This paper deals with the study of the kinetics of batch fermentations for a sensitive strain of S. cerevisiae growing in a culture medium containing K2 killer protein. The inhibition due to the killer toxin was measured by the reduction of the viable biomass, ethanol production and glucose consumption compared with a reference fermentation. The reference culture was run under the same conditions, but using a heat-denatured solution of killer protein. Results showed a decrease of the viable population of 67.8% after 15 h incubation. The fermentation time for the total consumption of the glucose was significantly affected by the presence of the killer toxin. The specific rate of ethanol production was also affected during the fermentation. However, the yields of ethanol and biomass were very similar for both fermentations. A kinetic mathematical model was proposed to explain the dynamics of the S. cerevisiae 522D growth in the presence of the K2 killer protein. The results of the suggested simulation were in agreement with the experimental data.