em culturas de L. mesenteroides. Analisando-se as soluções de dextrana em contato com o produto conclui-se que o Poliquilgerm® não induziu hidrólise nas ligações glicosídicas da dextrana. O produto nas concentrações de 1,0 e 0,2% inibiu o crescimento de L. mesenteroides alcançando até 100% em ambas as concentrações, evidenciado por quantificação da biomassa e confirmado mediante plaqueamento por técnica Pour Plate, onde a inibição foi de 98% na diminuição das UFC/mL após 24 horas em contato com 1,0% do produto. Em relação à viscosidade da cultura, verificou-se até 20,56% de diminuição quando utilizados 1,0% do produto. Em cultura mista (L. mesenteroides e S. cerevisiae), registrou-se até 6,8% de diminuição da viscosidade. Verificou-se que S. cerevisiae apresenta sensibilidade ao Poliquilgerm nas concentrações 1,0 e 0,2% apenas no tempo inicial, pois após 24 horas a cultura atinge o mesmo nível de crescimento do controle, adaptando-se à presença do produto...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Castor-oil, extracted from seeds of Ricinus communis L., is normally applied in natura or in its modified form in medical, pharmaceutical and industrial areas. One of its chemical derivates - the Poliquilgerm® - showed antifungal properties on Candida albicans, and bacteriostatic/bactericide ones on Escherichia coli reaching 99.9%. Considering these features, Poliquilgerm was applied in cultures of Leuconostoc mesenteroides, a frequent contaminant bacterium of musts on sugar and alcohol industries. This bacterium when contaminant of must produce beyond lactic acid the dextran, a polymer of glucose, with gelatinous consistency which may increase the operation fluids viscosity. Due to these characteristics, in the present study, the effect of different concentrations of Poliquilgerm on viscosity of dextran's solutions and on cultures of L. mesenteroides was evaluated. Analyzing the solutions of dextrana in contact with the product, it was concluded that it did not induce hydrolysis on glycosidic links. The product in concentrations of 1.0 and 0.2% inhibited the growth of L. mesenteroides reaching up to 100% in both concentrations, as evidenced by biomass quantification and confirmed by plating by Pour Plate technique, which inhibition was 98% of decrease in the CFU / mL after 24 hours in contact with 1.0% of the product. In relation to the culture viscosity, it was observed 20.56% of reduction when it was used 1.0% of the product. In mixed culture (L. mesenteroides and S. cerevisiae), it was registered up to 6.8% of decrease in viscosity. It was observed that S. Cerevisiae shows sensitivity to 1.0 and 0.2% concentrations of Poliquilgerm only at the initial time, because after 24 hours the culture reaches the same level of growth control, getting adaptated to the presence of the product. It was studied the Poliquilgerm hydrolytic activity on release of ART...(Complete abstract, click electronic access below) / Orientador: Dejanira de Franceschi de Angelis / Coorientador: Antonia Marli dos Santos / Banca: Salvador Claro Neto / Banca: Octavio Antonio Valsechi / Mestre

Made available in DSpace on 2014-06-11T19:23:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-02-22Bitstream added on 2014-06-13T19:08:55Z : No. of bitstreams: 1 silveira_ea_me_araiq.pdf: 555848 bytes, checksum: 89c80bc437beb0f21db690492633ec23 (MD5) / Para o aprimoramento do processo industrial de produção de bioetanol, é fundamental o conhecimento da bioquímica e fisiologia dos microrganismos envolvidos. Assim, este estudo tem o objetivo de obter informações bioquímicas de leveduras industriais, principalmente ao que se refere à hidrólise da sacarose e maltose pela enzima invertase (β-frutofuranosidase, EC 3.2.1.26) e maltase (α- glicosidase, EC 3.2.1.20) respectivamente. As linhagens industriais Ethanol RedTM (Fermentis/Lasaffre - linhagem francesa) PE-2, SA-1, CAT-1 e BG (linhagens brasileiras) foram cultivadas em meios contendo diferentes fontes de carbono (sacarose, glicose, frutose, maltose e galactose), suplementados com peptona e extrato de levedo, e avaliadas com relação a produção de biomassa, consumo da fonte de carbono, viabilidade celular e níveis de atividade invertásica e maltásica. Resultados mostraram que todas as linhagens apresentam crescimento rápido e intenso em sacarose, glicose e frutose, porém apresentam comportamento diferente em meios contendo maltose e galactose. Todas as linhagens crescem lentamente em galactose. Ethanol RedTM é mais adaptada para o crescimento em maltose do que as linhagens brasileiras PE-2 e SA-1. As outras linhagens brasileiras (CAT-1 e BG) não crescem em maltose devido à ausência de atividade maltásica. Com relação aos níveis de atividade invertásica, foi identificada a presença de três categorias de linhagens: uma com altos níveis de atividade (Ethanol RedTM), outra com níveis mais baixos (PE-2, CAT-1), e uma terceira categoria com atividade intermediária entre estas duas primeiras categorias (SA-1 e BG). Além do valor acadêmico, os resultados obtidos têm importância aplicada na medida em que indicam que as linhagens industriais produtoras de etanol combustível apresentam diferentes características fisiológicas, que podem ser exploradas para aperfeiçoar o processo de fermentação alcoólica / For the improvement of the industrial ethanol fuel-producing process, it is crucial to understand the biochemistry and physiology of the microorganisms involved. This study aims to obtain biochemical information of industrial yeasts, especially when it refers to the hydrolysis of sucrose and maltose by the enzyme invertase (β-frutofuranosidase, EC 3.2.1.26) and maltase (α-glicosidase, EC 3.2.1.20) respectively. The industrial strains Ethanol RedTM (Fermentis/Lasaffre - French strain) PE-2, SA-1, CAT-1 and BG (Brazilian strains) were cultured in media containing different carbon sources (sucrose, glucose, fructose, maltose and galactose) supplemented with peptone and yeast extract, and evaluated relative to biomass production, carbon source consumption, cell viability and levels of invertase and maltase activities. Results showed that all strains exhibit rapid and intense growth in presence of sucrose, glucose and fructose, but they have differing behavior in media containing maltose and galactose. All strains grow slowly on galactose. Ethanol RedTM is more adapted for growing in maltose than Brazilian PE-2 and CAT- 1. The remaining Brazilian strains (BG and CAT-1) do not grow in maltose, due to the absence of maltase activity. As far as the levels of invertase activity is concerned, three categories of strains have been identified: with high activity levels (Ethanol RedTM), with lower levels (PE-2, CAT-1), and a third category with intermediate activity levels between these first two categories (SA-1 and BG). Besides academic value, the results obtained have applied significance in indicating that industrial ethanol fuel-producing strains exhibit different physiological characteristics that can be exploited to improve the fermentation process

Resumo: O ácido lático é produzido preferencialmente durante o metabolismo fermentativo de carboidratos por bactérias láticas (BAL). Esse processo metabólico anaeróbio gera 2 moles de ácido lático partindo-se de 1 mol de glicose. Procurando-se obtenção de ácido em meios de cultivo de baixo custo, foram avaliados 3 meios de cultivo: CSN a base de caldo de canade- açúcar, MRS modificado (2% de glicose) e o meio Padrão (4% sacarose). Para cada meio utilizou-se 4 Erlenmeyer's de 250 mL sendo 1 deles o controle e os demais contendo as bactérias. Empregou-se após seleção prévia Lactobacillus delbrueckii 103.10.2 e linhagem selvagem não identificada na condição estática (30 ± 2°C) e agitada (150 rpm, temperatura de 30 ± 2°C) por 72 h. Os meios foram enriquecidos com extrato de tomate em diferentes concentrações (0; 0,5 ; 2 e 4%). O ácido lático produzido foi quantificado enzimaticamente pelo Accutrend Lactate® e a acidez total por titulometria. Acompanhou-se o consumo da glicose pelo método do ADNS. Verificou-se que 34,35gL-1 de ácido lático foram obtidos em 72 h de fermentação agitada pela linhagem selvagem não identificada, no meio CSN 12 brix acrescido de 4% de extrato de tomate, sendo consumidos 16,1 gL-1 de glicose. A linhagem Lactobacillus delbrueckii 103.10.2 produziu 27,90gL-1 de ácido lático em meio Padrão, contendo 0,5% de extrato de tomate, durante as 72h de cultivo. / Abstract: The lactic acid is produced preferably during fermentative metabolism of carbohydrate for lactic acid bacteria (BAL). In this anaerobic metabolic process, two lactic acid molecules are produced from each molecule of glucose. In this study Lactobacillus delbrueckii 103.10.2 and unidentified wild strain was assayed in three different culture media: modified MRS medium (2% glucose), CSN (sugar-cane juice supplemented with nutrients) and a standard medium (4% sucrose) with agitation or under stationary conditions, enriched with tomato extract (0; 0,5 ; 2 and 4%). The lactic acid produced was measured with the Accutrend Lactate® as well as titration method (verification of acidity); and glucose concentration was determined by ADNS method. The best strain for lactic acid production was unidentified wild strain, presenting 34,35 gL-1 of lactic acid in the CSN 12 brix medium enriched with 4% of tomato extract; 16,1 gL-1 of glucose was consumed, at 30 ± 2°C for 72h, under agitation at 150 rpm. / Orientador: Dejanira de Franceschi de Angelis / Coorientador: Jonas Contiero / Banca: Marta Cristina Teixeira Duarte / Banca: Octavio Antonio Valsechi / Mestre

Orientador: Maria Isabel Rodrigues / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-06T16:00:21Z (GMT). No. of bitstreams: 1 Mendes_GuilhermeLopes_M.pdf: 1683620 bytes, checksum: 61fa8e0621ddee5d8253c384bb74286f (MD5) Previous issue date: 2006 / Mestrado / Mestre em Engenharia de Alimentos