Heterogeneous distribution of microbial activity in methanogenic aggregates : pH and glucose microprofiles

P.N.L. Lens, D. Beer, de, C.C.H. Cronenberg, F.P. Houwen, S.P.P. Ottengraf, W.H. Verstraete

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    Methanogenic aggregates, harvested from an upflow anaerobic sludge blanket reactor treating potato starch wastewater, were acclimatized to either glucose or a mixt. of sugars and org. nitrogen compds. (i.e., dild. molasses). Both types of granules exhibited internal pH and substrate concn. gradients in mineral medium (pH 7.0, 30 DegC), as was measured with microelectrodes. Glucose-acclimatized granules suspended in a mineral medium lacking glucose exhibited a distinct internal pH decrease of about 1 U within the granule, suggesting strong metab. by the acidogenic bacteria. Molasses-acclimatized and aged granules suspended in mineral medium did not exhibit such a pH decrease, suggesting the importance of the metabolic state of these acidogens. The pH gradient did not occur in deactivated granules and was not obsd. in strongly buffered media (mineral medium contg. 33 mM phosphate or reactor liq.). When glucose (0.5 to 5.0 mM) was added to the mineral medium, granules exhibited a convex pH profile. Glucose consumption was located exclusively in the outer 200 to 300 mm of the aggregates (mean diam. = 1.5 mm). The addn. of 20 mM 2-bromoethanesulfonic acid to the mineral medium indicated that the higher pH levels in the center of the granule appeared to be related to the activity of methanogens. It is suggested that acidogenic activity occurs predominantly in the outer 200 to 300 mm of the aggregate and methanogenic activity occurs predominantly in the center of the investigated granules. [on SciFinder (R)]
    Original languageEnglish
    Pages (from-to)3803-3815
    JournalApplied and Environmental Microbiology
    Issue number11
    Publication statusPublished - 1993

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