A metabolic model for acetate uptake under anaerobic conditions by glycogen accumulating organisms: Stoichiometry, kinetics, and the effect of pH

Effect of pH on the anaerobic acetate metabolism of biological phosphorus (P) removal processes was determined using anaerobic-aerobic activated sludge cultured with mainly acetate and containing a 12% or an 8% of total biomass as P (Px). The acetate uptake coupling to phosphate (Pi) release was found to be kinetically and thermodynamically influenced by pH. In the pH range 5.0–6.5, the acetate uptake rate (AUR) increased linearly with pH from 0 to about 50 (mg C/g VSS/h), and the Pi release rate (PiRR) from 20 to about 50 (mg P/g VSS/h). In the pH range 6.5–8.0, AUR remained at a constant range but PiRR continuously increased. Above pH 8.0, both AUR and PiRR started to decrease. With regard to the molar ratio of Pi released per acetate taken up (Pi/Ac), it was about 1.0 or 0.70–0.75 in the pH range 5.5–6.5, and proportionally increased to 1.75 or 1.50 in the pH range 6.6–8.5 for sludge containing a 12% Px or an 8% Px, respectively. Apparently, acidic pH inactivated the acetate metabolism, and basic pH stimulated too much Pi release, resulting an increase in energy consumption for acetate uptake (i.e. the Pi/Ac ratio). As a compromise, an optimum pH 6.8±0.7 was proposed for anaerobic acetate metabolism, because that a relatively high AUR with less energy consumption can be maintained by the bacteria that respond for biological P removal.

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Acetate uptake efficiency of polyphosphate-accumulating organisms under exposure to surfactants

Water Science & Technology ◽

10.2166/wst.2009.104 ◽

2009 ◽

Vol 60 (11) ◽

pp. 2775-2780

Author(s):

K. Tsuji ◽

M. Fujita ◽

H. Furumai

Keyword(s):

Municipal Wastewater ◽

Batch Reactor ◽

Alcohol Ethoxylates ◽

Anaerobic Conditions ◽

Linear Alkylbenzene ◽

Acetate Uptake ◽

Batch Tests ◽

Linear Alkylbenzene Sulfonates ◽

Negative Impacts ◽

Polyphosphate Accumulating Organisms

We investigated the influence of surfactants such as linear alkylbenzene sulfonates (LAS) and alcohol ethoxylates (AE) on acetate uptake by polyphosphate-accumulating organisms (PAOs) under anaerobic conditions, using the phosphate requirement for acetate uptake (+ΔP/−ΔAc ratio). In order to estimate the +ΔP/−ΔAc ratio, anaerobic batch tests were conducted using activated sludge collected from an anaerobic/oxic sequencing batch reactor used to treat municipal wastewater continuously supplemented with a detergent containing LAS and AE. We demonstrated that LAS and AE have both positive and negative impacts on acetate uptake by PAOs. The disadvantage is that long-term exposure to the detergent inhibits acetate uptake by PAOs, thus deteriorating the efficiency, even if the surfactants are no longer present during the tests. Furthermore, the existence of LAS and/or AE with acetate further diminishes the efficiency. The advantage is that LAS and AE are potential sources of polyhydroxyalkanoate for PAOs, because acetate is produced from the surfactants under anaerobic conditions.

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Effect of pH on Intracellular Accumulation of Trace Concentrations of Hg(II) in Escherichia coli under Anaerobic Conditions, as Measured Using a mer-lux Bioreporter

Applied and Environmental Microbiology ◽

10.1128/aem.00717-07 ◽

2007 ◽

Vol 74 (3) ◽

pp. 667-675 ◽

Cited By ~ 27

Author(s):

George R. Golding ◽

Richard Sparling ◽

Carol A. Kelly

Keyword(s):

Escherichia Coli ◽

Ph Effect ◽

Light Response ◽

Intracellular Accumulation ◽

Anaerobic Conditions ◽

Effect Of Ph ◽

Light Production ◽

Effects Of Ph ◽

Decreasing Ph ◽

Ph Range

ABSTRACT The effects of pH on the uptake and accumulation of Hg(II) by Escherichia coli were determined at trace, environmentally relevant, concentrations of Hg and under anaerobic conditions. Hg(II) accumulation was measured using inducible light production from E. coli HMS174 harboring a mer-lux bioreporter plasmid (pRB28). The effect of pH on the toxicity of higher concentrations of Hg(II) was measured using a constitutive lux plasmid (pRB27) in the same bacterial host. In this study, intracellular accumulation and toxicity of Hg(II) under anaerobic conditions were both significantly enhanced with decreasing pH over the pH range of 8 to 5. The pH effect on Hg(II) accumulation was most pronounced at pHs of <6, which substantially enhanced the Hg(II)-dependent light response. This enhanced response did not appear to be due to pH stress, as similar results were obtained whether cells were grown at the same pH as the assay or at a different pH. The enhanced accumulation of Hg(II) was also not related to differences in the chemical speciation of Hg(II) in the external medium resulting from the changes in pH. Experiments with Cd(II), also detectable by the mer-lux bioreporter system, showed that Cd(II) accumulation responded differently to pH changes than the net accumulation of Hg(II). Potential implications of these findings for our understanding of bacterial accumulation of Hg(II) under anaerobic conditions and for bacteria-mediated cycling of Hg(II) in aquatic ecosystems are discussed. Arguments are provided suggesting that this differential accumulation is due to changes in uptake of mercury.

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