Abstract
Polyhydroxyalkanoates (PHAs) are biodegradable, biologically produced plastics with the potential to replace conventional, fossil fuel derived plastics. PHAs can be synthesized from otherwise undesired organic-rich waste streams, yielding a valuable commodity while achieving greater sustainability. To be economically successful, however, the PHA production process must be optimized and have design guidelines established. In this work, using fermented dairy manure as a model substrate, a 12-month evaluation assessed the long-term enrichment of a mixed microbial consortia dominant in PHA producers. Process control challenges led to mixed results, but a maximum intracellular PHA content of 64.7% (total solids) or 74.8% (volatile solids) was obtained. In addition, PHA production employing continuous substrate addition mode as opposed to traditional fed-batch improved operations and process control. Intracellular PHA content was strongly correlated with PHA yield on substrate, a previously overlooked metric, forging a clearer path to process optimization and full scale design.