The emerging role for bacteria in lignin degradation and bio-product formation

Bugg, Timothy D. H.; Ahmad, Masroor; Hardiman, Elizabeth M.; Singh, Rahul

doi:10.1016/j.copbio.2010.10.009

Cited by 652 publications

(506 citation statements)

References 43 publications

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“…[5][6][7] These enzymes could be valuable biocatalysts for the valorisation of lignin produced as a byproduct of biofuel production and pulp/paper manufacture, including Kraft lignin for which the SpMnSOD enzymes show activity. 4 The identification of reaction products from oxidation of polymeric lignin helps to define further the metabolic pathways for microbial lignin breakdown. 20…”

Section: Figure 7 Hypotheses For Generation Of Lignin Oxidant By Mnsodmentioning

confidence: 99%

Identification of Manganese Superoxide Dismutase from Sphingobacterium sp. T2 as a Novel Bacterial Enzyme for Lignin Oxidation

et al. 2015

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Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work of researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-forprofit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher's statement:This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Chemical Biology, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see: http://dx.doi.org/10.1021/acschembio.5b00298The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription. centre ligated by three His, one Asp and a water/hydroxide in each active site. We propose that the lignin oxidation reactivity of these enzymes is due to the production of hydroxyl radical, a highly reactive oxidant. This is the first demonstration that MnSOD is a microbial lignin-oxidising enzyme.3

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Section: Figure 7 Hypotheses For Generation Of Lignin Oxidant By Mnsodmentioning

confidence: 99%

Identification of Manganese Superoxide Dismutase from Sphingobacterium sp. T2 as a Novel Bacterial Enzyme for Lignin Oxidation

et al. 2015

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“…isolated from terrestrial and aquatic systems can do so as well (18,19). Despite the widespread physiological potential for microbial Mn oxidation, it is unclear to what extent the natural Mn redox cycle is coupled to organic matter degradation in forest ecosystems.…”

Section: Significancementioning

confidence: 99%

Long-term litter decomposition controlled by manganese redox cycling

Keiluweit

Nico

Harmon

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

179

156

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Litter decomposition is a keystone ecosystem process impacting nutrient cycling and productivity, soil properties, and the terrestrial carbon (C) balance, but the factors regulating decomposition rate are still poorly understood. Traditional models assume that the rate is controlled by litter quality, relying on parameters such as lignin content as predictors. However, a strong correlation has been observed between the manganese (Mn) content of litter and decomposition rates across a variety of forest ecosystems. Here, we show that long-term litter decomposition in forest ecosystems is tightly coupled to Mn redox cycling. Over 7 years of litter decomposition, microbial transformation of litter was paralleled by variations in Mn oxidation state and concentration. A detailed chemical imaging analysis of the litter revealed that fungi recruit and redistribute unreactive Mn 2+ provided by fresh plant litter to produce oxidative Mn 3+ species at sites of active decay, with Mn eventually accumulating as insoluble Mn 3+/4+ oxides. Formation of reactive Mn 3+ species coincided with the generation of aromatic oxidation products, providing direct proof of the previously posited role of Mn 3+ -based oxidizers in the breakdown of litter. Our results suggest that the litter-decomposing machinery at our coniferous forest site depends on the ability of plants and microbes to supply, accumulate, and regenerate short-lived Mn 3+ species in the litter layer. This observation indicates that biogeochemical constraints on bioavailability, mobility, and reactivity of Mn in the plant-soil system may have a profound impact on litter decomposition rates.terrestrial carbon cycle | nutrient cycling | forest soil ecosystems | soil-atmosphere interactions | climate change D ecomposition of above-ground plant detritus (litter) is a fundamental process regulating the release of nutrients for plant growth and the formation of soil organic matter (SOM) in forest ecosystems (1). Litter decomposition regulates the proportion of litter-derived carbon (C) that is either retained in the system as SOM or lost as CO 2 (2), thereby influencing net C storage in soils. Although even small decomposition rate increases may accelerate climate change by virtue of increasing CO 2 emissions from soils (3), uncertainty persists over the ratecontrolling mechanisms (4, 5).Litter decomposition rates are strongly influenced by climatic factors (e.g., temperature and moisture) and have long been linked to litter chemistry, specifically lignin content (6). Ligninan aromatic biopolymer-often makes up between 15% and 40% of the litter mass and is concentrated in cell walls (7). It encrusts cellulose microfibrils to form protective physical units ("ligno-cellulose complexes") that are embedded in a matrix of hemicellulose. Conventional thinking suggests that the relatively high initial litter decomposition rates are due to the preferential use of soluble and readily accessible polysaccharides and hemicelluloses relative to lignin components. In later stages, decompositi...

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“…Thus, depolymerization of unprocessed lignin remains of significant interest 8,16 and has been pursued experimentally with polyoxometalate catalysts 17 , base-catalyzed hydrolysis [18][19] , acidolysis [20][21] , ionic liquid treatment 22 , reduction with hydrosilanes 23 , photochemical degradation 24 , and ball milling 25 . In addition to general depolymerization, efforts have also included selective strategies via homogeneous catalysts [26][27][28][29][30] and enzymes 31 . A route to selective depolymerization that both prevents repolymerization and generates a specific set of monomers 32 has only recently had success with the aid of metal catalysts [33][34] capable of producing up to 50% yield.…”

Section: Introductionmentioning

confidence: 99%

Depolymerization Pathways for Branching Lignin Spirodienone Units Revealed with ab Initio Steered Molecular Dynamics

Mar

Kulik

2017

J. Phys. Chem. A

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Lignocellulosic biomass is an abundant, rich source of aromatic compounds, but direct utilization of raw lignin has been hampered by both the high heterogeneity and variability of linking bonds in this biopolymer. Ab initio steered molecular dynamics (AISMD) has emerged both as a fruitful direct computational screening approach to identify products that occur through mechanical depolymerization (i.e., in sonication or ball-milling) and as a sampling approach. By varying the direction of force and sampling over 750 AISMD trajectories, we identify numerous possible pathways through which lignin depolymerization may occur in pyrolysis or through catalytic depolymerization as well. Here, we present eight unique major depolymerization pathways discovered via AISMD for the recently characterized spirodienone lignin branchinglinkage that may comprise around 10% weight of all lignin in some softwoods. We extract representative trajectories from AISMD and carry out reaction pathway analysis to identify energetically favorable pathways for lignin depolymerization. Importantly, we identify dynamical effects that could not be observed through more traditional calculations of bond dissociation energies. Such effects include thermodynamically favorable recovery of aromaticity in the dienone ring that leads to near-barrierless subsequent ether cleavage and hydrogen bonding effects that stabilize newly formed radicals. Some of the most stable spirodienone fragments that reside at most 1 eV above the reactant structure are formed with only 2 eV barriers for C-C bond cleavage, suggesting key targets for catalyst design to drive targeted depolymerization of lignin.2

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The emerging role for bacteria in lignin degradation and bio-product formation

Cited by 652 publications

References 43 publications

Identification of Manganese Superoxide Dismutase from Sphingobacterium sp. T2 as a Novel Bacterial Enzyme for Lignin Oxidation

Identification of Manganese Superoxide Dismutase from Sphingobacterium sp. T2 as a Novel Bacterial Enzyme for Lignin Oxidation

Long-term litter decomposition controlled by manganese redox cycling

Depolymerization Pathways for Branching Lignin Spirodienone Units Revealed with ab Initio Steered Molecular Dynamics

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