Caracterização da goma xantana em função da cepa de Xanthomonas campestris pv pruni e das condições operacionais

Abstract

Was characterized the xanthan gum synthesized by thirty strains of Xanthomonas campestris pv pruni, and in different operational conditions. The biopolymer was produced in orbital shaker in 50mL flask, afterwards was evaluated the production, apparent viscosity and the chemical composition of the produced biopolymers. The results of production, viscosity and quantitative chemical composition are dependents of strains. The aqueous solutions 3% (m/v) of the xanthans produced by the 29 strains showed pseudoplastic behavior. The xanthans synthesized by the 29 strains showed rhamnose, mannose, glucose and glucuronic acid in its chemical composition, however, with quantity diferences. Amongst the thirty strains, the 101 was selected in function of its results for transposition of scale of production of 3L in fermentor. Was evaluated production, viscosity and chemical composition of the biopolymers; pH, oxygen transfer coefficient (kLa) and the cellular mass dry of the medium, in two combinations of agitation speeds and aeration rate (condition: 300rpm; 3vvm and condition B: 200rpm; 2vvm) and in different times of fermentation. The production in the condition A was higher than condition B, except in 48h. The results of cellular mass dry were similar in the two treatments, differing only in 66h. The decrease of pH was similar for both conditions (A and B) with the to elapse of the time. The aqueous solutions of the xanthans synthesized under the two conditions (A and B), in the different times, showed pseudoplastic behavior. The apparent viscosity of the xanthans synthesized in the condition A was higher in all the fermentation times. In the condition A, the kLa was higher condition B, demonstrating that the higher concentration of oxygen dissolved in the condition A favored the production of xanthan and apparent viscosity. All the samples contained the same sugars and acid detected in the xanthans produced in scale of 50mL. Until 54h, did not have difference in the chromatographic profile of the samples, between the treatments; from 66h the content of mannose decreased, in both treatments and increased the amount of glucose in condition B. The best results of production and viscosities were obtained in the condition of higher speed of agitation and aeration rate. Herewith was considered, for this strain, the use of the condition A, with ending of the fermentation in 54h, when was reached the best combination enters the results of viscosity and production, with lesser expense of energy and time.