Beer with Reduced Ethanol Content Produced Using Saccharomyces cerevisiae Yeasts Deficient in Various Tricarboxylic Acid Cycle Enzymes

Radoslav Selecký^1,4 Daniela Šmogrovičová² and Pavol Sulo³
¹ Pivovary Topvar a.s., Krušovská 2092, 955 14 Topoľčany, Slovak Republic,
² Slovak University of Technology, Faculty of Chemical and Food Technology, Institute of Biotechnology and Food Science, Department of Biochemical Technology, Radlinského 9, 812 37 Bratislava, Slovak Republic
³ Comenius University, Faculty of Natural Sciences, Department of Biochemistry, Mlynská dolina, 842 15 Bratislava 4, Slovak Republic
⁴ Corresponding author. Email: Radoslav.selecky@topvar.sabmiller.com

J. Inst. Brew. 114(2), 97–101, 2008 | VIEW ARTICLE

ABSTRACT
A collection of Saccharomyces cerevisiae strains deficient in the tricarboxylic acid cycle enzymes activities has been examined for the production of beer with reduced ethanol content. Strains deficient in fumarase and α-ketoglutarate dehydrogenase encoded by the genes FUM1 (0.48%), KGD1 (0.42%) and KGD2 (0.48%) made non-alcoholic beers with an alcohol content lower than 0.5% (v/v). The rest of the yeast mutants also gave rise to low-alcoholic beers but with a slightly elevated ethanol concentration (mostly in the range of 0.57–0.84% and 1.64% for the lip5 mutant). Low ethanol content was compensated by the considerable increase of organic acids (citrate succinate, fumarate, and malate). In addition, some of the mutants released high levels of lactic acid (144 (fum1), 622 (kgd1) and 495 (kgd2) mg/L). Lactic acid protects beers against contamination and masks an unacceptable worty off-flavour.

Key words:
beer, Saccharomyces cerevisiae, tricarboxylic acid cycle.