SIMULATION OF XANTHAN GUM PRODUCTION BY A CHEMICALLY STRUCTURED KINETIC-MODEL

A chemically structured kinetic model for xanthan production is propos ed. Both carbon and nitrogen source metabolisms into cells are taken i nto account by the model. A kinetic reaction network is proposed, usin g lumping of several compounds into groups for a simplification of the metabolic pathways. Seven reactions are taken into account in the sim plified reaction network, involving 11 different species; kinetic equa tions of Monod type for the reactions involved in the network consider ed are assumed. A stoichiometric study yields seven key components, th e kinetic model is formulated as a set of differential equations forme d by the production rates of the seven key components (six equations o nly if the pseudo-steady state is assumed for ATP), while the evolutio n of the other components involved in the reaction network are derived . Simulations of different cases in a stirrer tank bioreactor have bee n made, using a linear increase of stirrer speed, at different dissolv ed oxygen concentrations and with several initial nitrogen concentrati ons. The model is able to simulate the system evolution under differen t operational conditions, predicting an optimum value for the initial nitrogen concentration.