Methods and processes for improved recombinant protein production are provided. The methods are useful for production of growth factors, particularly those of the TGF-&bgr； superfamily, including bone morphogenetic proteins (BMPs), such as BMP-2. Suitable host cells are cultured in media where iron is present at a concentration of at least 2.25 &mu；M and if pyridoxal is present, it makes up less than 55% of the molar concentration of vitamin B6 in the media.
