Selection and improvement of lignin-degrading microorganisms: potential strategy based on lignin model-amino Acid adducts.

The purpose of this investigation was to test a potential strategy for the ligninase-dependent selection of lignin-degrading microorganisms. The strategy involves covalently bonding amino acids to lignin model compounds in such a way that ligninase-catalyzed cleavage of the models releases the amino acids for growth nitrogen. Here we describe the synthesis of glycine-N-2-(3,4-dimethoxyphenyl)ethane-2-ol (I) and demonstrate that growth (as measured by mycelial nitrogen content) of the known lignin-degrading basidiomycete Phanerochaete chrysosporium Burds. with compound I as the nitrogen source depends on its production of ligninase. Ligninase is shown to catalyze the oxidative C-C cleavage of compound I, releasing glycine, formaldehyde, and veratraldehyde at a 1:1:1 stoichiometry. P. chrysosporium utilizes compound I as a nitrogen source, but only after the cultures enter secondary metabolism (day 3 of growth), at which time the ligninase and the other components of the ligninolytic system (lignin --> CO(2)) are expressed. Compound I and related adducts have potential not only in the isolation of lignin-degrading microbes but, perhaps of equal importance, in strain improvement.