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Brewers Yeast Modification: Effects Both on Diacetyl Production and Alcohol Formation*
L. Strack and U. Stahl

New industrial brewing yeasts*1 have been generated by introduction of two genes involved in valine biosynthetic pathway in order to clarify their roles for the reduction of diacetyl content in beer. The Saccharomyces cerevisiae genes as well as lager*2 genes both BAT1 (encoding branched-chain amino acid aminotransferase) and BAT2 (encoding branched-chain amino acid aminotransaminase) have been transferred into brewer?s yeast. Within this approach it was possible to decrease diacetyl levels at the end of main fermentation without affecting the by-product profile of the beer negatively. Furthermore, our results pointed to the regulation of these genes concerning diacetyl formation.

Descriptors: brewers yeast, metabolic engineering, diacetyl, maturation

BrewingScience Monatsschrift fr Brauwissenschaft, 63 (January/February 2010), pp. 6-13