Utilizing the tubular bioreactor for continuous recovery of secreted fusion protein from recombinant Escherichia coli

In order to improve the cultivation properties of a traditional continuous stirred tank reactor (CSTR), we introduced a circulation unit made of four inorganic membranes in stainless steel tubes in parallel configuration, the so-called Tubular Bioreactor (TBR). Furthermore, the TBR outlet tube, which has a restriction nozzle at the end, was installed on top of the fermentor vessel, thereby creating a strong jet flow into the reactor and thus improving the mixing and the oxygen transfer rate. The k _La could be increased by approximately 50%. This setup was used for cultivations of recombinant Escherichia coli in a minimal medium and high cell density. More than 50 g dry cell mass/dm³ was obtained. Simultaneously, we have produced an elongated form of human insulin-like growth factor II, which was a secreted fusion protein utilizing the E. coli secretion system based on staphylococcus protein A. The product could be recovered continuously through the TBR-membrane.