Oxidation of non‐phenolic substrates

Abstract

In the presence of substrates such as Remazol Blue and 2,2'-azlnobls(3-ethylbenzthiazoline-6-sulphonate) (ABTS), laccases Cor~olus / Trumeterj vers~olor can also oxidize non-phenolic lignm model compounds Veratryl alcohol (I) and 1-(3,4-dlmethoxyphenyl)-2-(2-methoxyphenoxy)-propane-1.3-dtol (III) were oxtdized by lactase and medrator to give the a-carbonyl derivativesThe p-1 hgnin model dtmer, 1-(3,4-dimethoxyphenyl)-2-phenoxy-ethane-I ,2-dtol (II) was cleaved by lactase in the presence of ABTS to give veratraldehyde and benzaldehyde. On the basis of these observations, we propose that lactase is capable of oxidizing both phenolic and non-phenohc moieties of hgnm but that the latter is dependent on the co-presence of prtmary lactase substrates

The early oxidative biodegradation steps of residual kraft lignin models with laccase

“…In fact, it has been reported that the radical mediator ABTS is able to bring about the oxidation of non-phenolic systems characterized by a redox potential higher than laccase such as veratryl alcohol or non-phenolic b-O-4 model compounds. 3 In contrast, recent ®ndings have also shown that the reactivity of benzylic alcohols in the presence of the laccase-mediator system depends on the substitution pattern on the aromatic ring. 18,23 In particular, 2,6-disubstituted benzylic alcohols were found to be unreactive with the laccase-mediator system.…”

“…2 In order to elucidate the deligni®cation mechanism catalyzed by laccase, several studies have been carried out on both phenolic and non-phenolic monomeric, arylglycerol b-O-4 and b-1 ether lignin model compounds. 3±5 The use of radical mediators has become of interest since the early report that non-phenolic lignin model compounds, unreactive towards laccase alone, could be oxidized in the presence of laccase and ABTS, 3 and that kraft pulp could be deligni®ed. Since then, 1-hydroxybenzotriazole was found to mediate pulp deligni®cation in the presence of laccase.…”

Laccase is essential for lignin degradation by the white‐rot fungus Pycnoporus cinnabarinus

“…For a long time, laccase was not considered as an enzyme suitable for the complete oxidation of lignin because of the low redox potential of the enzyme that did not allow for oxidation of non-phenolic lignin structures. However, Bourbonnais and Paice [8] showed that the artificial laccase substrate ABTS could act as a redox mediator which enabled laccase to oxi-*Corresponding author. Fax: (1) (706) 542-2222.…”

`Yellow' laccase of Panus tigrinus oxidizes non‐phenolic substrates without electron‐transfer mediators

“…The ligninolytic potential of fungal laccases was evaluated rarely because laccase does not oxidize non-phenolic structures which are predominant in lignin. However, it was found that the Coriolus versicolor laccase oxidized non-phenolic compounds in the presence of aromatic electron-transfer mediators [4].…”