Diagramas de sistemas ternários formados por polímero ou copolímero tribloco, sal e água e partição de proteínas do soro do leite

• Autor(a) principal: Martins, João Paulo
• Data de Publicação: 2010
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/208
• topic: Sistemas aquosos bifásicos; Proteínas do soro do leite; Separação; Aqueous two phase system; Whey milk protein; Segregation; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::FISICO-QUIMICA

Phase diagrams of aqueous two phase system formed by polymer or copolymer + salt (organic or inorganic) + water were determined in various temperatures. Aqueous two phase systems composed by Poly(ethylene glycol) 400 g.mol1+ sodium sulfate or magnesium sulfate were determined at (298.2, 308.2and 318.2)K. The systems formed by poly(ethylene glycol) 6000 g.mol1 + lithium sulfate, sodium sulfate, magnesium sulfate or zinc sulfate were determined at (283.2, 298.2 and 313.2) K. The temperature effect on the binodal position was not significant, indicating a small enthalpic contribution associating to the phase segregation. The ability of three salts in inducing the formation of the biphasic system with PEO 6000 or PEO 400 (MgSO4>Na2SO4) the followed the order ZnSO4>MgSO4>Na2SO4>Li2SO4. An increase of molecular weight causes an increase of biphasic area. The systems formed by copolymer were determined using a F68 or L35 triblock copolymer. The aqueous twophase systems composed by triblock copolymer, F68 (8460 g mol−1) + sodium sulfate, lithium sulfate, zinc sulfate or ammonium sulfate were determined at (278.2, 288.2 and 298.2) K. The ability of these four salts in inducing the formation of the ATPS with F68 follows the order: sodium sulfate > zinc sulfate > ammonium sulfate > lithium sulfate. The triblock copolymer L35 was used to build phase diagrams composed by L35 (1900 g.mol1) + sodium tartarate, sodium citrate or sodium nitrate at (283.2, 298.2 and 313.2) K. The ability of three salts in inducing the formation of the biphasic system with L35 follows the order sodium citrate > sodium tartarate > sodium nitrate. The temperature effect on the position of the binodal curves was not relevant, indicating a small enthalpic contribution associating to the phase separation. However, an increase of temperature causes an increase of slope of tie line indicating water transference to the top phase from bottom phase. The partitioning coefficients for αlactoalbumin and βlactoglobulin were investigated as a function of electrolyte nature (cation effect), tie line length (TLL) and molar mass of polymer. The systems used for the partitioning study were: PEO 6000 + MgSO4, Na2SO4 or Li2SO4 and PEO 1500 + MgSO4, Na2SO4 or Li2SO4 at 298,2K. The αlactoalbumin has larger partition coefficients as compared with the βlactoglobulin in all ATPS studied. A strong dependence of the electrolyte nature (cation effect) was observed. The partitioning coefficient for both proteins in the system formed by PEG 1500 follows the order: Li2SO4 > Na2SO4 > MgSO4. For the systems formed by PEO 6000 the order, with an increase of TLL, for both proteins were: Li2SO4 > MgSO4 > Na2SO4. An increase of molecular weight of polymer causes a decrease of partition coefficient of αlactoalbumin, excepted for the magnesium salt. Don t was observed a significant effect of molecular weight for the βlactoglobulin, excepted for the magnesium salt.