The use of the heat-flux calorimeter BSC-81 as a chemostat is described. The technique was applied to study the heat generation rate by continuous cultures of the yeast Kluyveromyces fragilis NRRL 1109 as a function of specific growth rate. The maintenance energy dissipation was detd. as 0.025 W/g dry wt. The proportionality coeff. between heat dissipation and O2 consumption was const. at 441 kJ/mol. [on SciFinder (R)]