Degradation of benzyl ether bonds of lignin by ruminal microbes

We examined microbial activity in the rumen to cleave benzyl ether bonds of lignin model compounds that fluoresced when the bonds were cleaved. 4-Meth ylumbelliferone veratryl ether dimer was degraded completely within 8 h eve n in the presence of fungicidal antibiotics. but no significant degradation occurred with bactericidal antibiotics. Degradation of a phenolic beta-O-4 trimer incorporating 4-methylumbelliferone by a benzyl ether linkage was s timulated by ruminal microbes, although its corresponding non-phenolic mode l compound, 1-(4-ethoxy-3-methoxyphenyl)-1-O-(4-methylumbelliferyl)-2-(2-me thoxyphenoxy)-3-propanol, was not degraded. A coniferyl dehydrogenation pol ymer bearing fluorescent beta-O-4 benzyl ether that contains both phenolic and non-phenolic benzyl ether bonds was partially degraded (about 20%) in 4 8 h. These results suggest that ruminal microbes decompose benzyl ether lin kages of lignin polymers under anaerobic conditions. (C) 2000 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.