Luciana Alves de Oliveira

Partition of trypsin in aqueous two-phase systems of poly(ethylene glycol) and cashew-nut tree gum

Abstract The partition behaviour of trypsin in poly(ethylene glycol) (PEG)–cashew-nut tree gum aqueous two-phase systems has been characterized. The enzyme partitioned preferentially into the cashew-nut tree gum phase. Investigation on the effect of the molecular weight of the PEG, the pH of system and the tie-line length of the biphasic diagram lead to the conclusion that the system properties had little effect on trypsin partition coefficients. In some cases, the NaCl addition changed dramatically the partition coefficient, this means that altering the conditions allows the manipulation of the protein partition. Maximum recovery of trypsin activity in the cashew-nut tree gum phase was obtained with PEG (molecular weight 8000) at pH 7.0 and 1.0 M NaCl.

New aqueous two-phase system based on cashew-nut tree gum and poly(ethylene glycol).

The characterisation of a new system based on cashew-nut tree gum, a branched acidic heteropolysaccharide found in Brazil, and poly(ethylene glycol) (PEG) was studied. Phase diagrams are provided for the PEG-cashew-nut tree gum system. The influence of PEG molecular mass, tie-line length and pH on bovine serum albumin (BSA) partition was investigated. Protein partition coefficient was little influenced by changing PEG molecular mass. Increasing the tie-line length decreased the partition. Increasing the pH also raised the BSA partition coefficient. It is shown that systems formed by PEG and cashew-nut tree gum may be considered as an interesting alternative for use in protein purification.

Performance of a perforated rotating disc contactor in the continuous extraction of a protein using the PEG–cashew-nut tree gum aqueous two-phase system

The characterisation of bovine serum albumin (BSA) mass transfer mechanisms in a perforated rotating disc contactor (PRDC) using an aqueous two-phase system (ATPS) composed of poly(ethylene glycol) (PEG) and a polysaccharide, the cashew-nut tree gum, was described. The PEG-rich phase was used as the dispersed phase and protein transfer took place from the dispersed to the continuous phase. Studies of the effect of dispersed phase velocity, system composition and disc rotation speed on either protein mass transfer coefficients or column hold-up showed that the dispersed phase hold-up and the volumetric mass transfer coefficient increased with increasing the dispersed phase velocity and disc rotation speed.

Partition of proteins in aqueous two-phase systems based on Cashew-nut tree gum and poly(ethylene glycol)

The partitioning of two proteins, bovine serum albumin (BSA) and trypsin was studied in an aqueous poly(ethylene glycol)(PEG)- Cashew-nut tree gum system. The phase diagram was provided for Cashew-nut tree gum and PEG molecular weight of 1500 at two different temperatures. The influence of several parameters including concentrations of polymers, pH, salt addition and temperature on the partitioning of these proteins were investigated.. The results of this research demonstrated the importance of the protein characteristics for partitioning in aqueous biphasic system.

Studies of efficiency in a perforated rotating disc contactor using a polymer-polymer aqueous two-phase systems

The mass transfer process in a perforated rotating disc contactor (PRDC) using a polymer-polymer aqueous two-phase system was investigated. The results show that the efficiency did not show a regular trend with the increase of the dispersed phase velocity and increased with the rotation velocity. The separation efficiency was higher for three rotating discs than for four discs. The increase in tie-line length decreased the efficiency. The separation efficiency reached high values, about 96% under conditions studied in this work.

Physical and rheological characterisation of polyethylene glycol-cashew-nut tree gum aqueous two-phase systems.

The characterisation of the polyethylene glycol-cashew-nut tree gum aqueous two-phase system is described. Factors which affect the phase diagram including polymer molecular mass, pH and temperature were analysed. The physico-chemical properties of the system such as density, viscosity, volume ratio and phase separation times were also described. The characteristics of the system studied indicate it to be very attractive as a separation technique.

Extractive cultivation of xylanase by Penicillium janthinellum in a poly(ethylene glycol)/cashew-nut tree gum aqueous two-phase system.

Cultivation of the fungus Penicillium janthinellum for xylanase production was studied in a poly(ethylene glycol)/cashew‐nut tree gum aqueous two‐phase system, using a two‐level fractional factorial design. The parameters studied were initial pH, cultivation time, type of agro‐industrial residue (oat husk or corn cob), agitation, temperature, and phase‐forming polymers. The xylanase produced during fermentation partitioned into the top phase. The agitation and temperature (negative), cultivation time and initial pH (positive) effects proved statistically significant for xylanase production. The highest percentage yield of the xylanase in the top and its production in the top phase, about 97% and 160.7 U/mL, were obtained in cultures of 120 h, 40 rpm, 25 °C, and pH 5.0.

Social phobia in childhood-onset systemic lupus erythematosus

Anxiety is frequently observed in systemic lupus erythematosus, however the prevalence of phobia has rarely been reported.