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The effect of dissolved oxygen on PHB accumulation in activated sludge cultures.
Biotechnol Bioeng. 2003 Apr 20; 82(2):238-50.BB

Abstract

Nitrogen removal from wastewater is often limited by the availability of reducing power to perform denitrification, especially when treating wastewaters with a low carbon:nitrogen ratio. In the increasingly popular sequencing batch reactor (SBR), bacteria have the opportunity to preserve reducing power from incoming chemical oxygen demand (COD) as poly-beta-hydroxybutyrate (PHB). The current study uses laboratory experiments and mathematical modeling in an attempt to generate a better understanding of the effect of oxygen on microbial conversion of COD into PHB. Results from a laboratory SBR with acetate as the organic carbon source showed that the aerobic acetate uptake process was oxygen-dependent, producing higher uptake rates at higher dissolved oxygen (DO) supply rates. However, at the lower DO supply rates (k(L)a 6 to 16 h(-1), 0 mg L(-1) DO), a higher proportion of the substrate was preserved as PHB than at higher DO supply rates (k(L)a 30, 51 h(-1), DO >0.9 mg L(-1)). Up to 77% of the reducing equivalents available from acetate were converted to PHB under oxygen limitation (Y(PHB/Ac) 0.68 Cmol/Cmol), as opposed to only 54% under oxygen-excess conditions (Y(PHB/Ac) 0.48 Cmol/Cmol), where a higher fraction of acetate was used for biomass growth. It was calculated that, by oxygen management during the feast phase, the amount of PHB preserved (1.4 Cmmol L(-1) PHB) accounted for an additional denitrification potential of up to 18 mg L(-1) nitrate-nitrogen. The trends of the effect of oxygen (and hence ATP availability) on PHB accumulation could be reproduced by the simulation model, which was based on biochemical stoichiometry and maximum rates obtained from experiments. Simulated data showed that, at low DO concentrations, the limited availability of adenosine triphosphate (ATP) prevented significant biomass growth and most ATP was used for acetate transport into the cell. In contrast, high DO supply rates provided surplus ATP and hence higher growth rates, resulting in decreased PHB yields. The results suggest that oxygen management is crucial to conserving reducing power during the feast phase of SBR operation, as excessive aeration rates decrease the PHB yield and allow higher biomass growth.

Authors+Show Affiliations

Third KA
Division of Science and Engineering, School of Biological Sciences and Biotechnology, Murdoch University, South Street, Murdoch, WA 6150, Australia. kthird@murdoch.edu.au
Newland M
No affiliation info available
Cord-Ruwisch R
No affiliation info available

MeSH

AcetatesBacteria, AerobicBioreactorsComputer SimulationHydroxybutyratesIndustrial WasteModels, BiologicalOxygenOxygen ConsumptionPolyestersSewageWater Pollutants, ChemicalWater Purification

Pub Type(s)

Comparative Study
Evaluation Study
Journal Article
Validation Study

Language

eng

PubMed ID

12584766

Citation

Third, Katie A., et al. "The Effect of Dissolved Oxygen On PHB Accumulation in Activated Sludge Cultures." Biotechnology and Bioengineering, vol. 82, no. 2, 2003, pp. 238-50.
Third KA, Newland M, Cord-Ruwisch R. The effect of dissolved oxygen on PHB accumulation in activated sludge cultures. Biotechnol Bioeng. 2003;82(2):238-50.
Third, K. A., Newland, M., & Cord-Ruwisch, R. (2003). The effect of dissolved oxygen on PHB accumulation in activated sludge cultures. Biotechnology and Bioengineering, 82(2), 238-50.
Third KA, Newland M, Cord-Ruwisch R. The Effect of Dissolved Oxygen On PHB Accumulation in Activated Sludge Cultures. Biotechnol Bioeng. 2003 Apr 20;82(2):238-50. PubMed PMID: 12584766.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The effect of dissolved oxygen on PHB accumulation in activated sludge cultures. AU - Third,Katie A, AU - Newland,Mark, AU - Cord-Ruwisch,Ralf, PY - 2003/2/14/pubmed PY - 2003/9/27/medline PY - 2003/2/14/entrez SP - 238 EP - 50 JF - Biotechnology and bioengineering JO - Biotechnol Bioeng VL - 82 IS - 2 N2 - Nitrogen removal from wastewater is often limited by the availability of reducing power to perform denitrification, especially when treating wastewaters with a low carbon:nitrogen ratio. In the increasingly popular sequencing batch reactor (SBR), bacteria have the opportunity to preserve reducing power from incoming chemical oxygen demand (COD) as poly-beta-hydroxybutyrate (PHB). The current study uses laboratory experiments and mathematical modeling in an attempt to generate a better understanding of the effect of oxygen on microbial conversion of COD into PHB. Results from a laboratory SBR with acetate as the organic carbon source showed that the aerobic acetate uptake process was oxygen-dependent, producing higher uptake rates at higher dissolved oxygen (DO) supply rates. However, at the lower DO supply rates (k(L)a 6 to 16 h(-1), 0 mg L(-1) DO), a higher proportion of the substrate was preserved as PHB than at higher DO supply rates (k(L)a 30, 51 h(-1), DO >0.9 mg L(-1)). Up to 77% of the reducing equivalents available from acetate were converted to PHB under oxygen limitation (Y(PHB/Ac) 0.68 Cmol/Cmol), as opposed to only 54% under oxygen-excess conditions (Y(PHB/Ac) 0.48 Cmol/Cmol), where a higher fraction of acetate was used for biomass growth. It was calculated that, by oxygen management during the feast phase, the amount of PHB preserved (1.4 Cmmol L(-1) PHB) accounted for an additional denitrification potential of up to 18 mg L(-1) nitrate-nitrogen. The trends of the effect of oxygen (and hence ATP availability) on PHB accumulation could be reproduced by the simulation model, which was based on biochemical stoichiometry and maximum rates obtained from experiments. Simulated data showed that, at low DO concentrations, the limited availability of adenosine triphosphate (ATP) prevented significant biomass growth and most ATP was used for acetate transport into the cell. In contrast, high DO supply rates provided surplus ATP and hence higher growth rates, resulting in decreased PHB yields. The results suggest that oxygen management is crucial to conserving reducing power during the feast phase of SBR operation, as excessive aeration rates decrease the PHB yield and allow higher biomass growth. SN - 0006-3592 UR - https://www.unboundmedicine.com/medline/citation/12584766/The_effect_of_dissolved_oxygen_on_PHB_accumulation_in_activated_sludge_cultures_ DB - PRIME DP - Unbound Medicine ER -