Penicillin G acylase (PGA) is a commercially important enzyme that cleaves penicillin G to 6-amino penicillanic acid (6-APA) and phenyl acetic acid (PAA). The strain Bacillus badius has been identified as potential producer of PGA. A detailed calorimetric investigation on PGA production was carried out to enable generation of thermokinetic data possible for commercial application. Reaction calorimetric studies coupled with respirometric studies suggested that enzyme activity of the species B. badius was calorimetrically traceable. Three phases of growth were distinctly noticeable in the metabolic heat-time curve. Increase in enzymatic activity with restricted growth confirmed intracellular nature of the production process. The estimated heat yields due to biomass growth, 10.026 kJ/g, substrate consumption 22.761 kJ/g, and oxygen uptake 383 +/- 10 kJ/mol helped to understand the energetic of the organism under study. Low oxycalorific coefficient confirmed the existence of fermentation-coupled metabolism of B. badius.