Method for removing endotoxin from proteins
Disclosed is a method for removing endotoxin from proteins. Also disclosed are products made by using the method. The method may be used, for example, to produce endotoxin-free lactoferrin. Bovine milk-derived lactoferrin may be produced in commercial quantities by the method, and endotoxin-free bovine lactoferrin may be used for a variety of therapeutic uses, including improving wound healing.
1. A product comprising an endotoxin-free protein made by removing bound endotoxin from an endotoxin-binding protein by a method comprising the steps of
(a) binding the endotoxin-binding protein to a cation exchange resin;
(b) eluting the bound endotoxin from the endotoxin-binding protein using a low ionic strength solution in the absence of added surfactant; and
(c) eluting the endotoxin-binding protein from the cation exchange resin with a high ionic strength solution;
wherein the endotoxin-binding protein is a lactoferrin, lactoferricin, or lactoperoxidase and the endotoxin-free protein comprises less than about 20 endotoxin units per milligram of protein.
2. The product of claim 1 wherein the endotoxin-binding protein is lactoferrin.
3. The product of claim 1 wherein the low ionic strength solution of step (b) is a 0.01 to 0.5 molar salt solution.
4. The product of claim 1 wherein the low ionic strength solution of step (b) is a 0.25 to 0.35 molar salt solution.
5. The product of claim 1 wherein the high ionic strength solution is an 80-100 mS/cm salt solution.