RESUMO
It was shown that eight stages of transition are observed in the heating process of Spirulina platensis cells in temperature range 5-140 degrees C. The first stage covers the temperature range 5-53 degrees C with maximum approximately 45 degrees C. The heat evolved in this temperature range is equal to 380 +/- 20 J/g of dry biomass, it does not change at scanning rate lower than 0.083 degrees C/min and belongs, mainly, to cell respiration in a stationary regime, in the dark. It was shown that endotherm approximately 66 degrees C belongs to denaturation of C-phycocyanin which denaturates in solutions with Td = 64.2 degrees C, deltaHd = 34.7 +/- 2.1 J/g and for it deltaHd(cal)/deltaH(V.H) is equal to 10.8 +/- 1.2. The endotherms with Td equal to 58 and 88 degrees C are connected with denaturation of phycobilisome proteins and endotherm with Td = 48 degrees C and deltaHd = 4.2J/g of dry biomass-with denaturation of protein which, apparently, is connected with cell respiration.
