Effect of different starvation conditions on the flocculation of Saccharomyces cerevisiae |
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Authors: | Soares E V Vroman A |
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Institution: | CIEA - Departamento de Engenharia Química, Instituto Superior de Engenharia do Instituto Politécnico do Porto, Rua Dr António Bernardino de Almeida, Porto, Portugal. evs@isep.ipp.pt |
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Abstract: | AIMS: To study the effect of different starvation conditions on the flocculation of an ale brewing yeast of Saccharomyces cerevisiae NCYC 1195. METHODS AND RESULTS: Flocculation was assessed by a micro-flocculation technique (Soares and Mota 1997). Carbon-starved cells of a NewFlo phenotype strain did not lose flocculation during a 48 h period. Cells incubated only in the presence of fermentable carbon sources (glucose, galactose and maltose at 2%, w/v), showed a progressive flocculation loss. The incubation of cells in 4% (v/v) ethanol did not induce a flocculation loss. The simultaneous incubation of cells in the presence of 2% (w/v) glucose and 15 microg ml(-1) cycloheximide hindered flocculation loss. The presence of 0.1 mmol l(-1) PMSF or 10 mmol l-1 EDTA prevented partially or completely, respectively, the loss of flocculation in the presence of glucose. CONCLUSIONS: Fermentable sugars induced a flocculation loss, which seems to require de novo protein synthesis and the involvement of different proteases. SIGNIFICANCE AND IMPACT OF THE STUDY: The findings reported here contribute to the elucidation of the role of nutrients on the physiological control of yeast flocculation. |
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Keywords: | brewer's yeast carbon source flocculation Flo1 phenotype NewFlo phenotype proteases protein synthesis starvation |
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