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Anaerobic and aerobic metabolism of glycogen-accumulating organisms selected with propionate as the sole carbon source

Adrian Oehmen

Raymond J. Zeng

Aaron M. Saunders

Advanced Wastewater Management Centre (AWMC), The University of Queensland, St Lucia, Brisbane 4072, Australia

Correspondence
Zhiguo Yuan
zhiguo{at}awmc.uq.edu.au

In the microbial competition observed in enhanced biological phosphorus removal (EBPR) systems, an undesirable group of micro-organisms known as glycogen-accumulating organisms (GAOs) compete for carbon in the anaerobic period with the desired polyphosphate-accumulating organisms (PAOs). Some studies have suggested that a propionate carbon source provides PAOs with a competitive advantage over GAOs in EBPR systems; however, the metabolism of GAOs with this carbon source has not been previously investigated. In this study, GAOs were enriched in a laboratory-scale bioreactor with propionate as the sole carbon source, in an effort to better understand their biochemical processes. Based on comprehensive solid-, liquid- and gas-phase chemical analytical data from the bioreactor, a metabolic model was proposed for the metabolism of propionate by GAOs. The model adequately described the anaerobic stoichiometry observed through chemical analysis, and can be a valuable tool for further investigation of the competition between PAOs and GAOs, and for the optimization of the EBPR process. A group of Alphaproteobacteria dominated the biomass (96 % of Bacteria) from this bioreactor, while post-fluorescence in situ hybridization (FISH) chemical staining confirmed that these Alphaproteobacteria produced poly--hydroxyalkanoates (PHAs) anaerobically and utilized them aerobically, demonstrating that they were putative GAOs. Some of the Alphaproteobacteria were related to Defluvicoccus vanus (16 % of Bacteria), but the specific identity of many could not be determined by FISH. Further investigation into the identity of other GAOs is necessary.

Present address: Lab. 505 - Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa (UNL), 2829-516 Caparica, Portugal.

Present address: Environment and Resources DTU, Bygningstorvet, bldg. 115, The Technical University of Denmark, DK - 2800 Lyngby, Denmark.

Present address: Department of Microbial Ecology, Aarhus University, Ny Munkegade, 8000 Aarhus C, Denmark.