Method for removing impurities from biopolymer material
The present invention relates to a method for removing impurities from biopolymer material, e.g. polysaccharides, polypeptides or polynucleotides. More particularly, the present invention provides a method of reducing lipopolysaccharide levels in a lipopolysaccharide containing biopolymer material, comprising the successive steps of: a) providing an aqueous solution containing 0.05-50 wt. % of dissolved lipopolysaccharide-containing biopolymer material; 0.001-10 wt.% of a surfactant; 0.05-15 wt. % of solid adsorbent; and at least 50 wt. % of water; b) allowing the adsorbent to adsorb lipopolysaccharides; c) separating the solid adsorbent containing adsorbed lipopolysaccharides from the remaining aqueous solution; and d) recovering the biopolymer material containing a reduced level of lipopolysaccharide from the separated aqueous solution.
1. A method of reducing lipopolysaccharide levels in a lipopolysaccharide containing alginate, said method comprising:
(a) providing an aqueous solution containing 0.05-50 wt. % of dissolved lipopolysaccharide-containing alginate; 0.001-10 wt. % of a surfactant; 0.05-15 wt. % of solid adsorbent; and at least 50 wt. % of water;
(b) allowing the solid adsorbent to adsorb lipopolysaccharides;
(c) separating the solid adsorbent containing adsorbed lipopolysaccharides from the remaining aqueous solution by means of centrifugation, sedimentation or filtration; and
(d) recovering the alginate containing a reduced level of lipopolysaccharide from the separated aqueous solution.
2. The method according to claim 1 , in which the separating is by means of centrifugation, sedimentation, filtration, or a combination thereof.
3. The method according to claim 1 , wherein the surfactant is a micelle-forming surfactant in a concentration exceeding the critical micelle concentration.
4. The method according to claim 3 , wherein the micelle-forming surfactant has a density in excess of 1.03 g/ml at the cloud point temperature.
5. The method according to claim 3 , wherein prior to (c), said aqueous solution is caused to phase separate into an aqueous phase and a surfactant phase.
6. The method according to claim 3 , wherein the micelle-forming surfactant is an alkylphenol ethoxylate represented by the formula C x H 2x+1 —C 6 H 4 —O—(C 2 H 4 O) n H, wherein:
x is within the range of 4-12; and
n is within the range of 4-12.
7. The method according to claim 1 , wherein the separated aqueous phase has a viscosity of at least 100 cSt at 20° C.
8. The method according to claim 1 , wherein the solid adsorbent is selected from the group consisting of activated carbon, clays and combinations thereof.
9. The method according to claim 8 , wherein the solid adsorbent comprises activated carbon.
10. The method according to claim 8 , wherein the solid adsorbent comprises an adsorbent clay.
11. The method according to claim 5 , wherein the phase separation is induced by increasing temperature, adding salt, changing pH and/or osmotic stress.
12. The method according to claim 1 , wherein the alginate is sodium alginate.
13. The method according to claim 1 , wherein the recovering (d) comprises precipitating the alginate by adding at least 10% by weight of water of an organic solvent that is miscible with water.