Sistemas aquosos bifásicos: determinação de equilíbrio de fase e aplicação para partição de alfa-lactoalbumina e beta-lactoglobulina
Loading...
Date
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Universidade Federal de Viçosa
Abstract
Este trabalho apresenta, no primeiro capítulo, uma breve revisão sobre obtenção do soro do leite e sua composição, destacando as propriedades nutricionais e tecnológicas das proteínas do soro. Posteriormente, aborda os principais métodos de separação das proteínas do soro, apresentando a utilização de sistemas aquosos bifásicos (SABs) como uma técnica eficiente e economicamente viável de extração líquido-líquido para separação das proteínas α-lactoalbumina (α-la) e β-lactoglobulina (β-lg). O segundo capítulo descreve a obtenção e a determinação do equilíbrio de fase de novos SABs constituídos pelo copolímero L64 + sais orgânicos (citrato de amônio, citrato de sódio, succinato de sódio ou tartarato de sódio) + H2O em diferentes temperaturas (5, 15 e 25 °C). Medidas microcalorimétricas mostraram que o processo de separação de fases nestes sistemas foi exotérmico e o sal citrato de sódio (Na3C6H5O7) foi mais efetivo em promover a separação de fases que o sal citrato de amônio ((NH4)3C6H5O7). A capacidade dos diferentes ânions em induzir a formação de SABs com L64 obedeceu à seguinte ordem: citrato (C6H5O73–) > tartarato (C4H4O62–) > succinato (C4H4O42–). Por fim, o terceiro capítulo aborda uma aplicação dos SABs constituídos pelo polímero PEO 1500 + sais orgânicos (citrato de sódio, succinato de sódio ou tartarato de sódio) + H2O para a partição das proteínas α-la e β-lg. Além disso, os parâmetros termodinâmicos (ΔtrH°, ΔtrS° e ΔtrG°) associados à transferência das proteínas da fase inferior (FI) para a fase superior (FS) dos sistemas foram determinados. Os resultados obtidos mostraram que a partição da FI para FS é termodinamicamente favorável para α-la (- 6,61 < ΔtrG° < - 0,77 kJ mol-1), mas é desfavorável para β-lg (2,68 < ΔtrG° < 6,20 kJ mol-1). Além
disso, este processo ocorre com perda de entropia configuracional (- 9,23 < TΔtrS° < - 1,34 kJ mol-1) e as interações intermoleculares entre moléculas de proteína e polietilenoglicol são mais favoráveis que as interações intermoleculares entre moléculas de proteína e sal (- 7,95 < ΔtrH° < - 1,42 kJ mol-1), para ambas as proteínas em todos os SABs estudados. Para explicar o comportamento de partição das proteínas, o modelo derivado da teoria de Flory-Huggins foi utilizado e observou-se que a partição da α-la para a FS foi entalpicamente dirigida, enquanto a partição da β-lg para a FI foi entropicamente dirigida.
This work presents, in its first chapter, a brief review on production and compositions of cheese whey, emphasizing the nutritional and technological properties of whey proteins. Subsequently, the main methods of separation of whey proteins are addressed, using aqueous two-phase systems (ATPS) as an efficient and economically viable liquid-liquid extraction technique for separation of alpha-lactalbumin (α-la) and beta-lactoglobulin (β-lg) proteins. The second chapter describes the formation and determination of the phase equilibrium of new ATPS formed by copolymer L64 + organics salts (ammonium citrate, sodium citrate, sodium succinate or sodium tartrate) + H2O at different temperatures (278.15, 288.15 and 298.15 K). Microcalorimetric measurements showed that the phase separation process in these systems was exothermic and the salt sodium citrate (Na3C6H5O7) was more effective in promoting phase separation than ammonium citrate ((NH4)3C6H5O7). The capacity of the different anions in inducing ATPS formation with L64 followed the order: citrate (C6H5O73–) > tartrate (C4H4O62–) > succinate (C4H4O42–). Finally, the third chapter describes an application of ATPS formed by polymer PEO 1500 + organics salts (sodium citrate, sodium succinate or sodium tartrate) + H2O for partition of α-la and β-lg proteins. In addition the thermodynamical parameters (ΔtrH°, ΔtrS° e ΔtrG°) associated with protein transfer from the bottom phase (BP) to the top phase (TP) were determined. The results showed that the partition from BP to TP is thermodynamically favorable to α-la (- 6.61 < ΔtrG° < - 0.77 kJ mol-1), but is unfavorable for β-lg (2.68 < ΔtrG° < 6.20 kJ mol-1). Additionally, this process occurs with loss of configurational entropy (- 9.23 < TΔtrS° < - 1.34 kJ mol-1) and the intermolecular interactions between proteins and poly(ethylene glycol) molecules are more favorable than intermolecular interactions between proteins and salt molecules (-7.95 < ΔtrH° < -1.42 kJ mol-1) for both proteins in all ATPS studied. To explain the partition behavior of α-la and β-lg the model derived from the Flory-Huggins theory was used and it was observed that α-la partition to the TP was enthalpically driven, while the β-lg partition to the BP was entropically driven.
This work presents, in its first chapter, a brief review on production and compositions of cheese whey, emphasizing the nutritional and technological properties of whey proteins. Subsequently, the main methods of separation of whey proteins are addressed, using aqueous two-phase systems (ATPS) as an efficient and economically viable liquid-liquid extraction technique for separation of alpha-lactalbumin (α-la) and beta-lactoglobulin (β-lg) proteins. The second chapter describes the formation and determination of the phase equilibrium of new ATPS formed by copolymer L64 + organics salts (ammonium citrate, sodium citrate, sodium succinate or sodium tartrate) + H2O at different temperatures (278.15, 288.15 and 298.15 K). Microcalorimetric measurements showed that the phase separation process in these systems was exothermic and the salt sodium citrate (Na3C6H5O7) was more effective in promoting phase separation than ammonium citrate ((NH4)3C6H5O7). The capacity of the different anions in inducing ATPS formation with L64 followed the order: citrate (C6H5O73–) > tartrate (C4H4O62–) > succinate (C4H4O42–). Finally, the third chapter describes an application of ATPS formed by polymer PEO 1500 + organics salts (sodium citrate, sodium succinate or sodium tartrate) + H2O for partition of α-la and β-lg proteins. In addition the thermodynamical parameters (ΔtrH°, ΔtrS° e ΔtrG°) associated with protein transfer from the bottom phase (BP) to the top phase (TP) were determined. The results showed that the partition from BP to TP is thermodynamically favorable to α-la (- 6.61 < ΔtrG° < - 0.77 kJ mol-1), but is unfavorable for β-lg (2.68 < ΔtrG° < 6.20 kJ mol-1). Additionally, this process occurs with loss of configurational entropy (- 9.23 < TΔtrS° < - 1.34 kJ mol-1) and the intermolecular interactions between proteins and poly(ethylene glycol) molecules are more favorable than intermolecular interactions between proteins and salt molecules (-7.95 < ΔtrH° < -1.42 kJ mol-1) for both proteins in all ATPS studied. To explain the partition behavior of α-la and β-lg the model derived from the Flory-Huggins theory was used and it was observed that α-la partition to the TP was enthalpically driven, while the β-lg partition to the BP was entropically driven.
Description
Citation
ANDRADE, Vivianne Molica de. Aqueous two-phase systems: determination of phase equilibrium and application for partition of alpha-lactoalbumin and beta-lactoglobulin. 2011. 77 f. Dissertação (Mestrado em Agroquímica analítica; Agroquímica inorgânica e Físico-química; Agroquímica orgânica) - Universidade Federal de Viçosa, Viçosa, 2011.