Kluyveromyces thermotolerans

Genus/speciesKluyveromyces thermotolerans  (Candida dattila anamorph;Cryptococcus dattila, Kluyveromyces veronae, Saccharomyces thermotolerans, Saccharomyces veronae, Torulopsis dattila, Zygosaccharomyces thermotolerans)

 

Classification: Ascomycete, teleomorph

Morphology:

  • Cell: mulitlateral budding; spheroidal to ellipsoidal, occur singly in pairs or short chains or small clusters; simple to complex pseudohyphae may form.
  • Colony: cream-colored to brownish cream, shiny to dull, forms smooth, white, slightly shiny colonies.
  • Malt agar: growth on malt agar also forms smooth, cream colored, slightly shiny colonies.
  • WL: Kluyveromyces thermotolerans is not sensitive to acitdione and will grow on WL plates.
  • Spore: one to four spheriodal spores containing lipid globules.
  • Zygote: conjugation immediately precedes ascus formation.
  • Ascus: evanescent asci.
  • Liquid Growth: Sediment and/or ring may be formed.

 

Physiological Traits:

  • Fermentation: Glucose, Sucrose, Raffinose
  • Assimilation: Galactose, Sucrose, Sorbose, Maltose, Trehalose, Raffinose, Melezitose, Glycerol, Ethanol; Variable: Mannitol, Inulin, Succinate, Gluconate, Glucitol, Xylitol, Ribitol; No assimilation of nitrate or nitrite; Use of ethylamine as sole N source; variable use of lysine, cadaverine and tryptophan as sole N source; No growth in vitamin-free medium, requires inositol, thiamin.
  • Growth: 37 C: variable
  • Growth Sensitivities: variable growth on 10 and 16% NaCl; growth on high glucose concentrations; not tolerant of cycloheximide
  • Chromosome bands: 4 reported
  • Kluyveromyces thermotolerans utilizes grapes sugars as substrates and produces ethanol.  Kluyveromyces thermotolerans is also known to produce lactic acid in fermentation.

Ecological Traits:

This microbe is often found on fruits in nature, specifically it is often present on the surfaces of grapes.

Distinguishing Features:

Growth in the presence of high osmolarity

Role in wine:

This organism is considered a normal grape and fermentation flora that is often found at the beginning of many fermentations before Saccharomyces dominates the fermentation.  Wine produced by fermentation by Kluyveromyces thermotolerans is considered to have some different sensory properties, such as different mouth feel due to production of lactic acid.  Some winemakers may desire these resulting traits in their wines. Kluyveromyces thermotolerans is present in some commercial yeast inoculates.

Sensitivities:

  • SO2: This organism has been found to be only slightly sensitive to SO2
  • Sorbate­­­­­:
  • DMDC: Is sensitive to DMDC
  • pH: Is sensitive to very low pH levels
  • Acids:
  • Ethanol: is sensitive to ethanol.  This is why Saccharomyces frequently dominates the end of fermentations started byKluyveromyces thermotolerans.
  • Anaerobiosis: Requires oxygen to utilize some substrates
  • Heat:

References:

  • Boulton, R.B., Singleton,. V., Bisson, L., and Kunkee, R., Principles and Practices of Winemaking. 1996 Chapman & Hall, New York.
  • Kujumdzieva, A., Nedeva, T., Morfova, M., and Savov, V., 1998 Isolation and Characterisation of Two Thermotolerant Kluyveromyces Yeast  Strains.  Journal of Culture Collections 2:44-50.