No abstract

This study investigated the influence of enrichment temperature on the accumulation ability of polyhydroxybutyrate (PHB) and the composition of PHB-accumulating microorganisms (PHBAMOs) in mixed microbial cultures obtained from activated sludge. PHBAMOs were enriched using the feast-famine method in sequencing batch reactors that were fed with acetate as the sole external carbon source and controlled at 20℃ or 28℃. Batch PHB accumulation experiments under nitrogen-and phosphorus-deficient conditions revealed that the maximum content and yield of PHB in the two enrichment cultures were twice as high as the seed sludge. The results indicated that the PHB accumulation ability of the sludge can be greatly enhanced by enrichment using the feast-famine method, irrespective of temperature. Through clone library analysis targeting the phaC genes, PHBAMOs belonging to Rhodocyclales, specifically Thauera, were found to be notably increased after enrichment, although Burkholderiales were dominant in the seed sludge. The increase of PHBAMOs belonging to Rhodocyclales was greater in the enrichment culture obtained at 20℃, which had a slightly stronger PHB accumulation ability, as compared with that at 28℃. These results suggest that Rhodocyclales may be the key members enhancing PHB accumulation abilities of the enrichment cultures.