Potencial de 10 isolados de Xanthomonas arborícola pv pruni para produção de xantana e otimização das condições de recuperação

Abstract

Microorganisms are capable of synthesizing a wide variety of chemical substances, such as the production of water-soluble biopolymers with different properties. The production of bacterial biopolymers can be induced by the excess of macronutrients, including limitation of other micronutrients, in addition to factors such as a species of microorganism, the conditions of the cultivation process and the use of prohibited substances for gum. In this context, the aim of the present work was to evaluate the production of xanthan, content of acetyl and pyruvate and the viscosity profile of gums from bacteria isolated in the city of Pelotas-RS in two different production methods, comparing with Xanthomonas campestris NRRL B-1459, which is industrially used to cause damage. Ten species of Xanthomonas arborícola pv pruni and Xanthomonas campestris NRRL B-1459 were used. For the production of xanthan biopolymers, MPI + II media (medium A) and MPII production medium (medium B) were used. For rheological analyses, 1% (w / v) solutions were prepared and a Rheostress rheometer (HAAKE RS 150) was used, varying the shear rate between 0.1 and 1000 s-1, for 300 s, at 25 ºC. The determination of acetic and pyruvic acid contents was performed using the hydroxamic acid and 2,4-dinitrophenylhydrazine methods, while the concentration values of xanthan and biomass were analyzed by gravimetric analysis. All experiments were carried out in triplicate. Mean values and standard deviations were submitted to analysis of variance and Tukey test. All Xanthomonas arborícola pv pruni strains isolated from peach trees from the city of Pelotas-RS have a great potential for xanthan production compared to the Xanthomonas campestris NRRL B - 1459 which is used industrially. Xanthan gum concentration in medium A ranged from 4.54 ± 0.44 g L-1 to 17.68 ± 2.14 g L-1, and in medium B from 8.12 ± 1.17 g L-1 to 26, 02 ± 0.18 g L-1. The values of piruvate contente varied from 0.33 ± 0.09% to 2.91 ± 0.49% in medium A and 0.37 ± 0.09% to 6.74 ± 0.63% in medium B, while the values of acetyl ranged from 0.30 ± 0.2% to 3.11 ± 0.10% in medium A, and in medium B from 0.33 ± 0.06% to 3.31 ± 0.05%. The viscosity profile of the xanthans in the aqueous solution showed a non-Newtonian, pseudoplastic behavior, typical for this type of gum.