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|Title:||Caracterização de um novo sistema bifasico aquoso e aplicação em extração de proteinas com coluna de discos perfurados rotativos|
|Author:||Sarubbo, Leonie Asfora|
|Abstract:||Resumo: A partição bifásica aquosa explora a capacidade exibida por soluções de dois polimeros ou de um polímero e um sal de se separarem em duas fases aquosas sempre que certas concentrações mínimas sejam excedidas. As duas fases aquosas assim formadas diferem na sua composição, sendo cada uma delas rica num dos constituintes do sistema, isto é, os dois polimeros ou o polimero e o sal concentram-se em fases distintas. Estas fases apresentam elevados teores em água, podendo em alguns casos atingir valores superiores a 90 %, constituindo ambientes suaves para moléculas e partículas biológicas. O objetivo principal deste trabalho residiu na caracterização do sistema bifásico aquoso formado por um polímero típico do Nordeste brasileiro, o polissacarídeo do cajueiro (Policaju). Sendo o elevado custo dos polímeros envolvidos o principal entrave à aplicação em grande escala da partição bifásica aquosa, este sistema apresentou a possibilidade em reduzir este custo, aumentando a competitividade da partição bifásica aquosa como processo alternativo frente aos processos tradicionais de recuperação de bioprodutos. Mostrou-se ao longo desta tese que o sistema testado apresentou propriedades fisicas (razão e tempo de separação de fases, densidade, viscosidade) e de partição características de sistemas bifásicos aquosos polímero-polímero. Após o isolamento do polissacarídeo, determinouse o diagrama de fases e estudou-se a partição de uma proteína modelo, a albumina de soro bovino. Verificou-se o efeito exercido pelas variáveis do sistema, peso molecular do PEG (1500, 4000|
Abstract: Aqueous two-phase partition explores the possibility of solutions of two polymers or one polymer and one salt separating into two immiscible aqueous phases, when certain critical concentrations are exceeded. Each one of these aqueous phases is more concentrated in one of the phase forming chemicals. Both exhibit a high water content, in some cases as much as 90%. Due to this high water content, these byphasic systems provide a gentle environment for molecules and partic1es with biological activity. The main subject ofthis work was the characterisation of a new aqueous two-phase system based on a typical Brazilian north-westem polymer, the polysaccharide of cashew tree (Policaju). Since the cost of the phase forming polymers is the main drawback on the large scale application of aqueous two-phase partition, this system showed the possibility of decreasing this cost by increasing the applicability of biphasic partition as an alternative technique to the traditional recovery processes ofbioproducts. It is shown tOOt physical properties (phase volume ratio, time for phase separation, density, viscosity) and partition properties of the tested system are similar to others aqueous two-phase polymer-polymer systems. Afier the polysaccharide isolation, the phase diagram was determinate and the partition of a model protein, bovine serum albumin, studied. It was analysed the effect of PEG molecular weight (1500, 4000 and 8000), polymer concentration, temperature (25°C e 40°C), pH (6,0, 7,0 and 8,0) and NaCI (O,lM e 1M) addition. It was observed a displacement ofthe binodal towards lower polymer concentrations when PEG molecular weights decreased. Conversely, the variation of pH and temperature did not promote significant alterations on the binodal. It was not possible to stabilise a relation between the protein partition coeflicient and the PEG molecular weight, whi1e the increase in tie-line length and temperature and the decrease in pH promoted the decrease of the partition coeflicient. The results obtained for NaCI addition showed a tendency for the decrease ofthe partition coeflicient with the increase of salt concentration, although in some cases, the partition coefficient decreased on1y for a determina te salt concentration, depending on the system and pH. Continuous operation with aqueous two-phase systems was also tested. The beOOviour of the biphasic system PEG-Policaju was studied using a perforated rotating disc contactor (pRDC). The transfer of bovine serum albumin ftom the dispersed phase to the continuous phase was studied by using the PEG4000-Policaju system selected ftom batch extraction. The column was operated in countercurrent and in a continuous mode during 55 minutes of operatio_ where the dispersed phase was constituted by the PEG-rich phase and the continuous phase by the Policajurich phase. Variations in the rotation velocity (60, 140 and 220 rpm), dispersed phase velocity (2, 3 and 5 rnL/min) and discs number (03 and 04) were investigated. The performance of the equipment was characterised by the ana1ysis ofthe ftactional dispersed phase holdup, mass transfer coefticient and KA W ASE recuperation indices. The results showed an increase ofthe dispersed phase holdup, mass transfer coeflicient and recuperation indices with the increase of the rotation velocity. The same effects were observed for the increase of the dispersed phase velocity, except for the recuperation indices, which did not show a regular tendency. The increase of system composition decreased the ftactional dispersed phase holdup and the mass transfer coeflicient, although did not show a significant effect over the recuperation indices. The number discs variation did not demonstrate a significant effect upon the ftactional dispersed phase holdup, although the mass transfer coeflicient and the recuperation indices were higher for 03 discs. The ana1ysis of bovine serum albumin continuous extraction showed the higher protein transfer for the following conditions: 9%PEG4000-18%Policaju system in PRDC with 03 rotary discs with rotation velocity of 220 rpm and dispersed phase velocity of 2 mL/min. The economic ana1ysis showed that PEG-Policaju aqueous two-phase system is very competitive with other polymer-polymer systems described in the literature. This permits the development offuture researches with this new system in recovery processes
|Subject:||Extração por solventes|
|Appears in Collections:||FEQ - Dissertação e Tese|
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