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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Original article
Optimization of Alkaline Hydrogen Peroxide Treatment of Lignin Model Compound at High pH Levels for Producing Aromatic Aldehyde and Acid as Fine Chemicals

Tatsuyuki Sakai, Kyoko S. Katsumata, Tomoya Yokoyama
Pages: 15-25
Published online: 28 December 2022

Abstract: A non-phenolic β-O-4-type lignin model compound, veratrylglycerol-β-guaiacyl ether (VG), was treated with H2O2 at high pH levels in our previous study. Veratraldehyde (Vald) and veratric acid (Vacid), which are non-phenolic analogues of the most common lignin-based fine chemicals, vanillin and vanillic acid, respectively, were obtained with a high total yield of 77% based on the amount of degraded VG, although only 22% of VG was degraded and hence the total yield of Vald and Vacid was only 17% based on the initial amount of VG. This study optimized the alkaline H2O2 treatment to enhance the degradation of VG and yields of Vald and Vacid. The degradation of VG and total yield of Vald and Vacid were enhanced from 22% to 54% and from 17% to 39%, respectively, by optimizing the conditions as follows: 1.96 mmol of H2O2 were added stepwise 400 times with an interval of 15 s in a reaction solution containing 1.0 mmol/L VG, 3.0 mol/L NaOH, 1.08 mmol/L FeCl3, and 3.24 mmol/L mannitol at 90℃. Doubling the reaction period and employing twice the amount of H2O2 (3.92 mmol) in the absence of mannitol further enhanced the degradation of VG to 61% and the total yield to 44%.
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