WINETECH Technical Yearbook 2020

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 (Porter et al ., 2019; Kemsawasd et al ., 2015; Roca-Mesa et al ., 2020). • 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 (Roca-Mesa et al ., 2020). This regulatory system is referred to as nitrogen catabolite repression. • While many nitrogen sources can sus- tain high maximum specific growth rates, phenylalanine, serine and tyro-

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 (Lachance & Kurtzman, 2011). 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 Lachancea thermotolerans reproduces sexually through the formation of spherical ascospores and asexually through multi­ lateral budding (Morata et al ., 2018). 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). yeast (Porter et al ., 2019). WHAT IT LOOKS LIKE

Lachancea thermotolerans yeast and its role in winemaking

AUGUST 2020

EVODIA SETATI: Department of Viticulture and Oenology, Stellenbosch University, Stellenbosch KEYWORDS: Non- Saccharomyces yeasts, lactic acid, β -lyase, β -glucosidase

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