Biodegradation of cinnamates by white-rot fungus, Phlebia radiata

Abstract

This study was attempted to elucidate the biochemical mechanism of cinnamate compounds labeled specifically 14C in the different position. The pathways for cinnamate metabolism have been studied in detail for the white-rot fungus Phlebia radiate and the reaction sequence has been proposed. 14CO2 release from carboxyl labeled cinnamate reached the maximum after 24 hrs on the medium with wheat straw and after 48 hrs on the media with glucose and spruce wood. In the case of the medium with cellulose the release of carbon dioxide increases linearility up to the 8 th day of the cultivation. The evolution of carbon dioxide from aliphatic chain cleavage cinnamate showed very similar trend which demonstrated simultaneous process with the decarboxylation ones on all tested media. About 30% of carbon dioxide evolved from carboxyl-labeled cinnamate. The radioactivity in the mycelium was also above 10% in all cases and can be read as partially degraded or metabolized to the other components. The cellulose slightly repressed the decarboxylation of cinnamate in opposition to wheat straw and spruce wood, which doubled degradation. The maximum rate of decarboxylation was ca. 1.2% of the applied activity evolved as 14CO2 per hour. According to identified metabolites, at first the substrates after decarboxylation, and aliphatic chain cleavage were demethylated in the position 4 following the demethylation in the position 3 and finally aromatic ring cleavage were observed in air and oxygen aeration on the media with glucose, cellulose, wheat straw and spruce wood.