Rapid Recovery of Mixed Culture Polyhydroxyalkanoate Production System from Extracellular Polymeric Substances Bulking Using Azithromycin

Abstract

The long-term stable operation of the mixed culture polyhydroxyalkanoate(PHA)enrichment stage is the guarantee for the continuous synthesis of PHA, however extracellular polymeric substances (EPS) sludge bulking occurred from time to time may cause the operation fail. In order to solve this problem, as a quencher of signal molecules and antibiotic, azithromycin (AZM) was used in the two reactors with different modes to recover the sedimentation capacity of the sludge. The results showed that AZM addition resulted in the reduction of polysaccharide /protein (PS/PN) ratio in EPS and significant improvement of the sedimentation capacity of the sludge. Quorum quenching of AZM or aiiA gene maintains the sedimentation ability of the sludge. By adding AZM, the growth of Thauera and Flavobacterium , which caused sludge bulking, was inhibited. Paracoccus , a strong PHA producer, has been enriched to ensure that the maximum PHA synthesis of the system was not affected.

Keywords: extracellular polymeric substances (EPS), bulking, polyhydroxyalkanoate, azithromycin, Quorum sensing