Exploring Differential Scanning Calorimetry as a tool for evaluating freezing and thawing sensitivity in Saccharomyces cerevisiae

WU, ANGEL; SANTAGAPITA, PATRICIO R.; BUERA, M. PILAR; CERRUTTI, PATRICIA; GALVAGNO, MIGUEL A.

Pinamar, Argentina

Congreso; XLI Annual Meeting of the Argentine Society of Biochemistry and Molecular Biology; 2005

Sociedad Argentina en Investigaciones en Bioquímica y Biología Molecular (SAIB)

Differential Scanning Calorimetry (DSC) was used to evaluate the freezing and thawing (F/T) resistance of two commercial S. cerevisiae strains having high (O) and low (NO) tolerance to osmotic stress. Cells in stationary phase of growth were exposed to two cycles of freezing at -20ºC for 20 and 4 h, respectively, and thawing at 25ºC, after being exposed to various physical and chemical mild stresses. Cells were used for DSC runs performed at 10°C/min from -100 to110°C. The most adequate transitions to analyze in relation to cell viability after F/T treatments were those attributed to protein denaturation. Thermograms showed two protein populationscorresponding to low and high denaturation temperatures: 43-55ºC (P1) and 65-80ºC (P2) respectively. Apparent enthalpy (J/g protein) change showed that strain O had a relatively higher resistance to F/T treatment than strain NO (ΔH = 30 J/g protein). On the other hand some pre-treatments (v.g., temperature, ethanol and H2O2) increased both protein denaturation temperature and thermal resistance after F/T. The analysis of data clearly showed that theDSC can be a very useful tool to analyze the impact of different stress factors on F/T tolerance.