Patent ID: 7547529

Claim:
A method for producing a polypeptide comprising a serine residue comprising: (i) culturing, in a medium, transformed host cells that produce a recombinant atrial natriuretic peptide comprising a serine residue and a byproduct polypeptide comprising an O-acetylserine residue in place of a serine residue in the atrial natriuretic peptide; (ii) adding at least 3 g/L methionine and at least one of at least 3 g/L histidine or at least 3 g/L glycine to the medium; and (iii) reducing the formation of said byproduct polypeptide, wherein the formation of said byproduct polypeptide is reduced in an amount greater than or equal to 50% as compared to a control medium with no methionine, histidine, or glycine added.