刊行物

刊行物
(Lignin)
Vol.3(2022)
Original article
4-Hydroxybenzoic Acid Secreted from Trametes versicolor Catalyzes the Oxidation of a Nonphenolic β-O-4 Lignin Model Dimer as Laccase Mediator

Shingo Kawai, Megumi Miyazaki, Yoshimi Hayashi, Miyuki Matsunaga, Haruka Hirashita, Tomoaki Nishida, Yuko Yoneda
Pages: 1-8
Published online: 17 May 2022

Abstract: To detect natural laccase mediator, the extracellular culture fluid of Trametes versicolor laccase production medium was fractionated using degradation of anthracene which can not be degraded with laccase alone. As a result, 4-hydroxybenzoic acid (HBA) was isolated from the culture fluid, and it was clear that HBA acted as a natural mediator and the degradation efficiency of anthracene by laccase greatly increased. The laccase-HBA system could also oxidized the nonphenolic β-O-4 lignin model dimer to pruduce the Cα-oxidation, β-ether cleavage and aromatic ring cleavage products. The oxidation mechanisms of the laccase-HBA system are very similar to those for lignin peroxidase and laccase-1-hydroxybenzotriazol (HBT) system.
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Review Article
Bacterial Catabolism of a Lignin-derived β–5 Dimer

Naofumi Kamimura, Eiji Masai
Pages: 9-14
Published online: 26 Aug 2022

Abstract: The β–5 linkage is an intermolecular linkage in lignin. Sphingobium sp. strain SYK-6 can assimilate various lignin-derived dimers, including a β–5 dimer, dehydrodiconiferyl alcohol. In SYK-6, the hydroxyl group at Cγ of the B-ring side chain of dehydrodiconiferyl alcohol is oxidized to generate the γ-carboxylic compound, DCA-C. Then, the hydroxyl group at Cγ of the A-ring side chain of DCA-C is oxidized to the carboxyl group to generate the dicarboxylic compound, DCA-CC. The carboxylic group at Cγ of the A-ring side chain of DCA-CC is decarboxylated, and the accompanying spontaneous ether cleavage of the coumaran ring produces a stilbene-type compound, DCA-S. The conversions of DCA-C and DCA-CC are catalyzed by enantiospecific oxidases (PhcC and PhcD) and enantiospecific decarboxylases (PhcF and PhcG), respectively. DCA-S is subjected to cleavage of the interphenyl double bond by lignostilbene α,β-dioxygenase to generate 5-formylferulate and vanillin. Among the eight lignostilbene α,β-dioxygenase genes, vanillate-induced lsdD plays a critical role in cleaving DCA-S. The formyl group of 5-formylferulate is oxidized, and the resultant carboxylic group is subsequently decarboxylated to produce ferulate. Finally, ferulate and vanillin are further catabolized via a previously characterized pathway.
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