A new method for the direct isolation of glycine from protein hydrolysates

Abstract

Glycine is precipitated directly with copper picrate. After removal of humin and SO4= with Ca(OH)2 and Ba(OH)2 successively and excess Ca with oxalate, solid copper picrate is added (20% in excess of double the amount calculated to combine with glycine present for 1 picrate:2 of amino acid) and warmed. On cooling, the glycine-copper picrate crystallizes out. After washing and recrystallizing, the complex is hydrolyzed with 10% (v/v) H2SO4 on a steam bath for 1 hour. Picric acid is removed with hot benzene and Cu2+ with H2S. After removing H2SO4 with Ba(OH)2, and concentration, glycine was precipitated with ethanol. The complex could be obtained in neutral, basic and anhydrous forms. The procedure leaves an hydrolysate still suitable for the isolation of other amino acids.