Influence of scale-up on the quality of recombinant human growth hormone

The aerobic fed-batch production of recombinant human growth hormone (rhGH) by Escherichia coli was studied. The goal was to determine the production and protein degradation pattern of this product during fed-batch cultivatio n and to what extent scale differences depend on the presence of a fed-batc h glucose feed zone. Results of laboratory bench-scale, scale-down (SDR), a nd industrial pilot-scale (3-m(3)) reactor production were compared. In add ition to the parameters of product yield and quality, also cell yield, resp iration, overflow, mixed acid fermentation, glucose concentration, and cell lysis were studied and compared. The results show that oxygen limitation f ollowing glucose overflow was the critical parameter and not the glucose ov erflow itself. This was verified by the pattern of byproduct formation wher e formate was the dominating factor and not acetic acid. A correlation betw een the accumulation of formate, the degree of heterogeneity, and cell lysi s was also visualized when recombinant protein was expressed. The productio n pattern could be mimicked in the SDR reactor for all parameters, except f or product quantity and quality, where 30% fewer rhGH-degraded forms were p resent and where about 80% higher total yield was achieved, resulting in 10 % greater accumulation of properly formed rhGH monomer. (C) 2000 John Wiley & Sons, Inc.