The new era of metabolic study is enabling a molecular rationalisation of cellular processes that support high production and quality of recombinant protein in bioprocessing. The completeness of, and confidence in, our understanding of culture metabolism has permitted the development of metabolic models for recombinant cell lines that will facilitate enhancement of bioprocess performance. For Chinese Hamster ovary (CHO) cell lines, key indicators of metabolic events linked to productivity have become clear in the past 2-3 years. In particular, the balance between glycolysis and the citric acid cycle appears as a determinant/indicator of both growth and productivity. The profiles observed offer potential to direct CHO cell function during culture through medium design and/or cell engineering. © 2014 Elsevier Ltd.