title: Fine measurement of ergosterol requirements for growth of Saccharomyces cerevisiae during alcoholic fermentation.
abstract: Yeasts can incorporate a wide variety of exogenous sterols under strict anaerobiosis. Yeasts normally require oxygen for growth when exogenous sterols are limiting, as this favours the synthesis of lipids (sterols and unsaturated fatty acids). Although much is known about the oxygen requirements of yeasts during anaerobic growth, little is known about their exact sterol requirements in such conditions. We developed a method to determine the amount of ergosterol required for the growth of several yeast strains. We found that pre-cultured yeast strains all contained similar amounts of stored sterols, but exhibited different ergosterol assimilation efficiencies in enological conditions [as measured by the ergosterol concentration required to sustain half the number of generations attributed to ergosterol assimilation (P(50))]. P(50) was correlated with the intensity of sterol synthesis. Active dry yeasts (ADYs) contained less stored sterols than their pre-cultured counterparts and displayed very different ergosterol assimilation efficiencies. We showed that five different batches of the same industrial Saccharomyces cerevisiae ADY exhibited significantly different ergosterol requirements for growth. These differences were mainly attributed to differences in initial sterol reserves. The method described here can therefore be used to quantify indirectly the sterol synthesis abilities of yeast strains and to estimate the size of sterol reserves.
authors.affiliation: Equipe Microbiologie et de Technologie des Fermentations, UMR 1083 Sciences pour l'Oenologie, Institut National de la Recherche Agronomique, 34060 Montpellier Cedex 1, France.
authors.forename: Christelle
authors.initials: C
authors.lastname: Deytieux
authors.forename: Ludivine
authors.initials: L
authors.lastname: Mussard
authors.forename: Marie-José
authors.initials: MJ
authors.lastname: Biron
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Salmon
mesh_terms: D000438:Alcohols / Q000378:metabolism*; D000693:Anaerobiosis; D001681:Biological Assay / Q000379:methods*; D003470:Culture Media; D004875:Ergosterol / Q000032:analysis* / Q000378:metabolism; D005285:Fermentation; D012441:Saccharomyces cerevisiae / Q000254:growth & development / Q000378:metabolism*
chemical_list: D000438:Alcohols; D003470:Culture Media; D004875:Ergosterol