Selection and subsequent physiological characterisation of industrial Saccharomyces cerevisiae strains during continuous growth at sub- and- supra optimal temperatures
A phenotypic screening of 12 industrial yeast strains and the well-studied laboratory strain CEN.PK113-7D at cultivation temperatures between 12 {degrees}C and 40 {degrees}C revealed significant differences in maximum growth rates and temperature tolerance. Two Saccharomyces cerevisiae strains, one performing best at sub-, and the other at supra-optimal temperatures, plus the laboratory strain, were selected for further physiological characterization in well-controlled bioreactors. The strains were grown in anaerobic chemostats, at a fixed specific growth rate of 0.03 h-1 and sequential batch cultures at 12, 30, and 39 {degrees}C. We observed significant differences in biomass and ethanol yields on glucose, biomass protein and storage carbohydrate contents, and biomass yields on ATP between strains and cultivation temperatures. Increased temperature tolerance coincided with higher energetic efficiency of cell growth, indicating that temperature intolerance is a result of energy wasting processes, such as increased turnover of cellular components (e.g. proteins) due to temperature induced damage.