Xanthan gum production: An unstructured kinetic model

Abstract

Xanthan production was studied in a stirred-tank fementor and modeled using unstructured kinetic models. First, the influences of the operational conditions have been studied. Temperature (between 22 and 34°C), aeration (changing stirrer speed between 150 and 1,000 rpm, maintained at constant or varied through fermentation time), and the pH control (with two alkalis) were analyzed. Then, unstructured kinetic models proposed in the literature for this system were reviewed and applied. These models have been checked to describe the experimental results, calculating the parameters by nonlinear regression. The results show that these models do not take into account all the necessary nutrients, which are carbon source, nitrogen source, and dissolved oxygen. Afterward, an unstructured kinetic model describing biomass, carbon source, nitrogen source, and dissolved oxygen evolutions was proposed and applied. Parameters estimation were carried out by means of both differential and integral methods. Parameters values were finally obtained applying an integral method using non-linear regression techniques. The model proposed in this work is composed of five differential equations with production rates of the five components taken into account: biomass, carbon, and nitrogen sources, xanthan, and dissolved oxygen, capable of fitting all the three experiments considered, at different temperatures and controlling and not controlling pH.