Regulation of Glucose Metabolism – A Perspective From Cell Bioprocessing

Improvements in protein production in mammalian cells from targeted metabolic engineering

Bioprocess optimization has yielded powerful clones for biotherapeutic production. However, new genomic technologies allow more targeted approaches to cell line development. Here we review efforts to enhance protein production in mammalian cells through metabolic engineering. Most efforts aimed to reduce toxic byproducts accumulation to enhance protein productivity. However, recent work highlights the possibility of regulating other desirable traits (e.g., apoptosis and glycosylation) by targeting central metabolism since these processes are interconnected. Therefore, as we further detail the pathways underlying cell growth and protein production and deploy diverse algorithms for their analysis, opportunities will arise to move beyond simple cell line designs and facilitate cell engineering strategies with complex combinations of genes that together underlie a phenotype of interest.

Aerobic expression of Vitreoscilla hemoglobin improves the growth performance of CHO-K1 cells

Inefficient carbon metabolism is a relevant issue during the culture of mammalian cells for the production of biopharmaceuticals. Therefore, cell engineering strategies to improve the metabolic and growth performance of cell lines are needed. The expression of Vitreoscilla stercoraria hemoglobin (VHb) has been shown to significantly reduce overflow metabolism and improve the aerobic growth of bacteria. However, the effects of VHb on mammalian cells have been rarely studied. Here, the impact of VHb on growth and lactate accumulation during CHO-K1 cell culture was investigated. For this purpose, CHO-K1 cells were transfected with plasmids carrying the vgb or gfp gene to express VHb or green fluorescence protein (GFP), respectively. VHb expression increased the specific growth rate and biomass yields on glucose and glutamine by 60 %, and reduced the amount of lactate produced per cell by 40 %, compared to the GFP-expression controls. Immunofluorescence microscopy showed that VHb is distributed in the cytoplasm and organelles, which support the hypothesis that VHb could serve as an oxygen carrier, enhancing aerobic respiration. These results are useful for the development of better producing cell lines for industrial applications.