Results from the investigation of the cultivation of Bacillus thuringiensis var galleriae in a bench-scale calorimeter (Bio-RCl) are presented in this work. On-line torque measurements were used to correct the baseline shift resulting from the variation of rheological properties of the medium. Heat measurements, combining with the balances of mass, degree of reduction and energy, are used to estimate the consumption of yeast extract, thus more accurate stoichiometry of the growth reaction in semi-defined medium was determined. The correlations between the rate of heat production and other relevant process variables, during the growth of Bg., were explored, and such correlations and stoichiometry of growth form the basis for using on-line data of heat production, together with other continuously measured information, for the optimization of media and the monitoring and control of the growth and sporulation processes of Bg., particularly in fed-batch and continuous cultures.