Anoxic Biodegradation of Isosaccharinic Acids at Alkaline pH by Natural Microbial Communities

Simon P. Rout, Christopher J. Charles, Charalampos Doulgeris, Alan J. Mccarthy, Dave J. Rooks, J. Paul Loughnane, Andrew P. Laws, Paul N. Humphreys

Research output: Contribution to journalArticle

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Abstract

One design concept for the long-term management of the UK's intermediate level radioactive wastes (ILW) is disposal to a cementitious geological disposal facility (GDF). Under the alkaline (10.0<pH>13.0) anoxic conditions expected within a GDF, cellulosic wastes will undergo chemical hydrolysis. The resulting cellulose degradation products (CDP) are dominated by α- and β-isosaccharinic acids (ISA), which present an organic carbon source that may enable subsequent microbial colonisation of a GDF. Microcosms established from neutral, near-surface sediments demonstrated complete ISA degradation under methanogenic conditions up to pH 10.0. Degradation decreased as pH increased, with β-ISA fermentation more heavily influenced than α-ISA. This reduction in degradation rate was accompanied by a shift in microbial population away from organisms related to Clostridium sporosphaeroides to a more diverse Clostridial community. The increase in pH to 10.0 saw an increase in detection of Alcaligenes aquatilis and a dominance of hydrogenotrophic methanogens within the Archaeal population. Methane was generated up to pH 10.0 with acetate accumulation at higher pH values reflecting a reduced detection of acetoclastic methanogens. An increase in pH to 11.0 resulted in the accumulation of ISA, the absence of methanogenesis and the loss of biomass from the system. This study is the first to demonstrate methanogenesis from ISA by near surface microbial communities not previously exposed to these compounds up to and including pH 10.0.
Original languageEnglish
Article numbere0137682
JournalPLoS One
Volume10
Issue number9
DOIs
Publication statusPublished - 14 Sep 2015

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Biodegradation
biodegradation
microbial communities
acids
Methanogens
Degradation
methanogens
degradation
methane production
Radioactive waste disposal
Clostridium
Alcaligenes
Radioactive Waste
Waste Disposal Facilities
microbial colonization
Methane
Organic carbon
Cellulose
Fermentation
isosaccharinic acid

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Rout, Simon P. ; Charles, Christopher J. ; Doulgeris, Charalampos ; Mccarthy, Alan J. ; Rooks, Dave J. ; Loughnane, J. Paul ; Laws, Andrew P. ; Humphreys, Paul N. / Anoxic Biodegradation of Isosaccharinic Acids at Alkaline pH by Natural Microbial Communities. In: PLoS One. 2015 ; Vol. 10, No. 9.
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Anoxic Biodegradation of Isosaccharinic Acids at Alkaline pH by Natural Microbial Communities. / Rout, Simon P.; Charles, Christopher J.; Doulgeris, Charalampos; Mccarthy, Alan J.; Rooks, Dave J.; Loughnane, J. Paul; Laws, Andrew P.; Humphreys, Paul N.

In: PLoS One, Vol. 10, No. 9, e0137682, 14.09.2015.

Research output: Contribution to journalArticle

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AU - Rout, Simon P.

AU - Charles, Christopher J.

AU - Doulgeris, Charalampos

AU - Mccarthy, Alan J.

AU - Rooks, Dave J.

AU - Loughnane, J. Paul

AU - Laws, Andrew P.

AU - Humphreys, Paul N.

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AB - One design concept for the long-term management of the UK's intermediate level radioactive wastes (ILW) is disposal to a cementitious geological disposal facility (GDF). Under the alkaline (10.013.0) anoxic conditions expected within a GDF, cellulosic wastes will undergo chemical hydrolysis. The resulting cellulose degradation products (CDP) are dominated by α- and β-isosaccharinic acids (ISA), which present an organic carbon source that may enable subsequent microbial colonisation of a GDF. Microcosms established from neutral, near-surface sediments demonstrated complete ISA degradation under methanogenic conditions up to pH 10.0. Degradation decreased as pH increased, with β-ISA fermentation more heavily influenced than α-ISA. This reduction in degradation rate was accompanied by a shift in microbial population away from organisms related to Clostridium sporosphaeroides to a more diverse Clostridial community. The increase in pH to 10.0 saw an increase in detection of Alcaligenes aquatilis and a dominance of hydrogenotrophic methanogens within the Archaeal population. Methane was generated up to pH 10.0 with acetate accumulation at higher pH values reflecting a reduced detection of acetoclastic methanogens. An increase in pH to 11.0 resulted in the accumulation of ISA, the absence of methanogenesis and the loss of biomass from the system. This study is the first to demonstrate methanogenesis from ISA by near surface microbial communities not previously exposed to these compounds up to and including pH 10.0.

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Rout SP, Charles CJ, Doulgeris C, Mccarthy AJ, Rooks DJ, Loughnane JP et al. Anoxic Biodegradation of Isosaccharinic Acids at Alkaline pH by Natural Microbial Communities. PLoS One. 2015 Sep 14;10(9). e0137682. https://doi.org/10.1371/journal.pone.0137682