The removal of endotoxins from protein solutions using column packings with aminated poly (γ-methyl L-glutamate) spheres

Summary

A method is described for the selective removal of endotoxins from various protein solutions using columns packed with aminated poly (γ-methyl L-glutamate) (PMLG-NH₂) spheres. The PMLG-NH₂ adsorbents showed a high adsorbing activity for endotoxins which had an ionic strength of μ=0.05–1.0 and pH 5.0–9.0. The endotoxin-adsorbing capacity per millitre of the wet adsorbent increased from 0.40 to 1.35 mg (E. coli O111: B4 LPS) at μ=0.2 and pH 7.0 while the aminogroup content of the adsorbent increased from 0.8 to 3.5 meq g⁻¹. The PMLG-NH₂-3.5 has an amino-group content of 3.5 meq g⁻¹. This column packing selectively adsorbed endotoxins, without loss of the protein, from a γ-globulin or cytochromec solution which contained endotoxins at μ=0.05 and pH 7.0. On the other hand, when bovine serum albumin (BSA) was present in solution with endotoxins, both the endotoxins and the BSA were adsorbed by the column. The BSA-adsorbing activity increased with increasing amino-group content of the adsorbent. However, this undesirable adsorption was suppressed with increasing ionic strength of the buffer. As a result, when the packing which had an amino-group content of 1.5 meg g⁻¹ was used in conditions of μ=0.2 and pH 7.0, the endotoxins were removed from a BSA-containing solution without affecting the recovery of the BSA.