Experimental Evaluation of Batch and Continuous Production of Baker’s Yeast under Computer Controlled pH

Steady state and dynamic fermentations of baker's yeast in molasses based media were analyzed in a laboratory scale bioreactor. Sugar and biomass balances together with the Monod biokinetics were used to develop the process model. Parameters of the model were obtained using collected experimental data. Model predicted open loop responses to step changes in feed concentration as well as dilution rate were compared with experimental data and a good agreement was observed. Despite the nonlinear nature of pH in a biological system, it was controlled successfully using a special on-off strategy implemented on a personal computer. Results proved that productivity of the continuous process was at least twice that of the batch process.