Variation in recombinant protein expression levels among clones of lepidopteran cell populations

The effect of oscillating dissolved oxygen concentrations on the metabolism of a Spodoptera frugiperda IPLB-Sf21-AE clonal isolate

The effect of oscillating dissolved oxygen (DO) concentration on the metabolism of a clonal isolate of the Spodoptera frugiperda IPLB-Sf21-AE insect cell line was investigated. Specifically, the effect on cell growth, re- combinant protein synthesis, glucose and glutamine consumption, and lactate accumulation was determined. Prior to conducting the oscillating DO experiments, it was found that the DO concentration could be reduced to 15% air saturation without adversely affecting the growth rate. Under these conditions, glucose and glutamine became depleted as the maximum cell density was reached. The introduction of DO oscillations, that is, cycles consisting of 30 min at 15% DO followed by 30 min of anoxia, significantly altered cell metabolism, including inhibition of cell growth and recombinant protein synthesis. The effect of DO oscillations on glucose consumption was dependent on the experimental conditions. Glucose exhaustion occurred when the DO oscillations contained either an "apparent" anoxia period (nitrogen sparging discontinued upon reaching 0% DO) without pH control or a "true" anoxia period (nitrogen sparging continued throughout anoxia period) with pH control. Glucose consumption was significantly decreased, however, when the cells were exposed to a "true" anoxia period without pH control, that is, low pH inhibited glucose utilization. Glutamine uptake was not significantly affected by DO oscillations. Lactate only accumulated in the oscillating DO runs, a finding consistent with previous results demonstrating that significant lactate accumulation only occurs under DO-limited conditions. (c) 1995 John Wiley & Sons, Inc.