Growth of Saccharomyces Cerevisiae and Saccharomyces Uvarum in a Temperature Gradient Incubator

A temperature gradient incubator has been used to determine the effect of temperature on the growth of strains of Saccharomyces cerevisiae and Saccharomyces uvarum (including lager brewing yeasts formerly classified as Saccharomyces carlsbergensis). The maximum temperatures for growth (Tmax) for all strains of S. cerevisiae examined were in the range 37.5°C-39.8°C and the optimum temperatures for the most rapid initial growth (Topt) were in the range 30.0°C-35.0°C. Strains of S. uvarum, however, formed two distinct groups: Group A (including all brewing strains of S. uvarum tested) had Tmax values 31.6°C-34.0°C and Topt values 26.8°C-30.4°C; Group B had Tmax values 38.2°C-40.0°C and Topt values 30.0°C-34.6°C. It is proposed, therefore, that the species name S. carlsbergensis should be re-introduced and applied to those strains of S. uvarum (Group A) which have the lower Tmax values. Minimum temperatures for growth (Tmin) of the yeasts were not investigated as initial studies had shown that they could not be measured satisfactorily. Measurements of the generation times for one brewing strain of S. cerevisiae and one brewing strain of S. uvarum (Group A) over the temperature range 6.0°C-22.0°C have shown that there are significant differences between the yeasts at the lower end of the temperature range and that the relationship between generation time (GT) and temperature (T) for both yeasts closely follows the mathematical expression: