Scale-Up Aspects of PHA Production by Microbial Enrichment Cultures

Polyhydroxyalkanoates (PHAs) are microbial storage polymers accumulated by many different prokaryotes as an intracellular carbon and energy reserve. The polymer properties make PHA interesting as bioplastic. Moreover, the monomers could serve as chiral building blocks or be used as a biofuel.
Currently, PHA is commercially produced using pure cultures and well-defined substrates. To reduce the cost of PHA production and allow broad application, microbial enrichment cultures could be used. This eliminates the need for axenic conditions and allows the use agro-industrial waste streams as substrate, contributing to the development of a circular economy.

The aim of this thesis was to investigate scale-up aspects of the PHA production by microbial enrichment cultures. A translation of the previously developed laboratory process to industrial application raises new questions concerning the impact of (variable) wastewater composition and process design, for example. Chapter 2 and 3, therefore, focus on the fate of different constituents of an acidified waste stream, and the second part (Chapter 4-6) of the thesis focusses on alternative process configurations. Chapter 1 provides a general introduction to the topic and describes the research preceding this thesis. Chapter 7 summarizes and integrates the main findings.