Extração de biomoleculas em sistemas de duas fases aquosas convencionais e com polimeros termossensiveis

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

The semi-continuous and continuous extraction of a model enzyme, xylanase, in spray, sieve plates and packed columns were investigated using aqueous two-phase systems composed by polyethylene glycol (PEG) 4000 and potassium phosphate. For the spray column, the dispersed phase hold-up and overall mass transfer coefficients (Ko a) were evaluated for different superficial velocities of the dispersed phase (light phase). Resuhs indicated that an increase in superficial velocity in the range of O - 0.18 mmls of the dispersed phase had a positive effect on KD a and on hold-up in all colunm heights studied, 75, 161 and 246mm. For the sieve plate column, the effect ofthe superficial velocity ofthe dispersed phase and number of plates were also studied. Results showed that the KD a and hold-up increased with an increase in both parameters. The selectivity of separation of xylanase and BSA (model contaminant) was very high, since 60% of the enzyme was extracted in the light phase, whereas no significant amount of BSA was extracted. The possibility of using the sieve plate and packed column in continuous operations for enzyme extraction was studied. The influence of several kinds of packings, Raschig rings, glass spheres and polyestirene rings was studied as well as the superficial velocity ratio of the salt and PEG phases. The best selectivity was obtained with the polyestirene ring whith 94% of xylanase recovery in the polimeric phase and just 3% of contaminant was recovery to this phase. In a second part of this work a system composed by a thermoseparating hydrophobica11y modified polymers (HM-EOPO) has been used in one-polymer extraction systems, where the top phase is enriched by water and the bottom phase is enriched by the polymer (about 6-8%, w/w). The best separation ofDNA ftom plasmid was obtained using a low ionic system at pH 8 when the polymer is positively charged. By using salts that do not produce electrochemica1 driving force in the system contained HM-EOPO copolymer it is possible to distinguish other driving forces acting on the partitioning of biomolecules. One salt used in this study, K2S04, has this property. The partition coefficient of the proteins studied in this work, showed an independence of the pH of the system, but at extreme pH variation in K with the protein charge would indicate structural changes in the proteic molecule

ASSUNTO(S)

biomoleculas engenharia quimica extração (quimica) enzimas

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