Diastereomer selectivity in the degradation of a lignin model compound of the arylglycerol β-aryl ether type by white-rot fungi

Mixtures of about equal amounts of the diastereomers of arylglycerol β-aryl ether 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol (1) were added to cultures of Trametes versicolor, Phanerochaete chrysosporium, and Pycnoporus cinnabarinus. Samples taken from the fungal cultures were analyzed with respect to the fraction of 1 degraded, the erythro:threo ratio in the remaining 1, and the product profile, using HPLC and UV-diode array detector. The P. cinnabarinus cultures exhibited laccase activity and partially decolorized Remazol Brilliant Blue R (RBBR), but they did not degrade 1 under the conditions studied. Cultures of T. versicolor and P. chrysosporium preferentially degraded the threo isomer of 1. This is consistent with the fact that the product profiles showed larger amounts of threo- than erythro-veratrylglycerol. The results can be discussed in relation to the diastereomer selectivity of various oxidants implicated in lignin degradation by white-rot fungi. Preferential degradation of the threo isomer of arylglycerol β-aryl ethers is not in agreement with the action of Fentonʹs reagent, since this reagent does not exhibit any stereopreference.