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Title: The effect of mild acid stress on environmental microorganisms
Author: MacCombe, Diane Martha Elizabeth
ISNI:       0000 0001 3614 8865
Awarding Body: Queen's University of Belfast
Current Institution: Queen's University Belfast
Date of Award: 2008
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The requirement to reduce biomass production & enhance polyphosphate production during the wastewater treatment process is necessary to ensure the process is environmentally sound & cost effective. The effect of mildly acidic pH (pH6.0) on . the biomass formation & polyphosphate production by a range ofenvironmental microorganisms was investigated, using activated sludge from a trial wastewater treatment plant & a range ofenvironmental isolates. Activated sludge obtained from a treatment plant operating at pH6.0, produced lower levels of biomass alongside a higher level ofphosphate removal & higher rates ofrespiration & substrate utilisation, compared to operation ofthe same plant at higher operational pH levels. Seven pure culture isolates were also characterised in terms of their phosphate removal & biomass yields over a range ofpH values (5-.5 to 7.5). Isolates could be identified as members ofone Qfthe following: (1) demonstrate reduced biomass yields & accumulate more polyphosphate at an acidic pH, e.g. Erwinia carotovora subsp. atroseptica, (2) exhibit reduced biomass yields & polyphosphate accumulation at acidic pH e.g. Pseudomonf:ls aeruginosa PAOl, and (3) display similar or higher biomass yields at acidic pH & accumulate higher levels ofpolyphosphate at these acidic pH levels, e.g. Burkholderia cepacia AM19. Three microorganisms were studied further in continuous culture at pH6.0. E. carotovora displayed lower levels of biomass yield coupled with higher substrate utilisation rates, ATP formation rates & total intracellular P levels. B. cepacia AM19 & P. aeruginosa PAOl, in contrast displayed similar levels ofbiomass production, P removal & substrate utilisation rates. The response by E. carotovorG&activated sludge to acidic pH would suggest an increase in maintenance energy at acidic pH, caused by an increased rate ofproton pumping in order to maintain a constant intracellular pH with polyphosphate playing a protective role at acidic pH.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available