Oxidation of guaiacyl- and veratryl-glycerol-β-guaiacyl ether by polyporus versicolor and stereum frustulation

• Published in: Biochimica et biophysica acta. General subjects Vol. 165; no. 1; pp. 134 - 144
• Main Authors: Kirk, T.Kent, Hapkin, John M., Cowling, Ellis B.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 06.08.1968
• ISSN: 0304-4165; 1872-8006
• DOI: 10.1016/0304-4165(68)90198-0

1. 1. Studies were made of the effects of two white-rot fungi ( Polyporus versicolor and Stereum frustulatum) on the lignin model compounds guaiacylglycerol-β-guaiacyl ether and veratrylglycerol-β-guaiacyl ether. Only the guaiacyl model contains a phenolic hydroxyl group, but both compounds contain a β-alkyl-aryl ether linkage— the most common intermonomer bond in lignin. 2. 2. In cultures grown on a synthetic liquid both fungi converted the guaiacyl model to a number of products, prominent among which was the o, o′-dihydroxybiphenyl dehydrodimer. This biphenyl derivative was also a dominant product when this same model was incubated with a p-diphenol oxidase ( p-diphenol:O 2 oxidoreductase, EC 1.10.3.2, formerly known as laccase) purified from cultures of P. versicolor. 3. 3. The veratryl compound was not affected under the above cultural conditions or by the purified oxidase but was oxidized by both organism in a wood-meal medium. The only product observed was identified as α-guaiacoxy-β-hydroxypropioveratrone. Veratrylglycerol-β-guaiacyl ether was oxidized to the veratrone also by (i) the 2,4,6-triphenylphenoxyl radical in benzene and (ii) the above purified p-diphenol oxidase in the presence of spruce milled wood lignin. Thus, it is likely that its oxidation by the fungi in wood-meal cultures was via free radicals, with the lignin in the wood serving as a substrate for radical formation by phenol oxidases of the fungi. 4. 4. These results are interpreted to indicate that a postulated phenol oxidase hypothesis for lignin depolymerization provides a more promising basis than does a “β-etherase” hypothesis for further research with both P. versicolor and S. frustulatum. This interpretation is further supported by failure of the two fungi to affect dl-glycerol-β-guaiacyl ether in a synthetic liquid medium.