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Microbial degradation of lignin: how a bulky recalcitrant polymer is efficiently recycled in nature and how we can take advantage of this.

Ruiz-Dueñas FJ, Martínez AT - Microb Biotechnol (2009)

Bottom Line: Lignin is the second most abundant constituent of the cell wall of vascular plants, where it protects cellulose towards hydrolytic attack by saprophytic and pathogenic microbes.Ligninolytic microbes have developed a unique strategy to handle lignin degradation based on unspecific one-electron oxidation of the benzenic rings in the different lignin substructures by extracellular haemperoxidases acting synergistically with peroxide-generating oxidases.These peroxidases poses two outstanding characteristics: (i) they have unusually high redox potential due to haem pocket architecture that enables oxidation of non-phenolic aromatic rings, and (ii) they are able to generate a protein oxidizer by electron transfer to the haem cofactor forming a catalytic tryptophanyl-free radical at the protein surface, where it can interact with the bulky lignin polymer.

View Article: PubMed Central - PubMed

Affiliation: Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain. FJRuiz@cib.csic.es

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Three classical and two acylated lignin precursors or monolignols (top), and structural model for gymnosperm lignin (bottom). Gymnosperms produce the simplest lignin type formed only by guaiacyl units derived from coniferyl alcohol (2). In contrast, angiosperm lignin also include p‐hydroxyphenyl and sinapyl units derived from p‐coumaryl (1) and sinapyl (3) alcohols, as well as a variable amount of acylated lignin often derived from sinapyl alcohol γ‐esterified with acetic (4), p‐coumaric acid (5) or other organic acids (Ralph et al., 2004; Martínez et al., 2008). A variety of ether and carbon–carbon inter‐unit linkages are formed during monolignol radical polymerization resulting in β‐O‐4′ (A), phenylcoumaran (B), pinoresinol (C) and dibenzodioxocin (D) substructures, among others. Linkages to additional lignin chains are indicated (L‐containing circles). Other minor structures (in brackets) include vanillin, coniferyl alcohol and dimethylcyclohexadienone‐type units, the latter in new spirodienone substructures (Zhang et al., 2006) (courtesy of G. Gellerstedt).
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f1: Three classical and two acylated lignin precursors or monolignols (top), and structural model for gymnosperm lignin (bottom). Gymnosperms produce the simplest lignin type formed only by guaiacyl units derived from coniferyl alcohol (2). In contrast, angiosperm lignin also include p‐hydroxyphenyl and sinapyl units derived from p‐coumaryl (1) and sinapyl (3) alcohols, as well as a variable amount of acylated lignin often derived from sinapyl alcohol γ‐esterified with acetic (4), p‐coumaric acid (5) or other organic acids (Ralph et al., 2004; Martínez et al., 2008). A variety of ether and carbon–carbon inter‐unit linkages are formed during monolignol radical polymerization resulting in β‐O‐4′ (A), phenylcoumaran (B), pinoresinol (C) and dibenzodioxocin (D) substructures, among others. Linkages to additional lignin chains are indicated (L‐containing circles). Other minor structures (in brackets) include vanillin, coniferyl alcohol and dimethylcyclohexadienone‐type units, the latter in new spirodienone substructures (Zhang et al., 2006) (courtesy of G. Gellerstedt).

Mentions: Lignin is a complex aromatic polymer, highly recalcitrant towards both chemical and biological degradation, characteristic of the cell wall of vascular plants (Fig. 1). Around 20% of the total carbon fixed by photosynthesis in land ecosystems is incorporated into lignin, being the second main constituent of plant biomass after cellulose. In addition of providing plant stems the rigidity required for growth on land, and waterproofing vascular tissues for sap circulation, a main role of lignin is to protect the cellulose polymer towards hydrolytic attack by most pathogen and saprophytic organisms. In spite of this, lignin‐degrading microbes evolved simultaneously with the colonization of land by vascular plants in the Palaeozoic era, around 400 million year ago (Taylor and Osborne, 1996). Microbial degradation of lignin (Martínez et al., 2005; Kersten and Cullen, 2007) represents a key step for closing the carbon cycle, since removal of the lignin barrier enabled the subsequent use of plant carbohydrates by other microorganisms.


Microbial degradation of lignin: how a bulky recalcitrant polymer is efficiently recycled in nature and how we can take advantage of this.

Ruiz-Dueñas FJ, Martínez AT - Microb Biotechnol (2009)

Three classical and two acylated lignin precursors or monolignols (top), and structural model for gymnosperm lignin (bottom). Gymnosperms produce the simplest lignin type formed only by guaiacyl units derived from coniferyl alcohol (2). In contrast, angiosperm lignin also include p‐hydroxyphenyl and sinapyl units derived from p‐coumaryl (1) and sinapyl (3) alcohols, as well as a variable amount of acylated lignin often derived from sinapyl alcohol γ‐esterified with acetic (4), p‐coumaric acid (5) or other organic acids (Ralph et al., 2004; Martínez et al., 2008). A variety of ether and carbon–carbon inter‐unit linkages are formed during monolignol radical polymerization resulting in β‐O‐4′ (A), phenylcoumaran (B), pinoresinol (C) and dibenzodioxocin (D) substructures, among others. Linkages to additional lignin chains are indicated (L‐containing circles). Other minor structures (in brackets) include vanillin, coniferyl alcohol and dimethylcyclohexadienone‐type units, the latter in new spirodienone substructures (Zhang et al., 2006) (courtesy of G. Gellerstedt).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3815837&req=5

f1: Three classical and two acylated lignin precursors or monolignols (top), and structural model for gymnosperm lignin (bottom). Gymnosperms produce the simplest lignin type formed only by guaiacyl units derived from coniferyl alcohol (2). In contrast, angiosperm lignin also include p‐hydroxyphenyl and sinapyl units derived from p‐coumaryl (1) and sinapyl (3) alcohols, as well as a variable amount of acylated lignin often derived from sinapyl alcohol γ‐esterified with acetic (4), p‐coumaric acid (5) or other organic acids (Ralph et al., 2004; Martínez et al., 2008). A variety of ether and carbon–carbon inter‐unit linkages are formed during monolignol radical polymerization resulting in β‐O‐4′ (A), phenylcoumaran (B), pinoresinol (C) and dibenzodioxocin (D) substructures, among others. Linkages to additional lignin chains are indicated (L‐containing circles). Other minor structures (in brackets) include vanillin, coniferyl alcohol and dimethylcyclohexadienone‐type units, the latter in new spirodienone substructures (Zhang et al., 2006) (courtesy of G. Gellerstedt).
Mentions: Lignin is a complex aromatic polymer, highly recalcitrant towards both chemical and biological degradation, characteristic of the cell wall of vascular plants (Fig. 1). Around 20% of the total carbon fixed by photosynthesis in land ecosystems is incorporated into lignin, being the second main constituent of plant biomass after cellulose. In addition of providing plant stems the rigidity required for growth on land, and waterproofing vascular tissues for sap circulation, a main role of lignin is to protect the cellulose polymer towards hydrolytic attack by most pathogen and saprophytic organisms. In spite of this, lignin‐degrading microbes evolved simultaneously with the colonization of land by vascular plants in the Palaeozoic era, around 400 million year ago (Taylor and Osborne, 1996). Microbial degradation of lignin (Martínez et al., 2005; Kersten and Cullen, 2007) represents a key step for closing the carbon cycle, since removal of the lignin barrier enabled the subsequent use of plant carbohydrates by other microorganisms.

Bottom Line: Lignin is the second most abundant constituent of the cell wall of vascular plants, where it protects cellulose towards hydrolytic attack by saprophytic and pathogenic microbes.Ligninolytic microbes have developed a unique strategy to handle lignin degradation based on unspecific one-electron oxidation of the benzenic rings in the different lignin substructures by extracellular haemperoxidases acting synergistically with peroxide-generating oxidases.These peroxidases poses two outstanding characteristics: (i) they have unusually high redox potential due to haem pocket architecture that enables oxidation of non-phenolic aromatic rings, and (ii) they are able to generate a protein oxidizer by electron transfer to the haem cofactor forming a catalytic tryptophanyl-free radical at the protein surface, where it can interact with the bulky lignin polymer.

View Article: PubMed Central - PubMed

Affiliation: Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain. FJRuiz@cib.csic.es

Show MeSH
Related in: MedlinePlus