by Stephen F. Gorfien, GIBCO Cell Culture R&D, Invitrogen Corporation William Paul, David Judd, Lia Tescione, and David W. Jayme Cell density, longevity, and expression are the economics of cell cultures in biopharmaceutical production ? and rich growth media are the investment. Glucose and glutamine are primary energy sources for culture growth, but their associated metabolic wastes can actually harm cell cultures. Adapting cell lines to reduced levels of glucose and glutamine, then feeding the culture chemically defined nutrient supplements, increases cell viability, maximizes cell density, and increases product expression.