Stability and response analyses of phenol degrading biochemical systems

Abstract

Chemical systems having non-linear dynamic state equation exhibit unusual behaviour like multiplicity, sustained oscillations etc., when perturbation in any forcing function is somehow introduced to an existing steady state. Under this situation a reacting system may exhibit one or more ambiguous steady states. Biochemical systems using microorganisms following either substrate- or product-inhibited growth kinetics are usually characterized with this type of behaviour. In the present investigation biodegradation of phenol using Pseudomonas putida following substrate inhibited growth kinetics has been taken as model system. The system has been studied in a 2 dm³ B. Braun fermenter in batch and continuous modes of operation separately. Using the experimental data obtained in batch mode of operation the kinetic parameters of the systems have been determined considering substrate inhibited Haldane type kinetics for biodegradation of phenol. Two separate techniques, viz., linear stability analysis and phase plane analysis have been performed to study the characteristics of steady states from local and global points of view respectively. Response analysis of the system has been performed using step-type perturbations in inlet substrate concentrations of different amplitudes. The experimental findings show good agreement with the simulated results.