title: The effect of oxygen on the survival of non-Saccharomyces yeasts during mixed culture fermentations of grape juice with Saccharomyces cerevisiae.
abstract: OBJECTIVE
  The effect of oxygen on the survival of Torulaspora delbrueckii and Kluyveromyces thermotolerans during mixed culture fermentations in grape juice with Saccharomyces cerevisiae was investigated.
  
  
  RESULTS
  Fermentations were carried out in two simple fermentation systems differing in the availability of oxygen. At low available oxygen conditions, T. delbrueckii and K. thermotolerans began to die off after two days of mixed culture fermentation. In filtrates from 2-day-old mixed cultures, single cultures of T. delbrueckii and K. thermotolerans survived and actively produced ethanol to concentrations of approx. 65 and 70 g l-1, respectively, at low available oxygen conditions. Oxygen clearly increased the survival time and decreased the death rate of T. delbrueckii and K. thermotolerans in mixed cultures, whereas it did not affect the growth and survival of S. cerevisiae.
  
  
  CONCLUSIONS
  Our results show that the deaths of T. delbrueckii and K. thermotolerans in mixed cultures at low available oxygen conditions are not due to toxic metabolites produced by the yeasts but rather to the lack of oxygen. Furthermore, they indicate that T. delbrueckii and K. thermotolerans are less tolerant to low available oxygen conditions than S. cerevisiae.
  
  
  CONCLUSIONS
  Our study reveals new knowledge on the mechanisms underlying the succession of yeasts during wine fermentations. This knowledge may be of importance when creating defined, mixed starter cultures for the controlled production of wines with a wide range of flavour compositions.
authors.affiliation: Department of Dairy and Food Science, The Royal Veterinary and Agricultural University, Frederiksberg C, Denmark.
authors.forename: E
authors.initials: E
authors.lastname: Holm Hansen
authors.forename: P
authors.initials: P
authors.lastname: Nissen
authors.forename: P
authors.initials: P
authors.lastname: Sommer
authors.forename: J C
authors.initials: JC
authors.lastname: Nielsen
authors.forename: N
authors.initials: N
authors.lastname: Arneborg
mesh_terms: D050260:Carbohydrate Metabolism; D018929:Cell Culture Techniques; D002455:Cell Division; D018920:Coculture Techniques; D000431:Ethanol / Q000378:metabolism; D005285:Fermentation; D007716:Kluyveromyces / Q000166:cytology / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000378:metabolism*; D013997:Time Factors; D027843:Vitis / Q000378:metabolism* / Q000382:microbiology*; D014920:Wine / Q000382:microbiology; D015003:Yeasts / Q000166:cytology* / Q000378:metabolism*
chemical_list: D000431:Ethanol; D010100:Oxygen