Maltose and glucose fermentation by industrial brewing and wine yeasts strains was 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  media containing maltose or glucose 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 sugar concentration for brewing and wine strains independent of nitrogen supplementation and the kind of sugar. At high sugar concentrations altered patterns of sugars 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 peptone and casamino acids for the brewing and wine strains, however efficient maltose utilization and high ethanol production was observed only in the presence of casamino acids for one brewing and one wine strain. Conversely, peptone and casamino acids induced higher biomass and ethanol production for the two other brewing and wine strains. In glucose, in general, peptone induced higher fermentation performance for all strains. Ammonium salts always induced poor yeast performance. Altered fermentative behavior among industrial yeasts induced by the complexity of nitrogen source appears to be correlated to the differing ability of peptides utilization by the brewing and wine strains of Saccharomyces cerevisiae. The results described in this work 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 interfere with the industrial yeast fermentation performance.