Absence of microbial mineralization of lignin in anaerobic enrichment cultures

Odier, Étienne; Monties, Bernard

doi:10.1128/aem.46.3.661-665.1983

Cited by 38 publications

(8 citation statements)

References 27 publications

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“…The ¢ndings of this study suggest that the ability to cleave benzyl ether bonds by the rumen microbes could include high molecular mass lignin polymers as long as they are phenolic, but might be restricted to dimers when they are non-phenolic. The amount of cleaved benzyl ether lignin bonds in the rumen that we observed is high, as previous reports [20,21] indicated that anaerobic biodegradation of high molecular mass lignins required a much longer time (over 100 days).…”

Section: Discussionsupporting

confidence: 83%

Degradation of benzyl ether bonds of lignin by ruminal microbes

Kajikawa

Kudo

Kondo

et al. 2000

FEMS Microbiology Letters

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We examined microbial activity in the rumen to cleave benzyl ether bonds of lignin model compounds that fluoresced when the bonds were cleaved. 4-Methylumbelliferone veratryl ether dimer was degraded completely within 8 h even in the presence of fungicidal antibiotics, but no significant degradation occurred with bactericidal antibiotics. Degradation of a phenolic beta-O-4 trimer incorporating 4-methylumbelliferone by a benzyl ether linkage was stimulated by ruminal microbes, although its corresponding non-phenolic model compound, 1-(4-ethoxy-3-methoxyphenyl)-1-O-(4-methylumbelliferyl)-2-(2-methoxyp henoxy)-3-propanol, was not degraded. A coniferyl dehydrogenation polymer bearing fluorescent beta-O-4 benzyl ether that contains both phenolic and non-phenolic benzyl ether bonds was partially degraded (about 20%) in 48 h. These results suggest that ruminal microbes decompose benzyl ether linkages of lignin polymers under anaerobic conditions.

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Section: Discussionsupporting

confidence: 83%

Degradation of benzyl ether bonds of lignin by ruminal microbes

Kajikawa

Kudo

Kondo

et al. 2000

FEMS Microbiology Letters

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“…Could the decomposition of such aromatic compounds account for the apparent CO 2 :CH 4 imbalance? The earliest studies suggested that lignin was resistant to decomposition in the absence of O 2 (Hackett et al 1977;Zeikus et al 1982;Odier and Monties 1983), but later work reported that limited anaerobic degradation of lignin is possible under some conditions-particularly in the presence of sulfate or nitrate as electron acceptors (Kaiser and Hanselmann, 1982;Benner et al 1984;Colberg and Young 1985). However, very little was known about the mechanism of anaerobic decomposition of lignin-like compounds until recent studies demonstrated that the major lignin-derived aromatic compounds-syringate and vanillate-also produce equimolar CO 2 :CH 4 under TEA-limited, methanogenic conditions (Kato et al 2015).…”

Section: (Equation 3)mentioning

confidence: 99%

Hydrogenation of organic matter as a terminal electron sink sustains high CO2:CH4 production ratios during anaerobic decomposition

Wilson

Tfaily

Rich

et al. 2017

Organic Geochemistry

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Once inorganic electron acceptors are depleted, organic matter in anoxic environments decomposes by hydrolysis, fermentation, and methanogenesis, requiring syntrophic interactions between microorganisms to achieve energetic favorability. In this classic anaerobic food chain, methanogenesis represents the terminal electron accepting (TEA) process, ultimately producing equimolar CO 2 and CH 4 for each molecule of organic matter degraded. However, CO 2 :CH 4 production in Sphagnum-derived, mineral-poor, cellulosic peat often substantially exceeds this 1:1 ratio, even in the absence of measureable inorganic TEAs. Since the oxidation state of C in both cellulose-derived organic matter and acetate is 0, and CO 2 has an oxidation state of +4, if CH 4 (oxidation state -4) is not produced in equal ratio, then some other compound(s) must balance CO 2 production by receiving 4 electrons. Here we present evidence for ubiquitous hydrogenation of diverse unsaturated compounds that appear to serve as organic TEAs in peat, thereby providing the necessary electron balance to sustain CO 2 :CH 4 >1. While organic electron acceptors have previously been proposed to drive microbial respiration of organic matter through the reversible reduction of quinone moieties, the hydrogenation mechanism that we propose, by contrast, reduces C-C double bonds in organic matter thereby serving as 1) a terminal electron sink, 2) a mechanism for degrading complex unsaturated organic molecules, 3) a potential mechanism to regenerate electron-accepting quinones, and, in some cases, 4) a means to alleviate the toxicity of unsaturated aromatic acids. This mechanism for CO 2 generation without concomitant CH 4 production has the potential to regulate the global warming potential of peatlands by elevating CO 2 :CH 4 production ratios.

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“…1. The 14C label is likely to have been incorporated chiefly into such exposed, less-condensed units during the short maturation of 72 h after the administration of the labeled precursors (14,48), resulting in the formation of more easily degradable lignocelluloses (1,32).…”

Section: Mineralization Of [14cjlignocelluloses Release Of 14co2mentioning

confidence: 99%

Decomposition of [ ¹⁴ C]Lignocelluloses of Spartina alterniflora and a Comparison with Field Experiments

Wilson

1985

Appl Environ Microbiol

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Decomposition of lignocelluloses from Spartina alterniflora in salt-marsh sediments was measured by using 14C-labeled compounds. Rates of decomposition were fastest in the first 4 days of incubation and declined later. Lignins labeled in side chains were mineralized slightly faster than uniformly labeled lignins; 12% of the [side chain-14C]lignin-labeled lignocellulose was mineralized after 816 h of incubation, whereas only 8% of the [U-14C]lignin-labeled lignocelluloses were degraded during this period. The carbohydrate moiety within the lignocellulose complex was degraded about four times faster than the lignin moiety; after 816 h of incubation, 29 to 37% of the carbohydrate moiety had been mineralized. Changes in concentration of lignin and cellulose in litter of S. alterniflora were followed over 2 years of decay. CeDlulose disappeared from litter more rapidly than lignin; 50% of the initial content of cellulose was lost after 130 days, whereas lignin required 330 to 380 days for 50% loss. The slow loss of lignin compared with other litter components resulted in a progressive

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Absence of microbial mineralization of lignin in anaerobic enrichment cultures

Cited by 38 publications

References 27 publications

Degradation of benzyl ether bonds of lignin by ruminal microbes

Degradation of benzyl ether bonds of lignin by ruminal microbes

Hydrogenation of organic matter as a terminal electron sink sustains high CO2:CH4 production ratios during anaerobic decomposition

Decomposition of [ ¹⁴ C]Lignocelluloses of Spartina alterniflora and a Comparison with Field Experiments

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Absence of microbial mineralization of lignin in anaerobic enrichment cultures

Cited by 38 publications

References 27 publications

Degradation of benzyl ether bonds of lignin by ruminal microbes

Degradation of benzyl ether bonds of lignin by ruminal microbes

Hydrogenation of organic matter as a terminal electron sink sustains high CO2:CH4 production ratios during anaerobic decomposition

Decomposition of [ 14 C]Lignocelluloses of Spartina alterniflora and a Comparison with Field Experiments

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Decomposition of [ ¹⁴ C]Lignocelluloses of Spartina alterniflora and a Comparison with Field Experiments