Optimisation of a Fully Defined Medium for Yeast Fermentation Studies

A. I. Kennedy, B. Taidi*, J. L. Dolan, J. A. Hodgson

Scottish Courage Brewing Ltd., Technical Centre, 160 Canongate, Edinburgh, EH8 SOD, Scotland, UK

Article history:
Received September 10, 1997
Accepted November 14, 1997

Key words:
defined medium, wort fermentation, yeast, esters, carbohydrates

Summary:
It is known that there can be significant batch to batch variation in the cltemical composition of brewery worts. Thus, wort does not provide a reproducible substrate for laboratory experiments when investigating yeast behaviour such as fermentation profile, uptake of nutrients and the formation of by-products. Experiments were devised to optimise a fully defined medium which reflected the composition of industrially produced wort. The aim was to provide a reproducible medium for laboratory studies which was also comparable to production zvort in supporting yeast growth and fermentation. A mixture of amino acids, carbohydrates, vitamins and trace elements was developed based on analyses of brewery worts. This medium proved to be an excellent fermentation substrate for lager yeast giving results similar to those obtained with wort. Ale yeast could not fully attenuate the defined medium but othenvise produced results typical of wort fermentation.

*Corresponding author:           behnam.taidi@scbrew.co.uk
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