Use of a modified alcohol dehydrogenase, ADH1, promoter in construction of diacetyl non-producing brewer's yeast.

The bacterial gene, encoding alpha-acetolactate decarboxylase (alpha-ALDC), was expressed in a bottom-fermenting brewer's yeast under the control of a modified Saccharomyces cerevisiae alcohol dehydrogenase (ADH1) promoter which lacks the upstream regions from -800 bp to -1500 bp. In pilot scale brewing conditions, the level of alpha-ALDC produced was high enough to reduce the concentration of diacetyl so that lagering was not required. alpha-ALDC active brewer's yeast strains were also shown to be suitable for high gravity brewing.