J. Inst. Brew. vol.112:2 (2006) Altered Patterns of Maltose and Glucose Fermentation by Brewing and Wine Yeasts Influenced by the Complexity of Nitrogen Source

Altered Patterns of Maltose and Glucose Fermentation by Brewing and Wine Yeasts Influenced by the Complexity of Nitrogen Source

Margareth Batistote¹, Sandra Helena da Cruz² and José Roberto Ernandes^1,3
¹ Departamento de Bioquímica e Tecnologia Química, Instituto deQuímica, UNESP – São Paulo State University, PO Box 335,14801-970 – Araraquara, SP, Brazil.
² Departamento de Agroindústria, Alimentos e Nutrição, EscolaSuperior de Agricultura “Luiz de Queiroz”, USP –University of São Paulo, PO Box 09, 13418-900, Piracicaba, SP, Brazil.
³ Corresponding author. E-mail: ernandes@iq.unesp.br

J. Inst. Brew. 112(2), 84–91, 2006 | VIEW ARTICLE

ABSTRACT
Maltose and glucose fermentations by industrial brewing and wine yeasts strains were strongly affected by the structural complexity of the nitrogen source. In this study, four Saccharomyces cerevisiae strains, two brewing and two wine yeasts, were grown in a medium containing maltose or glucose supplemented with a nitrogen source varying from a single ammonium salt (ammo-nium sulfate) to free amino acids (casamino acids) and peptides (peptone). Diauxie was observed at low sugar concentration for brewing and wine strains, independent of nitrogen supplementation, and the type of sugar. At high sugar concentrations altered patterns of sugar fermentation were observed, and biomass accumulation and ethanol production depended on the nature of the nitrogen source and were different for brewing and wine strains. In maltose, high biomass production was observed under pep-tone and casamino acids for the brewing and wine strains, how-ever efficient maltose utilization and high ethanol production was only observed in the presence of casamino acids for one brewing and one wine strain studied. Conversely, peptone and casamino acids induced higher biomass and ethanol production for the two other brewing and wine strains studied. With glucose, in general, peptone induced higher fermentation performance for all strains, and one brewing and wine strain produced the same amount of ethanol with peptone and casamino acids supplementation. Ammonium salts always induced poor yeast performance. The results described in this paper suggest that the complex nitrogen composition of the cultivation medium may create conditions resembling those responsible for inducing sluggish/stuck fermentation, and indicate that the kind and concentration of sugar, the complexity of nitrogen source and the yeast genetic background influence optimal industrial yeast fermentation performance.

Key words:
Amino acids, fermentation, glucose utilization, in-complete fermentation, maltose utilization, nitrogen metabolism, peptides, Saccharomyces, yeast.