Metabolic structured kinetic model for xanthan production

Abstract

A metabolic structured kinetic model for xanthan gum production is described and fitted to experimental data obtained in a batch stirred tank reactor. The model is able to describe the evolution of biomass, consumption of carbon, nitrogen, dissolved oxygen, and production of xanthan at different temperatures. The description of growth is carried out by means of an unstructured model taking the nitrogen source as the limiting nutrient, employing the logistic equation which fits adequately the experimental data of the increase in biomass concentration as a function of initial concentrations of biomass and nitrogen source. The model proposed is metabolically structured because it takes into account the carbon source metabolism into the cell, describing xanthan production, carbon source, and dissolved oxygen consumption in a structured way according to a reaction network as a simplified scheme of the intracellular metabolism. The limiting nutrient of xanthan production and carbon source consumption is supposed to be dissolved oxygen. The parameter estimation has been performed by fitting to experimental data, employing an integral method coupling a fourth-order Runge-Kutta algorithm to a multiple-response nonlinear regression technique. Runs performed at four different temperatures (25, 28, 31, and 34°C) are fitted and described by the model.