The dissolved oxygen concentration (DO) is an important variable in aerobic fermentations. Precise control of the DO is critical in fermentation processes for the investigation of the best conditions for secondary product formation. Oxygen limitation conditions have been known to enhance the synthesis of secondary products. An adaptive pole placement control that maintains a constant sheer environment is applied to Bacillus subtilis fermentation for the production of -lactamase. AutoRegressive eXogeneous (ARX) input models are used for the control, and supervision and coordination techniques are applied to improve the control performance. The effect of DO level on the productivity of -lactamase under oxygen-limited conditions is assessed.

Modeling of the equilibrium in aqueous two-phase systems (A2PS) is very important for modeling the partition behavior of molecules in A2PS. Also, the study of process improvement can be made easier by the equilibrium modeling when the production and separation is combined into one stage. Flory−Huggins is a simple model and can be used for equilibrium calculations. This paper focuses on the numerical problems associated with the thermodynamic equilibrium formulation and attempts to show the effect that the proper scaling and optimization objective function has on the accuracy of the solution.

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