Effects of temperature, pH and sugar concentration on the growth parameters of Saccharomyces cerevisiae, S. kudriavzevii and their interspecific hybrid.

The effects of temperature, pH and sugar concentration (50% glucose+50% fructose) on the growth parameters of Saccharomyces cerevisiae T73, S. kudriavzevii IFO 1802(T) and the hybrid strain S. cerevisiae x S. kudriavzevii W27 were studied by means of response surface methodology based in a central composite circumscribed design. Lag phase could not be properly modelled in the wine model system, where yeasts started the fermentation in few hours after inoculation. In the case of the maximum specific growth rate (micro(max)), the temperature was the most important variable for three yeasts, although the effects of sugar concentration (in T73 and W27) and pH (W27 and 1802) were also significant (p<0.05). The only retained interaction was between the variables temperature and pH for yeast 1802. The polynomial equations built for micro(max) were used both to assess the behaviour of yeasts as a function of the factors and to predict their growth. In the case of temperature, the profiles obtained by the equations showed that response of the hybrid W27 was similar to T73 and different to 1802. When pH was the factor under study, the response of the hybrid W27 was closer to 1802 than yeast T73. For sugar concentration, the response of the hybrid W27 was similar to T73 but different to 1802. To the best of our knowledge, this is the first time that predictive models are used to assess and compare the response of a hybrid strain with respect to its parental species. The information obtained could also be useful to estimate the possible effect of climatic change on yeast growth.