Orientador : Salvador Massagner Roig

Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos

Resumo: Foram estudadas as leveduras Saccharomyces fragilis ATCC 8612, Saccharomyces fragilis ATCC 8635, Saccharomyces fragilis ATCC 16045, Saccharomyces fragilis ATCC 100220, Saccharomyces fragilis NRRL Y-2415, Candida pseudotropicalis ATCC 8659 e Candida pseudotropicalis IOC 2697, com o objetivo...

Resumo: Foram estudadas as leveduras Saccharomyces fragilis ATCC 8612, Saccharomyces fragilis ATCC 8635, Saccharomyces fragilis ATCC 16045, Saccharomyces fragilis ATCC 100220, Saccharomyces fragilis NRRL Y-2415, Candida pseudotropicalis ATCC 8659 e Candida pseudotropicalis IOC 2697, com o objetivo de- selecionar aquela que apre¬sentasse o melhor desempenho em metabolizar lactose e produzir ß-galactosidase. Das leveduras ensaiadas seis demonstraram ser hábeis para fermentar lactose em meio sintético, com exceção da Candida pseudotropicalis IOC 2697, que utiliza lactose de forma muito lenta. Houve necessidade de controlar o pH da- fermentação de meio sintético, uma vez que ocorreu a produuço de cidos pelas leveduras, o que causou diminuiiço do pH ate a inibiiço das mesmas. A fermentaaço de permeado de soro de queijo concentrado a 22,5% de lactose, apps a adaptaaço das leveduras, mostrou que a Saccharomyces fragilis NRRL Y-2415 foi a levedura que mais consumiu lactose, chegando a produzir cerca de 47 g/l, de etanol. A Saccharomyces fragilis NRRL Y-2415 consumiu toda a lacctose do permeado quando a concentraaço inicial desta era de 10%, sendo que o consumo total da lactose do permeado concentrado a 15% de lactose tambbm foi posssvel quando a cultura foi aerada na sua fase inicial, com uma produuço de cerca de 57g/l de etanol. Da auttlise das cclulas de Saccharomyces fragilis NRRL Y-2415, obtidas da fermentaaço de permeado com 15% de lactose e aeraaço na fase iniciai, resultou um extrato de -galactosidase. Paara o menor tempo de auttlise (17 horas) obteve-se uma atividade de cerca de 41,98 mol de glicose liberada por miligrama de cclulas autolisadas e por minuto, quando testada em soluuço 5% de lactose. A medida em que o tempo de auttlise aumentou, aumentou tambbm o nnmero de cclulas rompidas, bem como a atividade de lactose medida em mol de glicose liberada por mililitro de extrato enzimmtico. Conntudo, a atividade medida em mol de glicose liberada por miligrama de cclulas autolisadas e por minuto diminuiu. Esta enzima quando testada em soluuçes de lactose, apreesentou um Km mmdio de 60,32 mM de lactose.

Abstract: The following yeasts: Saccharomyces fragilis ATCC 8612, Saccharomyces fragilis ATCC 8635, Saccharomyces fragilis ATCC 16045, Saccharomyces fragilis ATCC 100220, Saccharomyces fragilis NRRL Y-2415, Candida pseudotropicalis ATCC 8659 and Candida pseudotropicalis IOC 2697 were studied with...

Abstract: The following yeasts: Saccharomyces fragilis ATCC 8612, Saccharomyces fragilis ATCC 8635, Saccharomyces fragilis ATCC 16045, Saccharomyces fragilis ATCC 100220, Saccharomyces fragilis NRRL Y-2415, Candida pseudotropicalis ATCC 8659 and Candida pseudotropicalis IOC 2697 were studied with the objective of to select the best lactose fermentative as well lactase producer. From these yeasts six demonstrated to be able to ferment lactose in sintetic media, with exception of Candida pseudotropicalis IOC 2697 which is a slow lactose metabilizer. It was necessary to control the pH on the sintetic media fermentation since there was acid production by the yeasts which caused the pH decrease and the yeasts inhibition. Saccharomyces fragilis NRRL Y-2415 showed to be the best lactose metabolizer on the fermentation of cheese whey permeate concentrated at 22.5% lactose, producing up to 47g/l of ethanol. Saccharomyces fragilis NRRL Y-2415 consumed all the lactose present on the whey permeate when the initial concentration was 10%, The total consumption of lactose also was possible with 15% lactose whey permeate when the culture was aerated on the initial phase obtaining up to 57g /l ethanol. A ß-galactosidase extract was obtained from the autolised cells of Saccharomyces fragilis NRRL Y-2415 obtained from fermentation of 15% lactose whey permeat with aeration on the initial phase. For the lowest autolisis time (17 hours) it was obtained an approximated activity of 41.98 µmol of glucose liberated per miligram of autolised cells-minute, when it was tested in a 5% lactose solution. The increase of autolisis time resulted in an increase on disrupted cells as well as in an increase of lactose activity expressed in µmol liberated glucose per millimeter of enzymatic extract, however the enzymatic activity expressed as µrnol of liberated glucose per milligram of autolised cells-minute decreased. This enzyme when tested on lactose solution presented an average Km of 60.32mM of lactose.