Yeast ADHI disruption: A way to promote carbonyl compounds reduction in alcohol-free beer production

Alcohol-free beers are usually characterized by worty off-flavors and the lack of the pleasant fruity or ester aroma found in regular beers. Enhancing yeast reduction of 3-methylthiopropionaldehyde, 3-methylbutanal, and 2-methylbutanal appears to be a good means of improving the organoleptic quality of alcohol-free beers. Upon screening of various Saccharomyces cerevisiae yeasts for in vitro reductase activity, a haploid adh0 strain emerged as the most efficient yeast for nicotinamide adenine dinucleotide phosphate (reduced form) (NADPH)-dependent Strecker aldehyde reduction. Tetrad analysis of diploids (adh0 x 15D wild-type) demonstrated the predominant role of adh1 mutation to enhance aldehyde reductase. Consequent to such alcohol dehydrogenase gene disruption, acetaldehyde accumulates, although partly oxidized into acetic acid by the NADP cofactor. We propose that regeneration of this cofactor in adh1 strains can be improved by promoting NADPH-dependent aldehyde reductase activity.