The use of peptones as medium additives for the production of a recombinant therapeutic protein in high density perfusion cultures of mammalian cells

Protein hydrolysates as substitutes for serum have been employed by many in cell culture medium formulation, especially with the shift to low protein or protein-free media. More recently, vegetable hydrolysates have also been added as nutritional supplements to fortify the amino acid content in small peptide form for batch and fed-batch fermentations. Several of these new hydrolysates (peptones of soy, rice, wheat gluten etc.) were tested as protein-free medium supplements for the production of a recombinant therapeutic protein. Multiple peptone-supplemented, continuous perfusion bioreactor experiments were conducted, varying dilution rates and basal medium composition over the various runs. Cell specific rates and product quality studies were obtained for the various peptones and compared with peptone-free medium. The potential for peptones to decrease intrinsic and proteolytic degradation of the product was also investigated. It was found that peptones confer a nutritional benefit, especially at low dilution rates, for the recombinant BHK cell line used in this investigation. The specific productivity increased 20-30% compared to the peptone-free controls. However, this benefit was also fully delivered by using fortified medium in place of the peptone-enriched media. Therefore, while peptones may be considered as useful medium additives when development time is limited, their addition may be avoided by systematic medium development if permitted by the time line of the project.