Torulaspora delbrueckii and its role in winemaking

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Torulaspora delbrueckii is generally regarded as a low producer of aroma compounds, in particular higher alcohols and esters, however, this is strain dependent.

Current and previous names

Torulaspora delbrueckii has had many synonyms, amongst them Saccharomyces rosei or Saccharomyces roseus and Saccharomyces delbrueckii. Its anamorph is Candida colliculosa.

Where it is found

Torulaspora delbrueckii is ubiquitous and has been frequently isolated from natural environments (plants, soil and insects) and from various habitats associated with human activities, such as winemaking, kefir, mezcal, colonche, olive, and tequila and cider production. Strains associated with grapes and wine form a genetically distinct group from those derived from other bioprocesses.¹

What it looks like

Torulaspora delbrueckii forms spherical to ellipsoidal cells which are 2 – 5 x 3 – 7 µm in size, slightly smaller than S. cerevisiae. On Wallerstein nutrient agar, the colonies of T. delbrueckii are knoblike with a smooth surface and a cream to light green pigmentation similar to S. cerevisiae.² Torulaspora delbrueckii reproduces asexually by multilateral budding and sexually with the formation of up to four spherical ascospores.³

Technical characteristics

Torulaspora delbrueckii is a moderate fermenter with less fermentation vigour and slower growth rate than S. cerevisiae. Most strains cannot ferment to dryness and produce varying amounts of ethanol ranging from 5 – 11% (v/v) and can tolerate up to 10% ethanol and ferment to dryness in 50 mg/L SO₂. A sequential inoculation with S. cerevisiae at a ratio of 10:1 (i.e. 10⁷ cells/mL T. delbrueckii: 10⁶ cells/mL S. cerevisiae) is recommended to allow significant contribution of T. delbrueckii.^4-6 Torulaspora delbrueckii establishes better in clarified juice, which has less diversity and density of wild yeasts than unclarified must.

Nitrogen metabolism

Torulaspora delbrueckii displays similar nitrogen consumption and nitrogen source influence profile to S. cerevisiae.^7,8 Most importantly, production of acetic acid in the yeast is influenced by the nitrogen composition with NH₄⁺ resulting in the lowest acetic acid production compared to media with a mix of NH₄⁺ and amino acids.⁸

Impact on wine aroma

Low production of acetate esters has been attributed to low enzymatic activity of esterases and a lack of ATF1-2 genes responsible for the alcohol acetyltransferases required for the production of volatile aroma-active esters.^9,10 Desirable oenological properties include low production of acetic acid, ethyl acetate, acetaldehyde and acetoin, medium production of H₂S, and medium to high resistance to SO₂.^2,3,5,6 Furthermore, some strains of T. delbrueckii have been shown to enhance volatile thiols in Sauvignon blanc.^5,11

Effect on malolactic fermentation

Most T. delbrueckii strains consume malic acid. The consumption level is strain dependent and vary from 10 – 30% of malic acid consumption.^9,12 Supplementation with complex nutrients, such as Fermaid^® E-blanc and OptiMUM White™ (both from Lallemand), was shown to stimulate malic acid consumption.⁹

Commercial products

Several commercial starter cultures of T. delbrueckii are available as active dry yeast in monoculture (Table 1). Mixed cultures with S. cerevisiae (Oenoferm^® Wild & Pure) and with S. cerevisiae and Lachancea thermotolerans (Viniflora^® Melody™) are also available.

Torulaspora delbrueckii is also available in Zymaflore^® ÉgideTDMP, which is used as a bioprotectant on grapes or in must to reduce the need for SO₂.

References

1. Albertin, W., Chasseriaud, L., Comte, G., Panfili, A., Delcamp, A., Salin, F., Marullo, P. & Bely, M., 2014. Winemaking and bioprocesses strongly shaped the genetic diversity of the ubiquitous yeast Torulaspora delbrueckii. PLOS One 9(4), e94246.
2. Azzolini, M., Tosi, E., Lorenzini, M., Finato, F. & Zapparoli, G., 2015. Contribution to the aroma of white wines by controlled Torulaspora delbrueckii cultures in association with Saccharomyces cerevisiae. World Journal of Microbiology and Biotechnology 31, 277 – 293.
3. Benito, S., 2018. The impact of Torulaspora delbrueckii yeast in winemaking. Applied Microbiology and Biotechnology 102, 3081 – 3094.
4. Morata, A., Escott, C., Bañuelos, M.A., Loira, I., Manuel del Fresno, J., González, C. & Suárez-Lepe, J.A., 2020. Contribution of non-Saccharomyces yeasts to wine freshness. Biomolecules 10, 34.
5. Ramírez, M. & Velázquez, R., 2018. The yeast Torulaspora delbrueckii: An interesting but difficult-to-use tool for winemaking. Fermentation 4, 94.
6. Zhang, B-Q., Luan, Y., Duan, C-Q. & Yan, G-L., 2018. Use of Torulaspora delbrueckii co-fermentation with two Saccharomyces cerevisiae strains with different aromatic characteristic to improve the diversity of red wine aroma profile. Frontiers in Microbiology 9, 606.
7. Kemsawasd, V., Viana, T., Ardö, Y. & Arneborg, N., 2015. Influence of nitrogen sources on growth and fermentation performance of different wine yeast-species during alcoholic fermentation. Applied Microbiology and Biotechnology 99, 10191 – 10207.
8. Roca-Mesa, H., Sendra, S., Mas, A., Beltran, G. & Torija, M-J., 2020. Nitrogen preferences during alcoholic fermentation of different non-Saccharomyces yeasts of oenological interest. Microorganisms 8, 157.
9. Mecca, D., Benito, S., Beisert, B., Brezina, S., Fritsch, S., Semmler, H. & Rauhut, D., 2020. Influence of nutrient supplementation on Torulaspora delbrueckii wine fermentation aroma. Fermentation 6, 35.
10. Tondini, F., Lang, T., Chen, L., Herderich, M. & Jiranek, V., 2019. Linking gene expression and oenological traits: Comparison between Torulaspora delbrueckii and Saccharomyces cerevisiae strains. International Journal of Food Microbiology 294, 42 – 49.
11. Renault, P., Coulon, J., Moine, V., Thibon, C. & Bely, M., 2016. Enhanced 3-sulfanylhexan-1-ol production in sequential mixed fermentation with Torulaspora delbrueckii/Saccharomyces cerevisiae reveals a situation of synergistic interaction between two industrial strains. Frontiers in Microbiology 7, 293.
12. Du Plessis, H., Du Toit, M., Hoff, J.W., Hart, R.S., Ndimba, B.K. & Jolly, N.P., 2017. Characterisation of non-Saccharomyces yeasts using different methodologies and evaluation of their compatibility with malolactic fermentation. South African Journal of Enology and Viticulture 38, 46 – 63.

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