Resumo

INTRODUCION: The xanthan gum is an exopolysaccharide from bacteria of the genus Xanthomonas that can be used as thickener, stabilizer, fat substitute, biofilms production and drilling fluid of oil wells. The evaluation of Xanthomonas spp production can be performed with previously isolated strains, in particular means for designating, in that substrate, the best producer microorganism xanthan gum. MATERIAL AND METHODS: In this work was used three strain of the Xanthomonas (Xanthomonas axonopodis pv manihotis IBSBF 290, Xanthomonas campestris pv campestris IBSBF 472, Xanthomonas sp S6) obtained from the Culture Collection of the Biomaterials Laboratory / Institute Technology and Research (LBMat/ITP). The inoculum was prepared using Erlenmeyer flasks of total volume of 125 mL containing 14 mL of YM medium, inoculed with 1 mL of solution (one scope of microorganism to 2 mL of YM medium) and incubated at 28°C and 100 rpm for 24h in an orbital shaker. These cultures were used as innoculum for 250 mL Erlenmeyers containing 85 mL of production medium and incubated at 28°C and 180 rpm for 96h in an orbital shaker. The fermentation medium ranged in concentration of the carbon source, sucrose, magnesium sulphate heptahydrate (MgSO4.7H2O) and dibasic potassium phosphate (K2HPO4). A Central Composite Design (CCD) 23 with five replications on central point was carried out for defining the concentrations of MgSO4.7H2O, K2HPO4, and sucrose. RESULTS AND DISCUSSION: Xanthan gum obtained from the soluble supernatant from each experimental condition was determined gravimetrically by dry weight after precipitation with ethanol, and the results were used as response variables to experimental design respective. The influence of sucrose, MgSO4.7H2O and K2HPO4 concentrations were analyzed with statistical study for the three strains. It was observed significant effect (p < 0.05) on the response when used the variable concentration of K2HPO4 for Xanthomonas 290 and 472, as well as was also observed significant effect (p < 0.05) on the response when used the variable concentration of MgSO4.7H2O for Xanthomonas S6. CONCLUSION: An increase on the concentration of these salts on the medium, depending on the strain used, can then improve the xanthan gum production. Acknowledgements: CNPq, CAPES, and FAPITEC/SE for their financial support