Carbohydrate carbon sources induce loss of flocculation of an ale-brewing yeast strain.
OBJECTIVE
To identify the nutrients that can trigger the loss of flocculation under growth conditions in an ale-brewing strain, Saccharomyces cerevisiae NCYC 1195.


RESULTS
Flocculation was evaluated using the method of Soares, E.V. and Vroman, A. [Journal of Applied Microbiology (2003) 95, 325]. Yeast growth with metabolizable carbon sources (glucose, fructose, galactose, maltose or sucrose) at 2% (w/v), induced the loss of flocculation in yeast that had previously been allowed to flocculate. The yeast remained flocculent when transferred to a medium containing the required nutrients for yeast growth and a sole nonmetabolizable carbon source (lactose). Transfer of flocculent yeast into a growth medium with ethanol (4% v/v), as the sole carbon source did not induce the loss of flocculation. Even the addition of glucose (2% w/v) or glucose and antimycin A (0.1 mg l(-1)) to this culture did not bring about loss of flocculation. Cycloheximide addition (15 mg l(-1)) to glucose-growing cells stopped flocculation loss.


CONCLUSIONS
Carbohydrates were the nutrients responsible for stimulating the loss of flocculation in flocculent yeast cells transferred to growing conditions. The glucose-induced loss of flocculation required de novo protein synthesis. Ethanol prevented glucose-induced loss of flocculation. This protective effect of ethanol was independent of the respiratory function of the yeast.


CONCLUSIONS
This work contributes to the elucidation of the role of nutrients in the control of the flocculation cycle in NewFlo phenotype yeast strains.
Soares
E V
EV
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
Vroman
A
A
Mortier
J
J
Rijsbrack
K
K
Mota
M
M
D000935:Antifungal Agents / Q000494:pharmacology; D000968:Antimycin A / Q000494:pharmacology; D050260:Carbohydrate Metabolism; D002244:Carbon / Q000378:metabolism*; D003470:Culture Media; D003513:Cycloheximide / Q000494:pharmacology; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation / Q000502:physiology; D005427:Flocculation; D005632:Fructose / Q000378:metabolism; D005690:Galactose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D007785:Lactose / Q000378:metabolism; D008320:Maltose / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis; D013395:Sucrose / Q000378:metabolism
D000935:Antifungal Agents; D003470:Culture Media; D029701:Saccharomyces cerevisiae Proteins; D005632:Fructose; D000431:Ethanol; D013395:Sucrose; D000968:Antimycin A; D008320:Maltose; D002244:Carbon; D003513:Cycloheximide; D005947:Glucose; D007785:Lactose; D005690:Galactose