The desorption rate of biogenic H2S during the batch growth of the sulfate-reducing bacterium Desulfovibrio desulfuricans was studied in a N-2-sparged reactor under agitation. Bacterial growth and product formation were monitored at 37 degrees C and pH 6.0-8.5 by measuring the time courses of the concentrations of free cells, substrates (lactate and sulfate), and products (acetate and total sulfide) in liquid medium and the amount of desorbed H2S. The experimental data were used to determine the stoichiometric relationships between substrate consumption and product formation. The batch rate data collected under a wide variety of medium pH’s and inoculum sizes were analyzed to determine kinetic and stoichiometric parameters for microbial sulfate reduction. The maximum specific growth rate was markedly dependent on the medium pH, whereas the growth yield practically remained unchanged over a pH range from 6.5 to 8.0. Predictions based on the theory of mass transfer with reaction indicated that there is essentially no H2S formation in the unmixed liquid region adjacent to the gas-liquid interface. This implies that the desorption of biogenic H2S is a physical mass transfer process without film reaction. The time variation of the measured amount of desorbed H2S was interpreted by using the developed kinetics of bacterial growth and subsequent H2S formation, the dissociation equilibria of dissolved H2S, and the mass transfer characteristics in the gas-sparged, stirred bioreactor.