title: Production of polyhydroxyalkanoates in open, mixed cultures from a waste sludge stream containing high levels of soluble organics, nitrogen and phosphorus.
abstract: In this study, the production of polyhydroxyalkanoates (PHAs) from waste activated sludge (WAS) was evaluated. PHAs were produced from fermented WAS pretreated via high-pressure thermal hydrolysis, a stream characterised by high levels of nutrients (approximately 3.5 g N L(-1) and 0.5 g P L(-1)) and soluble organics. PHA-storing organisms were successfully enriched at high organic loading rates (6 g COD(sol) L(-1) d(-1)) under aerobic dynamic feeding in sequencing batch reactors at a sludge retention time of 6 d with a short feast length less than 20% of the cycle, and a maximum substrate concentration during feast of 1 g COD(VFA) L(-1). The biomass enrichment, characterised by a decrease in species evenness based on Lorenz curves, provided a biomass that accumulated 25% PHA on a dry-biomass basis with yields on VFA of 0.4 Cmol Cmol(-1) in batch tests. The PHA consisted of ∼70 mol% 3-hydroxybutyrate and ∼30 mol% 3-hydroxyvalerate, and presented high thermal stability (T(d) = 283-287 °C) and a molecular mass ranging from 0.7 to 1.0 × 10(6) g mol(-1). Overall PHA storage was comparable to that achieved with other complex substrates; however, lower PHA storage rates (0.04-0.05 Cmol PHA(-1) Cmol X(-1) h(-1)) and productivities (3-4 Cmol PHA L(-1) h(-1)) were probably associated with a biomass-growth and high-respiration response induced by high levels of non-VFA organics (40-50% of COD(sol) in feed) and nutrients. PHA production is feasible from pretreated WAS, but the enrichment and accumulation process require further optimisation. A milder WAS pretreatment yielding lower levels of non-VFA organics and readily available nutrients may be more amenable for improved performance.
authors.affiliation: AnoxKaldnes AB, Klosterängsvägen 11A, 226 47 Lund, Sweden. fernando.morgan@anoxkaldnes.com
authors.forename: Fernando
authors.initials: F
authors.lastname: Morgan-Sagastume
authors.forename: Anton
authors.initials: A
authors.lastname: Karlsson
authors.forename: Peter
authors.initials: P
authors.lastname: Johansson
authors.forename: Steven
authors.initials: S
authors.lastname: Pratt
authors.forename: Nico
authors.initials: N
authors.lastname: Boon
authors.forename: Paul
authors.initials: P
authors.lastname: Lant
authors.forename: Alan
authors.initials: A
authors.lastname: Werker
mesh_terms: D001419:Bacteria / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology; D058645:Denaturing Gradient Gel Electrophoresis; D005232:Fatty Acids, Volatile / Q000032:analysis; D005285:Fermentation; D009584:Nitrogen / Q000032:analysis*; D009930:Organic Chemicals / Q000032:analysis*; D010100:Oxygen / Q000032:analysis; D010758:Phosphorus / Q000032:analysis*; D054813:Polyhydroxyalkanoates / Q000096:biosynthesis*; D016133:Polymerase Chain Reaction; D012722:Sewage / Q000382:microbiology*; D012995:Solubility; D014865:Waste Disposal, Fluid
chemical_list: D005232:Fatty Acids, Volatile; D009930:Organic Chemicals; D054813:Polyhydroxyalkanoates; D012722:Sewage; D010758:Phosphorus; D009584:Nitrogen; D010100:Oxygen