Open AccessAdaptive evolution of the lager brewing yeast S accharomyces pastorianus for improved growth under hyperosmotic conditions and its influence on fermentation performance
Author(s) -
Ekberg Jukka,
Rautio Jari,
Mattinen Laura,
Vidgren Virve,
Londesborough John,
Gibson Brian R.
Publication year - 2013
Publication title -
fems yeast research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.991
H-Index - 92
eISSN - 1567-1364
pISSN - 1567-1356
DOI - 10.1111/1567-1364.12038
Subject(s) - fermentation , biology , yeast , trehalose , food science , brewing , saccharomyces cerevisiae , osmotic shock , strain (injury) , biochemistry , ethanol , diacetyl , ethanol fermentation , gene , anatomy
Abstract An adaptive evolution method to obtain stable S accharomyces pastorianus brewing yeast variants with improved fermentation capacity is described. The procedure involved selection for rapid growth resumption at high osmotic strength. It was applied to a lager strain and to a previously isolated ethanol‐tolerant strain. Fermentation performance of strains was compared at 15 ° P wort strength. A selected osmotolerant variant of the ethanol‐tolerant strain showed significantly shorter fermentation time than the parent strain, producing 6.45% alcohol by volume beer in 4–5 days with mostly similar organoleptic properties to the original strain. Diacetyl and pentanedione contents were 50–75% and 3‐methylbutyl acetate and 2‐phenylethyl acetate 50% higher than with the original strain, leading to a small flavour change. The variant contained significantly less intracellular trehalose and glycogen than the parent. Transcriptional analysis of selected genes at 24 h revealed reduced transcription of hexose transport genes and increased transcription of the MAL x1 and MAL x2 genes, responsible for α‐glucoside uptake and metabolism. It is suggested that an attenuated stress response contributes to the improved fermentation performance. Results show that sequential selection for both ethanol tolerance and rapid growth at high osmotic strength can provide strains with enhanced fermentation speed with acceptable product quality.