title: Enrichment of a mixed microbial culture for polyhydroxyalkanoates production: Effect of pH and N and P concentrations.
abstract: Polyhydroxyalkanoates (PHA) are biopolymers that can be an alternative against conventional plastics. The study reported herein evaluated the enrichment of a mixed microbial culture (MMC) operated under feast/famine regime and different pHs in a sequencing batch reactor (SBR) using acetate as sole carbon source to produce polyhydroxyalkanoates (PHAs). The enrichment step was evaluated at controlled pH of 7.5 and also without pH control (averaged value of 9.0). The acetate uptake rate (-qS) of both enrichments at the end of the experimental period exhibited similar behaviour being about 0.18CmolAcCmolX-1h-1and 0.19CmolAcCmolX-1h-1for SBR-A and SBR-B, respectively. However, the PHA-storing capacity of the biomass enriched without pH control was better, exhibiting a maximum PHA content of 36% (gPHAg-1VSS) with a PHA production rate (qPHA) of 0.16CmolPHACmolX-1h-1. Batch experiments were performed to evaluate PHA-storing capacity of the enriched culture at different pHs and nutrients concentrations. In the pH experiments (without nutrient limitation), it was found that in the absence of controlled pH, the enriched biomass exhibited a PHA content of 44% gPHAg-1VSS with -qSand PHA to substrate yield (YPHA/Ac) of 0.57CmolAcCmolX-1h-1and 0.33CmolPHACmolAc-1, respectively. Regarding the experiments at variable nutrients concentration (pH ranging 8.8 to 9.2), the results indicate that the PHA content in the enriched biomass is significantly higher being around 51% gPHAg-1VSS under nitrogen limitation. This work demonstrated the feasibility of the enrichment of a MMC with PHA storage ability without pH control. Results also suggest that better PHAs contents and substrate uptake rates are obtained without controlling the pH in the accumulation step. Finally, this work also highlights the importance of understanding the role of nutrients concentration during the accumulation step.
authors.affiliation: GENOCOV Research Group, Departament d'Enginyeria Química, Biològica i Ambiental. Escola d'Enginyeria. Edifici Q, c/ de les Sitges S/N, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Montiel-Jarillo
authors.affiliation: GENOCOV Research Group, Departament d'Enginyeria Química, Biològica i Ambiental. Escola d'Enginyeria. Edifici Q, c/ de les Sitges S/N, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain.
authors.forename: Julián
authors.initials: J
authors.lastname: Carrera
authors.affiliation: GENOCOV Research Group, Departament d'Enginyeria Química, Biològica i Ambiental. Escola d'Enginyeria. Edifici Q, c/ de les Sitges S/N, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain. Electronic address: MariaEugenia.Suarez@uab.cat.
authors.forename: María Eugenia
authors.initials: ME
authors.lastname: Suárez-Ojeda
mesh_terms: D019149:Bioreactors / Q000382:microbiology*; D006863:Hydrogen-Ion Concentration; D059013:Microbial Consortia; D009584:Nitrogen / Q000032:analysis; D010758:Phosphorus / Q000032:analysis; D054813:Polyhydroxyalkanoates / Q000378:metabolism*; D014865:Waste Disposal, Fluid
chemical_list: D054813:Polyhydroxyalkanoates; D010758:Phosphorus; D009584:Nitrogen
keywords: Feast/famine; Mixed microbial cultures; Nutrients concentration; PHA; pH