Specific degradation of beta-aryl ether linkage in synthetic lignin (dehydrogenative polymerizate) by bacterial enzymes of Sphingomonas paucimobilis SYK-6 produced in recombinant Escherichia coli

Sphingomonas paucimobilis SYK-6 produces unique and specific enzymes, such as beta-etherases, O-demethylases, and ring fission dioxygenases, for lignin degradation. Cleavage of arylglycerol-beta-aryl ether linkage is the most important process in the lignin metabolic pathway of S. paucimobilis SYK-6. We reported the genes (ligD, ligE, ligF) for enzymes that cleaved beta-aryl ether linkage of dimeric compounds in previous studies. In this study we synthesized the fluorescent high-molecular-weight lignin (UBE-DHP) by dehydrogenative polymerization. We investigated the beta-aryl ether cleavage ability of these enzymes produced in recombinant Escherichia coli. When UBE-DHP was incubated with LigF, 4-methylumbeliferone was released as a result of beta-aryl ether cleavage of alpha-O-methylumbelliferyl-beta-hydroxypropiovanillone (compound III) incorporated in UBE-DHP. Here, we report that beta- etherase of S. paucimobilis SYK-6 can be expressed in E. coli and is able to cleave the beta-aryl ether linkage in synthetic high-molecular-weight lignin.