Heat generation is a very conspicuous phenomenon in large scale bioreactors and could in principle quite easily be measured by the temp. increase of the cooling water. Taking yeast cultures growing on a mixed oxido-reductive metab. for various reasons as an example, this paper demonstrates how heat dissipation measurements may be used in combination with other convenient online measurements order to obtain a quant. estn. of the nature of the on-going metab. and of the current overall stoichiometry. The application of such measurements to controlling fed-batch cultures is also discussed. [on SciFinder (R)]