Methods for removal of microcystins and isolation of phycocoyanin from cyanobacteria
This disclosure relates to methods of removing contaminating microcystins toxins from preparations of blue-green algae. It also relates to methods of purifying phycocyanin from blue-green algae extracts.
1. A method of isolating phycocyanin from blue-green algae comprising:
suspending dried, fresh or frozen blue-green algae in a medium consisting of water to produce a cell suspension;
disrupting the integrity of the blue-green algae cells in the medium, thereby releasing cytoplasmic contents into the medium, to produce a disrupted cell suspension; separating solid and a first soluble phases of the disrupted cell suspension;
contacting the first soluble phase of the disrupted cell suspension with a non-ionic polyaromatic macroreticular adsorbent resin having a surface area of 450 to 900 meters (m) 2 /gram(g);
collecting a second soluble phase from the resin to produce a phycocyanin extract comprising less than 5 parts per billion (ppb) microcystins; and optionally dehydrating the phycocyanin extract.
2. The method of claim 1 , further comprising contacting the phycocyanin extract with a bed of silica gel; collecting a third soluble phase phycocyanin from the silica gel; and optionally dehydrating the third soluble phase phycocyanin.
3. The method of claim 2 , further comprising contacting the third soluble phase phycocyanin with a bed of aluminum oxide; collecting a fourth soluble phase phycocyanin from the aluminum oxide; and optionally dehydrating the fourth soluble phase phycocyanin.
4. The method of claim 3 , further comprising contacting the fourth soluble phase phycocyanin with a bed of activated charcoal; collecting a fifth soluble phase phycocyanin; and optionally dehydrating the fifth soluble phase phycocyanin.
5. The method of claim 1 , wherein the resin is packed into a column and wherein contacting the first soluble phase of the disrupted cell suspension comprises passing the first soluble phase of the disrupted cell suspension through the column.
6. The method of claim 5 , wherein the column has an adsorption capacity of 1-10 bed volumes.
7. The method of claim 1 , wherein disrupting the integrity of the blue-green algae cells comprises homogenizing, sonicating or freezing and thawing the cells.
8. The method of claim 1 , wherein separating solid and first soluble phases of the disrupted cell suspension comprises filtering or centrifuging the disrupted cell suspension and collecting the first soluble phase.
9. The method of claim 1 , wherein the blue-green algae is Aphanizomenon flos aquae or a species of Spirulina.
10. The method of claim 1 , wherein said resin comprises a pore volume of 0.6 to 1.8 milliliters per gram.
11. The method of claim 1 , wherein said second soluble phycocyanin extract contains less than 1 part per billion (ppb) microcystins.
12. The method of claim 1 , wherein the water is deionized water.