Alternate method of calculating the free-energy change accompanying the growth of saccharomyces cerevisiae (Hansen) on three substrates.

A method is described for determining the free energy of formation of the cells of Saccharomyces cerevisiae (Hansen) that are formed as the result of anaerobic growth on glucose, and aerobic growth on glucose and ethanol. The method is based on the direct relationship that exists between the enthalpy changes and the free-energy changes that accompany the oxidation of 1 g cellular material formed during these growth reactions and the degree of reduction of the same material. When the results of these calculations are used together with the free energies of formation of the reactants and of other products of a given growth reaction, it becomes possible to calculate the free-energy change accompanying this reaction. These free-energy changes are in excellent agreement with those calculated by another method based on the hypothesis that the free-energy change accompanying the conversion of the substrate plus other reactants into cellular material plus other products is equal to zero.