Complete Genome Sequence of Sphingobium sp. Strain YG1, a Lignin Model Dimer-Metabolizing Bacterium Isolated from Sediment in Kagoshima Bay, Japan

ABSTRACT Sphingobium sp. strain YG1 is a lignin model dimer-metabolizing bacterium newly isolated from sediment in Kagoshima, Japan, at a depth of 102 m. Here, we report the complete genome nucleotide sequence of strain YG1.

Degradation of a Phenolic β-O-4 Lignin Model Dimer by Electrochemically Mediated Delignification System with Violuric Acid

The β-O-4 type model compound guaiacylglycerol-β-guaiacyl ether was treated with a Violuric acid (VIO) mediated electrochemical delignification system. GC-MS analysis were used to investigate the changes of chemical structure of β-O-4 type model compound during reaction. Mechanism of this electrochemical delignification was also explored. Results indicated that the electrochemical oxidation by VIO as a mediator had strong oxidation capability on degradation of β-O-4 type model compound. After degradation, a series of aromatic compounds containing single benzene ring, furan compounds and aliphatic compounds with small molecule were produced. From their structures, the following reactions were caused by electrochemical oxidation: ether-bond cleavage, Cα-Cβ cleavage and benzene ring cleavage. Corrsequently, this work provides a comprehensive information on electrochemical oxidation delignification system that could be applied to industrial nonpollution bleaching.

Oxidative cleavage of non-phenolic β-O-4 lignin model dimers by an extracellular aromatic peroxygenase

The extracellular aromatic peroxygenase of the agaric fungusAgrocybe aegeritacatalyzed the H2O2-dependent cleavage of non-phenolic arylglycerol-β-aryl ethers (β-O-4 ethers). For instance 1-(3,4-dimethoxyphenyl)-2-(2-methoxy-phenoxy)propane-1,3-diol, a recalcitrant dimeric lignin model compound that represents the major non-phenolic substructure in lignin, was selectivelyO-demethylated at thepara-methoxy group to give formaldehyde and 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)propane-1,3-diol. The phenol moiety of the latter compound was then enzymatically oxidized into phenoxy radicals and a quinoid cation, which initiated the autocatalytic cleavage of the dimer and the formation of monomers such as 2-methoxy-1,4-benzoquinone and phenoxyl-substituted propionic acid. The introduction of18O from H218O2and H218O at different positions into the pro-ducts provided information about the routes of ether cleavage. Studies with a14C-labeled lignin model dimer showed that more than 70% of the intermediates formed were further coupled to form polymers with molecular masses above 10 kDa. The results indicate that fungal aromatic peroxygenases may be involved in the bioconversion of methoxylated plant ingredients originating from lignin or other sources.