Model-Based Analysis of a Phenol Bio-Oxidation Process by Adhered and Suspended Candida tropicalis

Phenol is an important commodity for the chemical industry, used for many processes and deemed to be a major pollutant due to its xenobiotic nature and high toxicity. For the purpose of phenol bioremediation a biotechnological set up consisting of a continuous packed column bioreactor with Candida tropicalis adhered onto activated carbon beads has been previously described. In this work, we show how the integration of available experimental data of such a biotechnological set up into a mathematical model, can lead both to a better comprehension of the underlying physiological mechanisms operating in the cell culture, and to the identification of the system parameters optimum performance. The model so constructed describes the dynamics of phenol uptake and growth rates by the adhered and suspended biomass; the lethality rates; the adhered biomass removal into suspension or adherence onto carbon beads rates and the phenol and biomass (adhered and suspended) concentrations. It also serves to identify different physiological states for the adhered and the suspended biomass; its predictions being verified by comparing with experimental observations. Based on the model description, different optimization strategies are proposed, some of which have been experimentally tested, encompassing changes in bioreactor operation conditions, process development and strain development.