Impact of Famine Length on the Structure and Performance of a PHA-Accumulating Community Under Uncoupled Feeding

Polyhydroxyalkanoates (PHAs) is a group of polymers that have emerged as potential alternatives to conventional plastic to their biodegradable nature and versatile composition in various sectors. PHAs are synthesized naturally by diverse microorganisms and act as energy and carbon reserves. Current industrial PHA production relies on specific bacterial strains, necessitating high purity substrates and sterile environments, leading to high production costs. To enhance economic viability, several strategies are being explored, including using mixed microbial communities (MMCs). The widely accepted Aerobic Dynamic Feeding (ADF) method involves ecological selection by shifting between excess (feast) and limited (famine) external substrates. To improve productivity, a novel approach, uncoupled feeding, was introduced within the traditional feast and famine regime. This study highlights the influence of nutrient limitations and famine duration on PHA accumulation and microbial community evolution using activated sludge from a tannery wastewater treatment plant (WWTP) as inoculum. Results indicated slightly better PHA accumulation under nitrogen limitation in terms of both productivity and PHA/VSS ratio, but phosphorus limitation with a longer famine phase showed improved performance in PHA/VSS percentage. Microbial dynamics revealed consistent changes in dominant PHA-accumulating genera under different nutrient limitations but not at different famine durations.