TFTAK supported Metrosert in building a stronger foundation for bioprocess scale-up

In a recent project, TFTAK supported AS Metrosert in advancing their standard procedures for both intracellular and extracellular protein production.

The project work focused on finding ways to support faster startup when new process equipment is added or new processes introduced, and to create a clear framework for troubleshooting. We worked with two model processes at two different scales: 1 L scale and 70 L scale to establish and optimize baseline and to evaluate scale-up effects such as oxygen transfer, feed rate and downstream processing.

Learnings from this scale-up work directly support the next step at Metrosert's soon-to-open pilot facility, where the same processes can be run at up to 5,000 L scale.

How did we do that?

For the intracellular model process, we used E. coli producing RFP and developed a fed-batch workflow with a glucose-mineral medium. We defined medium composition based on a target biomass level of 50 gdw/L and verified experimentally that N and P were not limiting. The tests showed that post-induction growth time had a clear effect on final protein concentration - slower feed and longer cultivation after induction gave a better result. When transferring to 70 L, we confirmed fully aerobic conditions by showing that formate, acetate and residual glucose remained below the analytical detection threshold.

For the extracellular model process, we worked with K. phaffii strains producing ice-binding protein. We compared 2 strains, assessed expression by SDS-PAGE and Bradford assay, and measured functional activity through ice recrystallisation inhibition. The more active strain was taken from 1 L forward to 70 L, where we tested process adjustments such as ~1.3 bar overpressure and ethanol-glucose co-feeding to manage oxygen demand. We also described downstream steps including plate centrifugation, microfiltration and ultrafiltration for a ~14 kDa protein.

Key outcomes

From these model processes, we derived a set of scalable standard procedures that enable more precise description of production steps, facilitate root-cause analysis when process behavior changes, and support robust pilot-scale transfer and operations. For us, the project added practical experience in scale-up, analytical process support and bioprocess documentation.

We wish Metrosert continued success as it moves towards the top tier of the bioeconomy.