Economic Improvement of Continuous Biochemical Reactors via Multi-feed Operation

The production of pharmaceuticals, a multi-billion dollar worldwide industry, is expected to see large economic growth in the coming years. However, stagnation in the development of new products has led the industry to search for other methods to achieve these economic goals. The change from batch processing practices to the continuous production seen in commodity chemicals industries is a way of mitigating operating costs and increasing revenue. The optimal operation of single feed continuous bioreactors has been extensively studied, but these systems are not adaptable to the changing needs of biochemical systems as they only allow a single feed concentration. In addition, some biological systems are capable of utilizing multiple substrates, opening the door to potential cost savings not possible in single feed systems. In this work, the optimal operation of a multi-feed bioreactor is investigated to allow for the potential use of multiple substrates while independently varying the dilution rate and inlet substrate concentrations. The production of β-carotene from a glucose and ethanol substrate is used as a case study, where it is shown that the use of a multi-feed bioreactor has the potential to provide a near 30% economic improvement in operating costs despite a 23% decrease in the bioreactor productivity. These economic improvements are linked to an increase in cellular and substrate yield of the product achieved with the addition of a secondary substrate.