Genus/species (aliases): Saccharomyces exiguous (Candida holmii, anamorph, Cryptococcus holmii, Torula homii, Torulaspora exigua, Torulopsis alactosa, Torulopsis holmii)
Classification: Ascomycete, teleomorph
Morphology:
Cell: reproduce by budding, spherical to ovoid or elongate, often arranged in pairs
Colony: Malt agar: white to cream-colored, shiny and smooth
Reproduction:
- Spore: smooth oval or spherical spores
- Zygote:
- Ascus: spherical, one to four ascospores, asci persistent
Liquid Growth: non-flocculent, no pellicle formation, no ring growth.
Physiological Traits:
- Fermentation: Glucose, Galactose, Sucrose, Trehalose; variable: Raffinose
- Assimilation: Galactose, Sucrose, Trehalose variable: Raffinose, Lactate, Succinate, Ethanol; No assimilation of nitrate or nitrite; no use of ethylamine, lysine or cadaverine as sole N source; No growth in vitamin-free medium, requires biotin and/or thiamin and/or pantothenate
- Growth 37 C: negative
- Growth Sensitivities: resistant to low (0.01%) cycloheximide; some strains resistant to 10% NaCl
- Chromosome bands: 2 to 16 described
Ecological Traits: A wild yeast found on plants, fruits and grains.
Distinguishing Features:
Produces acid, uses NH4 2SO4 as primary source of Nitrogen.
Role in wine:
Has been reported in wine, but occurrence is rare.
Sensitivities:
- SO2:
- Sorbate:
- DMDC:
- pH: Unknown
- Acid high tolerance
- Ethanol low tolerance
- Anaerobiosis aerobic and semi-aerobic only
- Heat 11C – 33C is tolerable range, 28C optimum
References:
Brocklehurst, T.F., White, C.A. & Dennis, C. The microflora of stored coleslaw and factors affecting the growth of spoilage yeasts in coleslaw. Journal of Applied Bacteriology, 55, 57-63.