Detalhes bibliográficos
| Ano de defesa: |
2007 |
| Autor(a) principal: |
Borges, Caroline Dellinghausen |
| Orientador(a): |
Vendruscolo, Claire Tondo |
| Banca de defesa: |
Não Informado pela instituição |
| Tipo de documento: |
Tese
|
| Tipo de acesso: |
Acesso aberto |
| Idioma: |
por |
| Instituição de defesa: |
Universidade Federal de Pelotas
|
| Programa de Pós-Graduação: |
Programa de Pós-Graduação em Biotecnologia
|
| Departamento: |
Biotecnologia
|
| País: |
BR
|
| Palavras-chave em Português: |
|
| Palavras-chave em Inglês: |
|
| Área do conhecimento CNPq: |
|
| Link de acesso: |
http://guaiaca.ufpel.edu.br/handle/123456789/1248
|
Resumo: |
Xanthan yield and physical and chemical characteristics can be improved by modification in culture conditions, as well as, by post-fermentation treatments in order to obtain a xanthan with the required characteristics. The aim of this work was to study the operational conditions in xanthan production by Xanthomonas arborícola pv pruni strains 106 and 115 to be used in oilwell drilling fluids. The influence of thermal treatment applied to the fermentation broth was evaluated in the xanthan produced by strain 106 in a range of pH and stirrer speed. The thermal treatment decreased the yield between 5.8 and 14%, nevertheless, was observed increase of aqueous solution and fermentation broth viscosities. The aggregation of xanthan molecules caused by thermal treatment and determined by increase of molar mass was dependent on the sodium content. As a result, a correlation between molar mass and xanthan solution viscosity can be observed. The fermentation broth sterilization was adopted for experiment in which a pre-selection of production medium in orbital shaker was performed for subsequent pH, production medium and stirrer speed study in fermentor by strains 106 and 115. Xanthan production and viscosity was dependent on the strain of X. arborícola pv pruni and on the operational condition used. The production medium B showed the best balance of yield and viscosity results, in orbital shaker, as well as in fermentor. The best results for both strains were obtained at pH 7, 600 rpm and 66 h of fermentation. The two strains showed potential for xanthan production. In an evaluation study of, physical and chemical characteristics, the xanthan produced by strain 115 was compared to the characteristics of the commercial xanthans, Roeper and Kelzan. The former is for application in food, pharmeceutical products and cosmetics and the latter for application in oilwell drilling fluids. The results were within the literature specified patterns, except by the low piruvate content of xanthan produced by strain 115, low monovalent salt content of Roeper sample and high divalent salt content of both commercial samples. The xanthans produced by X. arborícola pv pruni were evaluated as viscosifying fluid for use in oilwell drilling, in comparison to Duo Vis, Kelzan and Xanvis commercial brands. As a whole, the results obtained in this study show that the commercial polymers are more efficient when used in aqueous solution, since these polymers contain high salt concentrations. Xanthans produced by patovar pruni, Xc 106 600 and Xc 115 600, as having low salt concentration, they show potential for application in oilwell drilling fluid, when a salt solution was used, similar to the conditions of marine exploration. |
