Thiaisoleucine resistant mutants in Saccharomyces carlsbergensis increase the content of d-amyl alcohol in beer

Abstract

Four presumably dominant thiaisoleucine resistant mutants of a brewing strain of Saccharomyces carlsbergensis were previously shown to produce more d-amyl alcohol than the parent strain when grown in synthetic minimal medium with aeration. In the present work an increased production of d-amyl alcohol was also found in fermenting wort under brewing conditions resulting in a beer with an altered ratio between d-amyl alcohol and isoamyl alcohol. The synthesis of 2,3-pentanedione plus its precursor, α-aceto-α-hydroxybutyrate, was generally higher in the mutants. The mutants showed a somewhat lower rate of increase in cell concentration during fermentation than the parent strain. With respect to other analytical data and taste, the three mutants isolated after moderate mutagenesis did not show deviations outside the range of the parent. One mutant obtained from a more heavity mutagenized culture deviated in several respects. © 1979 Carlsberg Laboratory.