Schizosaccharomyces pombe yeast and its role in winemaking

by | Nov 1, 2020 | Oenology research, Winetech Technical

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Current and previous names

Schizosaccharomyces pombe has previously been designated several species names based on classical yeast taxonomy methods; amongst its synonyms are S. vordermani, S. mellacei, S. fermosensis, S. santawensis, S. pinan, S. taito, S. liquefaciens, S. acidovorans, S. malidevorans and S. kambucha.1 However, these synonyms became obsolete once the genus was reduced to three species following reclassification based on molecular DNA-based techniques.

Where it is found

Schizosaccharomyces pombe strains have been isolated from fermented drinks or derived products (grapes, must, wine, beer and kombucha tea) and in high sugar substrates, such as honey, sweets, molasses and dried fruit.2,3

What it looks like

Schizosaccharomyces pombe is known as the fission yeast due to its peculiar asexual reproduction by binary fission rather than budding which is common among yeasts. It forms rod-shaped cells varying between 3 – 5 x 5 – 24 µm commonly appearing as single cells or in pairs.2,3 Sexual reproduction results in the formation of two to four haploid ascospores.

Nitrogen metabolism

Schizosaccharomyces pombe has low nitrogen requirement. Strains of this species show preferential consumption of ammonia over primary amino nitrogen. Moreover, compared to Saccharomyces species, this yeast displayed lower growth rates and minimal requirements for primary amino nitrogen.4

Technical characteristics

Schizosaccharomyces pombe is an osmotolerant yeast capable of growth in the presence of 500 g/L glucose. It ferments optimally at temperatures between 24 and 30°C. It is a facultative anaerobe and possesses a high fermentative power similar to Saccharomyces cerevisiae, producing 11 – 13% alcohol in anaerobic conditions and 14 – 15% with slight aeration.2 Schizosaccharomyces pombe is more resistant to SO2 than most S. cerevisiae strains. It can remain active at SO2 levels up to 300 ppm which is approximately 148 ppm free SO2.5

  • Glycerol, VA, SO2 and H2S production

Schizosaccharomyces pombe can ferment to dryness in monoculture. However, the fermentations are typically slow and generate excessive amounts of acetic acid. Most strains produce more than 1 g/L of volatile acidity.6 This yeast has also been characterised as a high H2S producer compared to S. cerevisiae and produces on average 1 g higher glycerol than S. cerevisiae. Some strains of S. pombe were shown to produce up to 10 g/L glycerol in synthetic grape juice with 222 g/L (glucose + fructose) initial sugar concentration.6 Only 5% of the studied strains present an appropriate industrial profile, based on classic parameters, such as correct sugar consumption, moderate acetic acid production, complete malic acid degradation, glycerol production, and the correct sensory profile of the wines produced with these strains.2

  • Mixed culture fermentations

Schizosaccharomyces pombe has been evaluated for its use in co-fermentation with S. cerevisiae, as well as other non-Saccharomyces yeasts, such as Lachancea thermotolerans and Torulaspora delbrueckii. The combined use of S. pombe with strains of these species has been shown to moderate its undesirable and quality-detrimental vinegar character.7

Effect on malolactic fermentation

Schizosaccharomyces pombe has a high capacity to metabolise malic acid into ethanol and CO2 during anaerobic fermentation processes. Consequently, it has been used to reduce acidity in wines presenting high levels of malic acid.

Traits of oenological interest

Generally, S. pombe is reported to produce significantly lower concentrations of higher alcohols and esters than S. cerevisiae and other yeast species.7 However, it is considered as a desirable yeast for modulating other wine organoleptic characteristics and wine quality. Amongst its positive attributes are the control of biogenic amines as no bacterial malolactic fermentation is required, and the reduction of gluconic acid in wines derived from rotten grapes.2

  • Extracellular enzymes

Schizosaccharomyces pombe produces high levels of urease. This enzyme hydrolyses urea which is a precursor ethyl carbamate, a carcinogen.8

  • Mannoprotein content – effects on wine stability

Schizosaccharomyces pombe has high autolytic release of cell wall polysaccharides which makes it desirable for aging over lees. Its most prominent polysaccharides are α-galactomannose and β-glucans.2,7

  • Pyruvic acid content – effects on wine colour

Schizosaccharomyces pombe displays elevated production of pyruvic acid producing up to five times more pyruvic acid than S. cerevisiae depending on the strain.7 The high pyruvic acid facilitates the formation of stable vitisin A-type derivatives (and some strains, also vinyl phenolic pyroanthocyanins, which are less sensitive to SO2 bleaching) by chemical condensation with grape anthocyanins.9

Conclusion

Schizosaccharomyces pombe is the most recommended non-Saccharomyces species to de-acidify excessively acidic wines from cool areas, such as those from the north of Europe.7 However, this has not spurred the development of commercial strains. Currently, only S. pombe Promalic (www.aeb-group.com/en/promalic-oenology-4903) is available on the market.

References

  1. Vaughan-Martini, A. & Martini, A., 2011. Schizosaccharomyces Lindner (1893). Kurtzman, C., Fell, J.W. & Boekhout, T. (eds). The Yeasts (5th Edition), p 779 – 784. Elsevier Science.
  2. Benito, A., Calderón, F. & Benito, S., 2016. New trends in Schizosaccharomyces use for winemaking. Morata, A. & Loira, I. (eds). Grape and Wine Biotechnology, Chapter 14. IntechOpen.
  3. Loira, I., Morata, A., Palomero, F., González C. & Suárez-Lepe, A., 2018. Schizosaccharomyces pombe: A promising biotechnology for modulating wine composition. Fermentation 4, 70.
  4. Benito, S., Palomero, F., Morata, A., Calderón F. & Suárez-Lepe, J.A., 2012. New applications for Schizosaccharomyces pombe in the alcoholic fermentation of red wines. International Journal of Food Science and Technology 47, 2101 – 2108.
  5. Yang, H.Y., 1975. Effect of sulfur dioxide on the activity of Schizosaccharomyces pombe. American Journal of Enology and Viticulture 26(1), 1 – 4.
  6. Benito, S., Palomero, F., Calderón, F., Plamero, D. & Suárez-Lepe, J.A., 2014. Selection of appropriate Schizosaccharomyces strains for winemaking. Food Microbiology 42, 218 – 224.
  7. Benito, A., Calderón, F. & Benito, S., 2019. The influence of non-Saccharomyces species on wine fermentation quality parameters. Fermentation 5, 54.
  8. Vejarano, R., 2020. Non-Saccharomyces in winemaking: Source of mannoproteins, nitrogen, enzymes and antimicrobial compounds. Fermentation 6, 76.
  9. Morata, A., Escott, C., Bañuelos, A., Loira, I., De Fresno, J.M., González, C. & Suárez-Lepe, J.A., 2020. Contribution of non-Saccharomyces yeasts to wine freshness – a review. Biomolecules 10, 34.

– For more information, contact Evodia Setati at setati@sun.ac.za.

 

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