A biochemically defined culture medium for culturing engineered Chinese hamster ovary (CHO) cell lines, which is essentially free from protein, lipid and carbohydrate isolated from an animal source, having water, an osmolality regulator, a buffer, an energy source, amino acids including L-glutamine, an inorganic or recombinant iron source, and a synthetic or recombinant growth factor, and optionally non-ferrous metal ions vitamins and cofactors. Also cells adapted to grow in such a culture medium.REEXAMINATION RESULTSThe questions raised in reexamination request no. 90/006656, filed Jun. 2, 2003 have been considered and the results thereof are reflected in this reissue patent which constitutes the reexamination certificate required by 35 U.S.C. 307 as provided in 37 CFR 1.570(e), for ex parte reexaminations, or the reexamination certificate required by 35 U.S.C. 316 as provided in 37 CFR 1.997(e) for inter partes reexaminations.