Fit-for-Purpose Yeast and Bacteria via Directed Evolution

Summary

Objectives

Develop non-GM yeast and bacterial strains for commercial release with better stress tolerance and performance, including one or more of the following properties

  • greater tolerance of low nutrient availability, cold or inhibitory compounds
  • enhanced flocculation and metabolism of malic acid, and reduced H2S and SO2 formation
  • tailored performance in ‘extreme’ juices e.g. from overripe or Botrytis affected grapes

Background

A most fundamental requirement of winemaking is reliable and predictable fermentations: reliable in terms of trouble-free completion and predictable in terms of fermentation duration, yeast/bacterial supplement needs and appropriate production of desirable and undesirable metabolites.

While more than 200 commercial yeast strains are available, strains able to de-acidify (metabolise malic acid) or more efficiently ferment must from Botrytis affected fruit are not.  Strains with flocculation or suspension behaviour are also not readily available, and these properties would make strains more suitable for different applications (e.g. tank vs. barrel fermentation) and improve production efficiency. Malolactic fermentation remains unreliable despite advances and availability of more robust strains.

Research approach

The approach used in this project to generate the new strains is directed evolution guided by an understanding of the genes and physiochemical stresses involved. The utility of the new strains will be evaluated through laboratory and pilot scale fermentations and industry trials together with evaluation of experimental wines.

Industry benefit

The knowledge and the new strains generated by this project will give winemakers increased ability to manage fermentation efficiency and wine composition.