Fractionation and purification of the phycobiliproteins from Spirulina platensis.

C-Phycocyanin and allophycocyanin of Spirulina platensis are fractionated and purified using a non-chromatographic method namely, aqueous two phase extraction for the first time. Optimized process parameters of aqueous two phase extraction (PEG 4000/potassium phosphate of tie line length 18.64% with a phase volume ratio 1.45) resulted in pure C-phycocyanin and allophycocyanin with a purity of 3.23 and 0.74, respectively, in a single extraction. Multiple extractions (two) improved the purity of C-phycocyanin from 3.23 to 4.02. Integration of aqueous two phase extraction with membrane process not only facilitated the separation of phase forming components from the products and also increased the purity of allophycocyanin from 0.74 to 1.5.

Method to obtain C-phycocyanin of high purity.

A new approach is made for the purification of C-phycocyanin (C-PC), which is simple and more efficient than existing methods. The proposed method involves two steps: aqueous two phase extraction and ion-exchange chromatography. Crude extract of C-phycocyanin, of purity 1.18, obtained from Spirulina platensis is subjected to aqueous two phase extraction. C-phycocyanin obtained from this process showed a purity of 5.22, which is higher than the reported value till date. In order to explore the possibility of further purification, C-phycocyanin is subjected to ion-exchange chromatography and found that the purity increased from 5.22 to 6.69. The fluorescence, intactness of structure and purity of C-phycocyanin are confirmed using spectrofluorometry, circular dichroism spectra and sodium dodecyl sulfate-polyacrylamide gel, respectively.

Drop formation in aqueous two-phase systems.

Extraction using aqueous two-phase systems (ATPSs) is a versatile technique for the downstream processing of various proteins/enzymes. The study of drop formation deals with the fundamental understanding of the behavior of liquid drops under the influence of various external body as well as surface forces. These studies provide a basis for designing of the extractions in column contactors in which liquid drops play a major role. Most of the drop formation studies reported so far is restricted to aqueous-organic systems. ATPSs, differ from aqueous-organic systems in their physical properties. In view of this, an attempt was made to develop a model for drop formation in ATPSs adopting the information available on aqueous-organic systems. In order to validate the model, experiments were performed by using polyethylene glycol (PEG)/salt systems of different phase compositions at various flow rates. At low flow rates the single stage model and at high flow rates the two stage model are able to predict the drop volume during its formation from tip of capillary. The experimental results were found to agree reasonably well with those predicted by the model.