Monitoring of Polyhydroxyalkanoate (PHA) Production during High-Cell-Density Plant Oil Cultivations Using Photon Density Wave Spectroscopy.

Polyhydroxyalkanoates (PHAs) are biodegradable plastic-like materials with versatile properties. Plant oils are excellent carbon sources for a cost-effective PHA production, due to their high carbon content, large availability, and comparatively low prices. Additionally, efficient process development and control is required for competitive PHA production, which can be facilitated by or monitoring devices. To this end, we have evaluated photon density wave (PDW) spectroscopy as a new process analytical technology for () H16 plant oil cultivations producing polyhydroxybutyrate (PHB) as an intracellular polymer. PDW spectroscopy was used for recording of the reduced scattering coefficient ' and the absorption coefficient at 638 nm. A correlation of ' with the cell dry weight (CDW) and with the residual cell dry weight (RCDW) was observed during growth, PHB accumulation, and PHB degradation phases in batch and pulse feed cultivations. The correlation was used to predict CDW, RCDW, and PHB formation in a high-cell-density fed-batch cultivation with a productivity of 1.65 g·L·h and a final biomass of 106 g·L containing 73 wt% PHB. The new method applied in this study allows monitoring of CDW, RCDW, and PHA formation.