Abstract
Polyhydroxyalkanoates (PHA) are intracellular storage molecules that can be utilized as biodegradable thermoplastic polymers and possess properties similar to common petrochemical plastics (i.e., HDPE). Commercial production currently utilizes pure bacterial cultures grown under macronutrient limitation with a pure feedstock (i.e., glucose and propionic acid), making synthesis of fossil fuel-based plastics more cost-effective. An alternative method, known as aerobic dynamic feeding (ADF), utilizes mixed microbial consortia fed waste organic carbon, which offers the potential to significantly reduce production costs; however, operational parameters must first be established. Research presented herein focused on advancing a three-stage ADF process, which successfully produced PHA-rich biomass on fermented dairy manure, by assessing the effects of sedimentation and solids retention time (SRT) on the consortium enrichment stage. Introduction of sedimentation resulted in lower average maximum intracellular PHA content, 31.7% and 33.6% total solids (w/w), respectively. Increasing enrichment stage SRT increased intracellular PHA and improved operational process control.