Determinação de parâmetros fermentativos utilizando diferentes impelidores na produção de goma xantana pela bactéria Xanthomonas campestris para aplicações cosméticas

Abstract

Xanthan gum is an exopolysaccharide of microbial origin obtained by the bacterium Xanthomonas campestris from fermentation process. This gum has several applicability in the food, petroleum and cosmetic areas, being used as a thickener, stabilizer and/or emulsifier, standing out compared to raw materials with similar functions because it is of biotechnological origin, does not require high amounts to be active, in addition to the its production to be independent of seasonal conditions. Although the xanthan gum production process has already been much discussed in the literature, parameters such as the volumetric mass transfer coefficient (kLa) and mixing time (tm) have not yet been addressed for the production of this biopolymer by Xanthomonas campestris. In this sense, the objective of this work was to determine the kLa and tm parameters using different sets of impellers (Rushton-Rushton, Rushton-Inclinada and Rushton-Elefante) in a STR reactor, against colloidal dispersions of xanthan gum with concentrations ranging from 0.10% to 0.85% (m.v-1), in order to simulate the fermentation process and thus determine which of the sets would work best under conditions of high viscosity. For this, the kLa was determined by the dynamic method and the mixing time by means of the pH probe response. Both tests were conducted at stirring speeds of 200 and 600 rpm. Better results were obtained for Rushton-Elefante type impellers, with relevant mass transfer and mixing profiles at high concentrations. This model was then used for fermentation, which was carried out at a temperature of 28°C, with stirring at 300 rpm and aeration at 1 vvm in the first 24 hours; in the remaining 48 hours, 750 rpm and 1.2 vvm were used. After fermentation, a productivity of 0.26 g.L-1.h-1 was obtained, twice the value reported in the literature under conditions of supplementation and similar fermentation parameters, which suggests that the parameters used may favor this process. A profile observed for xanthan gum during the process was buffering action in an acid medium and although this result has not yet been reported in the literature, if validated it may present a new path for research in cosmetic lines, especially because this active is presented as a substitute interesting for formulations containing acrylate. Therefore, it is recommended that future studies be conducted to validate this hypothesis.