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The effect of the addition of proteases and glucanases during yeast autolysis on the production and properties of yeast extracts

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Yeast extracts (YE) were produced with the addition of proteases or glucanases during bakers' yeast (Saccharomyces cerevisiae) autolysis. Chemical composition, physical properties, and biological value of the YE were examined. Proteases had the highest impact on the turbidity and filterability of YE. All 11 proteases and two glucanases increased YE yields (% yeast solids solubilized) obtained from heated (80°C/15 min) bakers' yeast creams (BYC). However, when proteases were added to native (unheated) BYC during autolysis, few increased YE yields, with papain being the most effective. The increased yields were generally related to increased levels of total nitrogen (TN) and α-amino nitrogen (α-AN) in the YE. Media were supplemented with the various yeast extracts, and the highest growth rates (µmax) and biomass values (ODmax) of Lactobacillus acidophilus were noted. The best growth was obtained with YE produced with native BYC treated with a fungal protease, and results of this study show that some enzymes could be used to produce improved YE for microbiological media.Key words: turbidity, filtration, amino acids, Lactobacillus.

Des extraits de levure (EL) furent produits avec l'addition de protéases et de glucanases lors de l'autolyse de levures de boulangerie (Saccharomyces cerevisiae). La composition chimique, les propriétés physiques et la valeur biologique des EL furent examinés. Les protéases eurent l'impact le plus marqué sur la facilité de filtration des EL obtenus. Les 11 protéases et glucanases ont accru les rendements d'EL obtenus de crèmes de levures préalablement chauffées à 80°C pendant 15 min. Toutefois, lorsque les enzymes étaient ajoutées à des suspensions de levures fraîches (non chauffées) durant l'incubation, peu d'enzymes accrurent les rendements d'autolyse, et la papaïne fut la plus efficace à cet effet. L'augmentation des rendements était associée à une augmentation en azote totale (AT) dans les EL. Les protéases influencèrent aussi la teneur en azote α-aminé (AαA) et les rapports AT-AαA. Les EL produits furent ajoutés à un milieu minimal, et les taux de croissance les plus élevés (µmax) ainsi que les biomasses les plus importantes (ODmax) de Lactobacillus acidophilus furent examinés. La croissance la plus poussée fut obtenue avec un EL produit avec des cultures fraîches incubées en présence d'un protéase d'origine fongique et les résultats de cette étude suggèrent que des enzymes pourraient être ajoutées lors de l'autolyse des levures afin d'en modifier les propriétés bio-stimulantes pour les milieux de culture.Mots clés : turbidité, filtration, acides amino, Lactobacillus.

Keywords: Lactobacillus; acides amino; amino acids; filtration; turbidity; turbidité

Document Type: Research Article

Publication date: 2001-01-01

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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