Bioprocess parameters of cell growth and human μ opioid receptor expression in recombinant Drosophila S2 cell cultures in a bioreactor

Abstract

The paper describes a recombinant Schneider 2 (rS2) cell culture and protein expression in a bioreactor. S2 cells were transfected with a plasmid containing a fusion protein (human μ opioid receptor, hMOR, and green fluorescent protein, EGFP) under the control of inducible metallothionein promoter. A bioprocess in a bioreactor with 5% dissolved oxygen, 27°C and 120 rpm enabled the cell culture to attain 5.3×10⁷ viable cells/mL at 96 h. The induction decreased the cell multiplication (2.5×10⁷ viable cells/mL at 72 h). Glutamine and glucose and low levels of lactate were consumed. A fast recombinant protein synthesis took place and, at 6 h of induction, 2×10⁴ receptors/cell could be detected by a functional binding assay. Fluorescence measurements showed a progressive increase of recombinant protein expression with a maximal value of 1.26×10⁵ fluo counts/s at 24 h of induction. The data shown in this paper indicate a practical and scaleable cell culture bioprocess procedure for the preparation of recombinant proteins expressed in S2 cells.