Production of recombinant proteins using Chinese hamster ovary (CHO) cells is the most successful platform for large-scale production in the biopharmaceutical industry worldwide (Walsh, 2014). This has been mainly achieved by establishment of high producer cell lines and process optimization approaches such as optimization of cell culture media. The best performing and stable producer cell lines would never achieve titers in the g/L range, if they were cultivated in poor media which do not satisfy the cells nutritional needs. Further, all process steps of recombinant protein production, from cell line development to the final product, have to be considered as a whole, since each step may have detrimental effects on protein yield and product quality. Nonetheless, the choice of a properly defined and balanced cultivation medium is one of the most critical steps with respect to therapeutic protein products. In this project an in-house developed chemically defined cell culture medium formulation (MV3-2) was benchmarked against a commercially available formulation in order to identify critical aspects for further optimization of the current formulations (basal medium + feed media). Moreover, various types of media supplements were evaluated towards their potential to improve general process performance and to boost product titers. The results show that the performance of the basal medium could be improved by 70 % in regard of product titers. However, the in-house developed feeding medium still has some room for improvement, since product titers and general culture performance were lower compared to a commercial feeding medium. Supplementation with media additives (D(+)-trehalose, D(+)-mannose, taurine, glutathione, lipids, valproic acid and glycerol) showed quite promising results for some additives, concerning increased product titers and applicability.