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A ‘fine’ way to use Botrytis

13 Oct 2017
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Little more than a year ago Rachel Self’s wine knowledge didn’t extend much beyond knowing what styles she liked to drink. Now she’s well on track to potentially changing one of the key steps in the winemaking process.

Supported by scholarships from Wine Australia and Macquarie University, Rachel’s PhD project is developing a biological approach to wine fining, using Botrytis cinerea, that could eliminate the traditional use of bentonite.

Rachel Self in laboratory
Rachel Self

That would save significant amounts of time and money (previous research has suggested that up to 5 per cent of total wine volume can be lost by being sequestered in bentonite lees) as well as removing the risk of bentonite affecting the character of the wine by absorbing aroma and flavour molecules.

There would also be important environmental benefits in not having to use large amounts of bentonite – a mined and imported resource – then dispose of the lees as waste.

The project came about in a rather roundabout way. Rachel completed undergraduate studies at the Queensland University of Technology (QUT) in microbiology and biotechnology and initially was looking to do a PhD in fermentation or some other area of food science.

When plans kept falling through she considered ‘just going and getting a job’, but then a chance meeting with an academic led to an offer to enter the world of wine research. 

Her PhD is being taken through Macquarie University in Sydney, but thanks to cooperation between the two institutions she does her work in the labs at QUT – and has supervisors at both universities. ‘I wasn’t in a position to move to do the PhD so they brought the PhD to me’, she said. ‘I really appreciate the support.’ 

The twist is that Rachel is originally from Sydney. And she used to be a teacher – returning to university as a mature age student a few years ago.

Her project builds on research carried out by one of her Macquarie-based supervisors, Dr Steve Van Sluyter. He published a paper in 2013 showing the potential for Botrytis cinerea protease to remove the grape proteins that create haze in white wines, and to do it under normal winemaking conditions.

However, that project involved some degree of genetic modification that is not permissible in the Australian wine sector. Rachel is working on an approach that is GM-free.

The basic science seems relatively straight forward. During infection, Botrytis releases several proteases (enzymes), some of which appear to remove the unwanted proteins. There are complications, however. Botrytis grown in liquid culture for enzyme production also produces laccases (enzymes that can degrade wine quality) and glycans (carbohydrates that could clog filters during winemaking).

‘There have been lots of surprises along the way’, Rachel said. ‘Botrytis is a very well researched area and for the most part that is great. Some of my friends who have very novel projects tell me how easy it must be doing a subject with so much research. But it means you have to know all that research – and not all of it always applies.

‘Overall, there have been some steep learning curves on this journey, but I am enjoying every part of it.’

- Rachel Self, PhD student, Macquarie University

Most importantly, progress to date has been encouraging. Rachel has seen promising results in lab trials and is in the process of scaling up protease production to 10 litre fermentation vessels.

The project is being assisted by Treasury Wine Estates. Rachel’s other supervisors are Associate Professor Junior Te'o (QUT) and Professor Michael Gillings (Macquarie University).

Applications for Wine Australia’s PhD and Masters by Research scholarships close 3 November 2017, more information is available here.

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This content is restricted to wine exporters and levy-payers. Some reports are available for purchase to non-levy payers/exporters.