An in 2016 published DECHEMA guideline concerning process engineering characterization and a new Escherichia coli model process were utilized for the qualification of two geometrically similar stirred stainless steel bioreactors (30 L and 100 L working volume). The achieved results demonstrate that performing an additional biological model process is a valuable complement to the process engineering characterization. Optical densities of 27 (100 L) and 39 (30 L) were reached in the batch cultivation process.

During the last decades single‐use bioreactors have become widely accepted in the biopharmaceutical industry. Single‐use technologies bring many advantages over conventional solutions, such as a reduced investment and operational cost as well as an optimized time‐to‐market. So far, this type of bioreactor is mainly used for cell culture applications. Results for microbial fermentations are rarely found, commonly due to limited oxygen transfer rates. The aim of this study was to establish a high cell density fermentation process for a recombinant Escherichia coli considering a rocking motion type and an adapted stirred 50‐L single‐use bioreactor. By using the design space approach an OTRmax/OURmax model was established. The feeding strategies were optimized and verified based on a model for both single‐use systems to achieve high cell densities. In both single‐use bioreactors a recombinant protein was successfully expressed.

: Microbial fermentations are of major importance in the field of biotechnology. The range of applications is rather extensive, for example, the production of vaccines, recombinant proteins, and plasmids. During the past decades single-use bioreactors have become widely accepted in the biopharmaceutical industry. This acceptance is due to the several advantages these bioreactors offer, such as reduced operational and investment costs. Although this technology is attractive for microbial applications, its usage is rarely found. The main limitations are a relatively low oxygen transfer rate and cooling capacity. The aim of this study was to examine a stirred single-use bioreactor for its microbial suitability. Therefore, the important process engineering parameters volumetric mass transfer coefficient (k L a), mixing time, and the heat transfer coefficient were determined. Based on the k L a characteristics a mathematical model was established that was used with the other process engineering parameters to create a control space. For a further verification of the control space for microbial suitability, Escherichia coli and Pichia pastoris high cell density fermentations were carried out. The achieved cell density for the E. coli fermentation was OD600 = 175 (DCW = 60.8 g/L). For the P. pastoris cultivation a wet cell weight of 381 g/L was reached. The achieved cell densities were comparable to fermentations in stainless steel bioreactors. Furthermore, the expression of recombinant proteins with titers up to 9 g/L was guaranteed.