99A-18 |
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F. PADILHA1, Y. Rosato2, and A. Scamparini2. (1) Food Engineering, URI Campus de Erechim, CEP 99700-000, Erechim, Brazil, (2) Food Science, UNICAMP, P.O. Box 13081, Campinas, Brazil The cellular production of a typical bacterial exopolysaccharide is a compelx process involving nucleotide-sugar substrates, sugar-specific glycosyl transferases, modification enzymes, polymerases, and membrane-associated proteins and cofactors. This complexity and our relative ignorance of the molecular events that are involved has made it difficult to genetically manipulate the EPS-producing bacteria in order to alter culture conditions, to introduce new production microorganisms, or to change the EPS structures. In this report we describe the transfer of several genes from Zymomonas mobilis into a different genus, Xanthomonas, not only to produce xanthan gum, but to produce the new EPS with association of the levan gum. The objective of this work was to evaluate the production and to characterize this biopolymer, to verify the influence of the addition of genes involved in the gum production in a Xanthomonas strain. The bacterium used was electrotransformated using a plasmid with genes for the synthesis of the gum. After the transformation, the medium YM was used for bacterial growth and the medium MPI and II was used for the production of the biopolymer. Bacterial cells were grown at 28ºC, 200 rpm, pH 7.0. The rheology of the fermentation broth was analyzed by apparent viscosity and the polymer was recovered with ethanol (1:3, v/v). After its recovery, the productivity evaluation was performed. The chemical analysis was conducted by HPLC and GC-MS for the identification of the monosaccharides present. The viscosity analysis was performed for aqueous solutions 3%, 25ºC. Measurements were performed using a parallel plate geometry PQ45 in rheometer Haake model CV-20. The polysaccharide from the recombinant microorganisms largely indistinguishable, structurally and functionally, from native levan gum. The chromatographic analysis showed the different composition of monosaccharides for the polymers. Rheological behavior was observed for xanthan gum, levan gum and new EPS solutions. The physical tests confirmed that the EPS secreted by the recombinant Xanthomonas strains was largely indistinguishable from authentic xanthan and levam gum.
Session 99A, Biotechnology: General
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