Instituto Politécnico do Porto. Fundo de Apoio à Investigação, Programa Plurianual de Unidades de I&D - CIEA/ISEP

Duarte, Abel A.

Mota, M.

Soares, Eduardo V.

Universidade do Minho: RepositoriUM

BIOTEC’98 APM007 151 Effect of the Carbon Source in the Regulation of Flocculation of Ale Brewer Yeast Strains  Eduardo V. Soares1*, Abel A. Duarte2 and Manuel Mota3 1CIEA, Departamento de Engenharia Química, Instituto Superior de Engenharia do Instituto Politécnico do Porto, Rua de S. Tomé, 4200 Porto, Portugal 2CIEA, Instituto Superior de Engenharia do Instituto Politécnico do Porto, Rua de S. Tomé, 4200 Porto, Portugal 3Centro de Engenharia Biológica - IBQF, Universidade do Minho, 4700 Braga, Portugal  Key words: Saccharomyces cerevisiae, flocculation inhibition, carbon metabolism, growth media   Yeast flocculation has been used in many fermentation processes, being traditionally exploited in the brewing industry. The ideal brewing yeast grows as discrete cells and flocculate after sugar depletion from the media, leaving clear beer[1].  Despite the commercial importance of yeast flocculation, little is known about the regulation of this characteristic. In a previous work[2], it was found that a high flocculent ale brewer strain, when transferred to fresh rich medium with glucose, was induced to growth and progressively loss its flocculation ability.  In the present work, the loss of flocculation of three ale brewer strains (NCYC 1195, NCYC 1214 and NCYC 1364), was investigated. These strains were cultured in defined medium, with the principal sugars (except maltotriose), found in the worth: glucose, fructose, sucrose and maltose. Our studies showed that all sugars tested were able to induce the loss of flocculation of the strains. In the present communication, the different hypothesis to explain the loss of flocculation in the beginning of growth of the ale yeast brewer strains, are discussed.  [1] Stewart, G.G. and Russell, I. Brewing Science, Vol 2, Edited by J. R. Pollock. Academic Press, London, pp. 61-92, 1981. [2] Soares, E.V. and Mota, M. Can. J. Microbiol., 42, 539 - 547, 1996.  This work was supported by Fundo de Apoio à Investigação from Instituto Politécnico do Porto (Project P 24/97) and by Programa Plurianual de Unidades de I&D - CIEA/ISEP.  Abel A. Duarte was financially supported by a grant from Programa Praxis XXI/BTI/12001/97. 

Effect of the carbon source in the regulation of flocculation of Ale Brewer yeast strains

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Effect of the carbon source in the regulation of flocculation of Ale Brewer yeast strains

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Universidade do Minho: RepositoriUM