Optimized biosynthesis of polyhydroxybutyrate using a continuous process

In the ModiBioPol research project, a new process for the continuous biosynthesis of the biopolymer polyhydroxybutyrate (PHB) was developed. The aim was to minimize process variability so that key material properties such as molecular weight and mechanical stability can be specifically adjusted. In addition, environmentally friendly methods for polymer purification were tested in order to replace chlorinated solvents.

PHB belongs to the group of bio-based and biodegradable thermoplastics, whose importance is growing due to the focus on sustainable materials. However, industrial production is complex, especially the extraction of the polymer from the fermentation broth. As part of ModiBioPol, the SKZ Plastics Center in Würzburg and Prof. Stute’s research group at Nuremberg Institute of Technology are working together on more efficient production processes.

Until now, PHB has been produced using the discontinuous fed-batch process. The challenge was to convert this process into a continuous system while ensuring a uniform chain length of the polymer. To this end, an optimized fermentation process was developed that allows the polymer structure to be influenced in a targeted manner by controlling the residence time and synthesis parameters. At the same time, new extraction methods were researched in order to increase the thermal and chemical stability of the polymers.

“We are very satisfied with the results of ModiBiopol. We have succeeded in enabling the continuous biosynthesis of PHB for more than 1,000 hours. At the same time, we are also so satisfied with the technical/economic and ecological findings that we are aiming for follow-up projects in the near future,” explains Dr. Oliver Tröppner, Group Leader Materials Development at SKZ.

A key success factor was the optimization of downstream processing, which enabled more efficient polymer processing. As a member of the Zuse Association, the SKZ supports SMEs in particular with its research in order to make innovative processes usable for industrial applications.