Process conditions affect properties and outcomes of polyhydroxyalkanoate accumulation in municipal activated sludge

The developments of mixed culture polyhydroxyalkanoate production has been directed to maximize the biomass
PHA content with limited attention to polymer quality. Direct comparison of PHA accumulation literature is
challenging, and even regularly contradicting in reported results, due to underlying differences that are not well
expressed. A study was undertaken to systematically compare the commonly reported process conditions for PHA
accumulation by full-scale municipal activated sludge. A biomass acclimation step combined with a pulse-wise
feeding strategy resulted in maximum average PHA contents and product yields. pH control and active nitrification
did not result in observable effects on the PHA productivity. Under these conditions a high molecular
weight polymer (1536 ± 221 kDa) can be produced. Polymer extraction recoveries were influenced by the PHA
molecular weight. A standard protocol for an activated sludge PHA accumulation test including downstream
processing and standardized extraction has been developed and is available as supplementary material.