Lachancea thermotolerans yeast and its role in winemaking

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

PHOTO: Shutterstock.

L. thermotolerans contributes to the production of wines with enhanced mouthfeel, floral notes, fruitiness and freshness.

Current and previous names

Lachancea thermotolerans is the type species of the genus Lachancea, which was proposed and validated in 2003 following a re-evaluation of species relatedness using a combination of ribosomal RNA genes. Prior to that, this species had carried various designations including Zygosaccharomyces thermotolerans, Saccharomyces thermotolerans and Kluyveromyces thermotolerans.1

Where it is found

Lanchancea thermotolerans has been isolated from soil, insects, plants and fruit, in particular grapes. Indeed, grape must was highlighted as a major source of this yeast.2

What it looks like

Lachancea thermotolerans reproduces sexually through the formation of spherical ascospores and asexually through multilateral budding.3 It forms spherical to ellipsoidal cells that are not easily distinguishable from Saccharomyces cerevisiae, although the cells are slightly smaller (3 – 6 x 6 – 8 µm).

The cells form creamy colonies with butyrous texture when growing on yeast-peptone-dextrose agar and malt extract agar, while on Wallerstein nutrient agar the colonies are dark green, rough and raised with a white margin.

Nitrogen metabolism

  • L. thermotolerans grows well in complex media containing organic and inorganic nitrogen sources. However, strains might vary in terms of growth, yeast assimilable nitrogen (YAN) consumption and fermentation rates in such matrices, compared to media with ammonia only or amino acids only.2,4,5
  • In complex matrices, such as grape must, L. thermotolerans displays nitrogen assimilation patterns similar to those of S. cerevisiae, which could result in nutrient competition between the two species.
  • In general, ammonia, as well as the amino acids tyrosine, methionine, cysteine and isoleucine, are assimilated earlier, while aspartic acid, histidine, glycine and alanine are consumed after ammonia is exhausted.5 This regulatory system is referred to as nitrogen catabolite repression.
  • While many nitrogen sources can sustain high maximum specific growth rates, phenylalanine, serine and tyrosine have been shown to also sustain viability at the beginning and late stages of the stationary phase.4

Alcohol and SO2 tolerance

  • Lanchancea thermotolerans is a Crabtree positive yeast (i.e. it displays a respiro-fermentative metabolism that allows it to ferment sugars even in the presence of excess oxygen).
  • Strains of L. thermotolerans have been widely described as moderate fermenters, able to produce 5 – 10% v/v ethanol, but unable to entirely ferment grape must.3,6,7
  • Consequently, co-inoculation with a stronger fermenter, such as Saccharomyces cerevisiae, is necessary in order to ferment grape must to dryness. However, in such mixed-culture fermentations L. thermotolerans strains only persist until the middle of fermentation.
  • Most strains can tolerate up to 7% v/v ethanol and standard SO2 levels (25 – 50 mg/L) typically used in winemaking, while a few show tolerance to higher levels of 8 – 10% v/v ethanol.2,8

The role of oxygen

The decline of L. thermotolerans during wine fermentation has been attributed to its sensitivity to low dissolved oxygen. Increased frequency of aeration interventions, such as punch downs, may enhance the persistence of L. thermotolerans strains.9,10,11

Sugar consumption and lactic acid production

  • Although L. thermotolerans can ferment both glucose and fructose, all strains display a glucophilic character and can produce anything between 0.3 and 16 g/L l-lactic acid, derived from pyruvate in the glycolytic pathway.6,7,8
  • The lactic acid is produced in the early stages of fermentation and can lead to reduction in pH by up to 0.5 units. The pH reduction improves wine colour intensity and stability by increasing the molecular SO2.8
  • Efficient lactic acid production is dependent on L. thermotolerans cell numbers, with a significant effect when the population is above 1 x 106 cfu/mL.8 Consequently, fermentation parameters, such as temperature and YAN levels that affect growth, also influence lactic acid production.8
  • The diversion of pyruvate to lactic acid can reduce the final ethanol levels in wine by 0.3 – 1% v/v. The best inoculation strategy to achieve efficient pH and ethanol reduction, is shown to be sequential inoculation of S. cerevisiae 48 hours after L. thermotolerans, with an inoculation ratio of 1 x 107 cfu/mL L. thermotolerans: 1 x 103 cfu/mL S. cerevisiae.3

Impact on wine aroma

Apart from the lactic acid production, L. thermotolerans contributes to wine aroma and flavour through fermentation derived metabolites, such as 2-phenylethanol, 2-phenylethyl acetate and ethyl lactate.3,8,12 Moreover, L. thermotolerans produces enzymes, such as β-glucosidases and β-lyases, that modulate the release of monoterpenes and thiols and therefore enhance the expression of varietal aromas.3 Overall, L. thermotolerans contributes to the production of wines with enhanced mouthfeel, floral notes, fruitiness and freshness.12

Commercially available products

Several L. thermotolerans active dry yeast (ADY) commercial preparations are now available. These include Viniflora® CONCERTO™ (CHr Hansen) and Level2 LAKTIA™ (Lallemand) as monocultures, as well as Viniflora® Melody™ (CHr Hansen) in mixed cultures with Torulaspora delbrueckii and S. cerevisiae, and Viniflora® Rhythm™ (CHr Hansen) in mixed culture with S. cerevisiae.

 

References

  1. Lachance, M.A. & Kurtzman, C.P., 2011. Lachancea Kurtzman (2003). In: Kurtzman, C., Fell J.W. & Boekhout, T. (eds). The yeasts: A taxonomic study, 5th edn. Elsevier, Amsterdam. pp 511 – 519.
  2. Porter, T.J., Divol, B. & Setati, M.E., 2019. Lachancea yeast species: Origin, biochemical characteristics and oenological significance. Food Research International 119, 378 – 389.
  3. Morata, A., Loira, I., Tesfaye, W., Bañuelos, M.A., González, C. & Suárez-Lepe, J.A., 2018. Lachancea thermotolerans applications in wine technology. Fermentation 4, 53.
  4. 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.
  5. 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.
  6. Benito, S., 2018. The impacts of Lachancea thermotolerans yeast strains on winemaking. Applied Microbiology and Biotechnology 102, 6775 – 6790.
  7. Hranilovic, A., Gambetta, J.M., Schmidtke, L., Boss, P.K., Grbin, P.R., Masneuf-Pomarede, I., Bely, M., Albertin, W. & Jiranek, V., 2018. Oenological traits of Lachancea thermotolerans show signs of domestication and allopatric differentiation. Scientific Reports 8, 14812.
  8. 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.
  9. Hansen, E.H., Nissen, P., Sommer, P., Nielsen, J.C. & Arneborg, N., 2001. The effect of oxygen on the survival of non-Saccharomyces yeasts during mixed culture fermentations of grape juice with Saccharomyces cerevisiae. Journal of Applied Microbiology 91, 541 – 547.
  10. Shekhawat, K., Bauer, F.F. & Setati, M.E., 2017. Impact of oxygenation on the performance of three non-Saccharomyces yeasts in co-fermentation with Saccharomyces cerevisiae. Applied Microbiology and Biotechnology 101, 2479 – 2491.
  11. Shekhawat, K., Porter, T.J., Bauer, F.F. & Setati, M.E., 2018. Employing oxygen pulses to modulate Lachancea thermotolerans – Saccharomyces cerevisiae Chardonnay fermentations. Annals of Microbiology 68, 93 – 102.
  12. Vilela, A., 2018. Lachancea thermotolerans, the non-Saccharomyces yeast that reduces the volatile acidity of wines. Fermentation 4, 56.

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

 

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