Simulation of xanthan gum production by a chemically structured kinetic model Original Research Article

A chemically structured kinetic model for xanthan production is proposed. Both carbon and nitrogen source metabolisms into cells are taken into account by the model. A kinetic reaction network is proposed, using lumping of several compounds into groups for a simplification of the metabolic pathways. Seven reactions are taken into account in the simplified reaction network, involving 11 different species; kinetic equations of Monod type for the reactions involved in the network considered are assumed. A stoichiometric study yields seven key components, the kinetic model is formulated as a set of differential equations formed by the production rates of the seven key components (six equations only if the pseudo-steady state is assumed for ATP), while the evolution of the other components involved in the reaction network are derived. Simulations of different cases in a stirrer tank bioreactor have been made, using a linear increase of stirrer speed, at different dissolved oxygen concentrations and with several initial nitrogen concentrations. The model is able to simulate the system evolution under different operational conditions, predicting an optimum value for the initial nitrogen concentration.