Dynamic modeling and optimal fed-batch feeding strategies for a two-phase partitioning bioreactor

A dynamic model for the degradation of phenol in a two-phase partitioning b ioreactor has been developed based on mechanistic balances around the biore actor. The key process characteristics including substrate transfer between the organic and aqueous phases, substrate inhibition, oxygen limitation, a nd cell entrainment were incorporated into the model. The model predictions were validated against existing experimental data obtained for a 2-L biore actor, and good correlation was observed for the time frames of the simulat ions, as well as for trends in cell and substrate concentrations. Optimal f ed-batch, phenol feeding strategies were then developed based on two approa ches: (1) maximization of phenol consumption in a fixed time interval and ( 2) consumption of a fixed amount of phenol in minimal time. The optimal fee ding policies, determined using the Iterative Dynamic Programming algorithm , provided substantial improvements in the amount of phenol consumed when c ompared to a typical experimental heuristic approach. For example, 45.73 g of phenol was predicted to be consumed in 50 h (not including lag phase) us ing the optimal feeding profile compared to 10.26 g of phenol consumed in t he simulated experimental approach. Oxygen limitation was predicted to be a recurring operational challenge in the partitioning bioreactor, and had a strong impact on the optimization results. (C) 2000 John Wiley & Sons, Inc.