The extracellular fluid of ligninolytic cultures of the wood-decomposing basidiomycete Phanerochaete chrysosporium Burds. contains an enzyme that degrades lignin substructure model compounds as well as spruce and birch lignins. It has a molecular size of 42,000 daltons and requires hydrogen peroxide for activity.

https://science.sciencemag.org/content/sci/221/4611/661.full.pdf

Lignin-Degrading Enzyme from the Hymenomycete Phanerochaete chrysosporium Burds.

Pathways for degradation of lignin in bacteria and fungi

Lignin in straw of herbaceous crops

(Received 17 October 2000/Accepted 12 April 2001) The sources of ligninocellulose that occur in various forms in nature are so vast that they can only be compared to those of water. The results of several, more recent experiments showed that laccase probably possesses the big ability for "lignin-barrier" breakdown of ligninocellulose. The degradation of this compound is currently understood as an enzymatic process mediated by small molecules, therefore, this review will focus on the role of these mediators and radicals working in concert with enzymes. The fungi having a versatile machinery of enzymes are able to attack directly the "lignin- barrier" or can use a multienzyme system including "feed-back" type enzymes allowing for simulta- neous transformation of lignin and carbohydrate compounds.

Fungal laccase: properties and activity on lignin

Extensive research efforts have been dedicated to describing degradation of wood, which is a complex process; hence, microorganisms have evolved different enzymatic and non-enzymatic strategies to utilize this plentiful plant material. This review describes a number of fungal and bacterial organisms which have developed both competitive and mutualistic strategies for the decomposition of wood and to thrive in different ecological niches. Through the analysis of the enzymatic machinery engaged in wood degradation, it was possible to elucidate different strategies of wood decomposition which often depend on ecological niches inhabited by given organism. Moreover, a detailed description of low molecular weight compounds is presented, which gives these organisms not only an advantage in wood degradation processes, but seems rather to be a new evolutionatory alternative to enzymatic combustion. Through analysis of genomics and secretomic data, it was possible to underline the probable importance of certain wood-degrading enzymes produced by different fungal organisms, potentially giving them advantage in their ecological niches. The paper highlights different fungal strategies of wood degradation, which possibly correlates to the number of genes coding for secretory enzymes. Furthermore, investigation of the evolution of wood-degrading organisms has been described.

Lignin degradation: microorganisms, enzymes involved, genomes analysis and evolution.

Spruce wood was pre-extracted, decayed with the white-rot fungus Phanerochaete chrysosporium to a 20% loss in lignin content, and then extracted successively with solvents of increasing polarity (pet. ether, chloroform, acetone, methanol, and aqueous dioxane). The methanol extract (0.5% of the decayed wood) was divided into acid and phenol fractions, and these further into high and low molecular weight components. The low molecular weight acid fraction was examined by high performance liquid chromatography and, after acetylation and methylation, by gas chromatography/mass spectrometry. The following compounds were identified: 4-hydroxybenzoic acid (I), vanillic acid (2), isovanillic acid (3), veratric acid (4), 4-hydroxy- 5-methoxyphthalic acid (7), m-hemipinic acid (8), dehydrodivanillic acid (9), and 2'-hydroxy-2,3'-dimethoxydiphenylether-4,5'- dicarboxylic acid (10), 4-Hydroxy-3-methoxymandelic acid (11) was also tentatively identified. Compounds 2, 3, 4, 8, and 9 were the most abundant. Vanillic acid (2), homovanillic acid, and acetovanillone were 4-O-methylated by ligninolytic cultures of Ph. chrysosporium, with methionine serving as methyl donor. Thus compounds 4, 6, and 8 (and possibly 3), containing 4-O-methyl groups, probably arose via fungal methylation. Results establish that lignin is degraded by white-rot fungi in part via low molecular weight aromatic acids, formation of which involves C alpha-C beta side chain cleavage with C alpha oxidation. (Refs. 32).

T.K. Kirk

Papers

Aromatic acids produced during degradation of lignin in spruce wood by Phanerochaete chrysosporium