A novel heat-flux calorimeter was used to study the growth of Kluyveromyces fragilis on a variety of C substrates. Heat liberated was directly related to biomass formed and also to O2 consumed. Heat yield coeffs. derived from these relationships allowed the development of stoichiometries describing yeast growth. Since the sensitivity and speed of response of the calorimeter are higher than those of many other monitoring systems, such a system could be advantageously used to control fermns. [on SciFinder (R)]