The effects of culture temperature and pH on cell growth and recombinant human bone morphogenetic protein-4 (rhBMP-4) production were investigated to maximize rhBMP-4 production from Chinese hamster ovary cells. Cells were cultivated in a bioreactor at different culture pH levels (6.7, 6.9, 7.2, and 7.5) and temperatures (37 degrees C and 33 degrees C). The highest rhBMP-4 concentration (4.6 +/- 0.5 mu g/mL) was obtained at pH 7.2 and 37 degrees C. Regardless of culture temperature and pH, significant rhBMP-4 degradation via increased proteolytic activity was observed in the decline growth phase. Protease inhibitors such as EDTA and leupeptin were toxic and thus did not enhance rhBMP-4 production. High viability was achieved in repeated batch cultures with frequent medium exchanges. These cultures showed enhanced rhBMP-4 productivity, demonstrating the potential of repeated batch cultures as a means for improved rhBMP-4 production. (C) 2016 Elsevier Ltd. All rights reserved.