Effect of Sugar Catabolite Repression in Correlation with the Structural Complexity of the Nitrogen Source on Yeast Growth and Fermentation
Sandra Helena da Cruz 1, Margareth Batistote 1 and José Roberto Ernandes 1, 2
1 Departamento de Bioquímica e Tecnologia Química, Instituto de Química, Universidade Estadual Paulista (UNESP), PO Box 335, 14801-970 - Araraquara, SP, Brazil. Phone: 55-16-2016674. Fax: 55-16-2227932.
2 Corresponding author. E-mail: ernandes@iq.unesp.br
J. Inst. Brew. 109(4), 349-355, 2003 | VIEW ARTICLE
ABSTRACT
Biomass and ethanol production by industrial Saccharomyces
cerevisiae strains were strongly affected by the structural
complexity of the nitrogen source during fermentation in media
containing galactose, and supplemented with a nitrogen source
varying from a single ammonium salt (ammonium sulfate) to
free amino acids (casamino acids) and peptides (peptone).
Diauxie was observed at low galactose concentrations independent
of nitrogen supplementation. At high sugar concentrations
altered patterns of galactose utilisation were observed. Biomass
accumulation and ethanol production depended on the nature
of the nitrogen source and were different for baking and brewing
ale and lager strains. Baking yeast showed improved galactose
fermentation performance in the medium supplemented with casamino
acids. High biomass production was observed with peptone and
casamino acids for the ale brewing strain, however high ethanol
production was observed only in the presence of casamino acids.
Conversely, peptone was the nitrogen supplement that induced
higher biomass and ethanol production for the lager brewing
strain. Ammonium salts always induced poor yeast performance.
The results with galactose differed from those obtained with
glucose and maltose which indicated that supplementation with
a nitrogen source in the peptide form (peptone) was more positive
for yeast metabolism, suggesting that sugar catabolite repression
has a central role in yeast performance in a medium containing
nitrogen sources with differing levels of structural complexity.
Key words:
Amino acids, fermentation, nitrogen metabolism, peptides,
Saccharomyces, sugar catabolite repression, yeast.
Publication no. G-2003-1309-218 ©2003 The Institute & Guild of Brewing