Poster Presentation Australian Society for Microbiology Annual Scientific Meeting 2023

Exploring the Terroir: Bioprospecting Indigenous Vineyard Yeast for Sustainable Winemaking (#118)

Natalia Caliani 1 2 , Cassandra Collins 1 2 , Kelsey Laverne 1 3 , Joanna Sundstrom 1 2 , Eveline Bartowsky 1 4 , Anthony Borneman 1 5 , Kim Chalmers 1 6 , Paul Boss 1 7 , Vladimir Jiranek 1 2 , Krista Sumby 1 2
  1. University of Adelaide - ARC Training Centre for Innovative Wine Production, Urrbrae, SA, Australia
  2. Wine Science Discipline, School of Agriculture Food & Wine - Waite Research Institute, University of Adelaide, Urrbrae, SA, Australia
  3. Ecole Nationale Supérieure des Sciences Agronomiques de Bordeaux Aquitaine , Gradignan, Nouvelle-Aquitaine, France
  4. Lallemand Australia, Edwardstown, South Australia, Australia
  5. The Australian Wine Research Institute, Adelaide, South Australia, Australia
  6. Chalmers Wines Australia Pty Ltd, Merbein, Victoria, Australia
  7. CSIRO Agriculture and Food, Glen Osmond, South Australia, Australia

Vineyards are an essential part of the ‘terroir’, which encompasses the soil, climate, and viticultural practices, which are intimately linked to the regional typicity of wine. The ‘terroir’ also includes the unique microbiological makeup which defines distinctive wine attributes. Within this microbial terroir, we find non-Saccharomyces yeasts, which have gained the interest of winemakers worldwide, as they could be used as a microbiological tool to enhance wine quality (aroma, texture, and length).  However, winemakers currently only have access to a handful of non-Saccharomyces strains, and this project aims to diversify their choices.

Some of the main characteristics of a new yeast candidate are linked to stress tolerance (ethanol, sulfur dioxide, pH, and deficient nitrogen availability), fermentation performance, desirable secondary metabolite production, and the ability to survive freeze-drying.

In this study, we created an indigenous yeast library containing 600+ single colonies isolated from the Chalmers Merbein vineyard (Victoria, Australia) and Yalumba Pewsey Vale vineyard (SA, Australia). They were identified using internal transcribed spacer (ITS) sequencing.  Nineteen of the Chalmers isolates were pre-screened to assess their ethanol and SO2 tolerance, using YPD agar spiked with increasing concentrations of both stressors, based on species identification. Of these, only thirteen isolates showed some degree of tolerance. Their sugar consumption was evaluated in a chemically defined grape juice medium (CDGJM), adding twelve Pewsey Vale isolates to the screening. Lastly, SO2 tolerance was evaluated using CDGJM spiked with 20, 35, 50, and 65 ppm using an automated fermentation platform.

The most promising candidates (Hanseniaspora, Kazachstania, Metschnikowia, Saccharomyces, and Torulaspora) withstood 65 ppm SO2, similar to the Saccharomyces cerevisiae control. They will be tested further for their volatile production in white and red grape juice, with a view towards broadening the portfolio of winemaking starter cultures.