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Microb Biotechnol. 2009 Mar;2(2):164-77. doi: 10.1111/j.1751-7915.2008.00078.x. Epub 2009 Jan 13.

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

Author information

1
Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, E-28040 Madrid, Spain. FJRuiz@cib.csic.es

Abstract

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. Its removal represents a key step for carbon recycling in land ecosystems, as well as a central issue for industrial utilization of plant biomass. The lignin polymer is highly recalcitrant towards chemical and biological degradation due to its molecular architecture, where different non-phenolic phenylpropanoid units form a complex three-dimensional network linked by a variety of ether and carbon-carbon bonds. 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. The structure-function information currently available is being used to build tailor-made peroxidases and other oxidoreductases as industrial biocatalysts.

PMID:
21261911
PMCID:
PMC3815837
DOI:
10.1111/j.1751-7915.2008.00078.x
[Indexed for MEDLINE]
Free PMC Article

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