Lignin substructure model compounds

Next to 3-0-4 lignin substructure model compounds, 3-1 lignin substructure model compounds have been often used for lignin biodegradation studies. This type of compound was found to be degraded... 

Figure 1. 3-0-4 lignin substructure model compounds and products of their degradation by ligninolytic cultures of Phanerochaete chrysosporium and by lignin peroxidase. D H, and 0 of 3-ether bond and of H2 0, respectively. B and C show results of stable isotope experiments. 

Aromatic Ring Cleavage of Nonphenolic 0-0-4 Lignin Substructure Model Compounds and Veratryl Alcohol by Lignin Peroxidase. 

Lignin peroxidase of Phanerochaete chrysosporium catalyzes the ring cleavage of /3-0-4 lignin substructure model compounds and synthetic lignin (DHP). A mechanism for the ring cleavage by the enzyme is described. 

The purpose of the present paper is to describe the aromatic ring cleavage of lignin substructure model compounds by white-rot basidiomycetes and by lignin peroxidase of P. chrysosporium. The aromatic ring cleavage of synthetic lignin (DHP) by the enzyme will also be described. 

S Kawai, T Umezawa, T Fliguchi. Degradation mechanisms of phenolic beta-1 lignin substructure model compounds by laccase of Coriolus versicolor. Arch. Biochem. Biophys. 262(1) 99-110, 1988. 

Also obtained from l,2-bis(4-hydroxy-3,5-dimethoxyphenyl)-propane-l,3-diol, a P-1-lignin substructure model compound, by degradation with laccase of... 

For lignin substructures containing a carbon substituent in the aromatic C-5 position, or for stilbenes originating from phenylcoumaran structures, the oxidative degradation leads to the formation of isohemipinic acid methyl ester (4) (Fig. 6.3.2, R=CH3). However, Gellerstedt and co-workers have shown that model compounds of the biphenyl type also give rise to isohemipinic acid in addition to the expected bis-vanillic acid structure (7). The reason seems to be incomplete alkylation (pH 11, 24 h) with the result that the substrate is alkylated at only one of the available positions. To achieve a more complete alkylation, it is necessary to increase the pH to 13 or alternatively, to extend the alkylation time to 84 h. In both cases, the yield of the bis-vanillic acid structure is substantially increased as shown in Table 6.3.1 nevertheless, the concomitant formation of isohemipinic acid cannot be completely avoided. 

S Kawai, M Asukai, N Ohya, K Okita, T Ito, H Ohashi. Degradation of a non-phe-nolic beta-O-4 substructure and of polymeric lignin model compounds by laccase of Coriolus versicolor in the presence of 1-hydroxybenzotriazole. FEMS Microbiol. Lett. 170(l) 51-57, 1999. 

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