Relationship between thermal behaviour, fermentation performance and fatty acid composition in two strains of Saccharomyces cerevisiae.

Two Saccharomyces cerevisiae strains, one specifically of S. cerevisiae and another belonging to the physiological race S. uvarum, exhibited associative and dissociate thermal profiles, respectively. The S. cerevisiae subsp. uvarum strain, which displayed the dissociative profile, was characterized by a higher aptitude for fermenting glucose in a superoptimal temperature range as well as by a lower fatty acid unsaturation degree. On the other hand, both strains exhibited a similar fatty acid composition modulation pattern with regard to temperature: the unsaturation level presented two relative maxima at 15 and 40 degrees C. However, on the basis of Central Composite Design results, supplementation with an oleic acid source under semi-anaerobic conditions did not improve the fermentative performances in either strain. The modelling of fermentation rate in relation to certain variables indicated that the fermentative performance at superoptimal temperatures, and particularly the optimal temperature (Topt) and maximal temperature (Tmax) of the strain displaying a dissociative profile, could be increased by acting on medium composition.