Formation of coumarines during the degradation of alkyl substituted aromatic oil components by the yeast Trichosporon asahii.

In this study, we investigated the ability of the yeast Trichosporon asahii SBUG-Y 833 to assimilate phenylalkanes with alkyl chain lengths from 7 to 12 carbon atoms, and we describe for the first time the formation of coumarines via a novel degradation pathway other than the normal terminal and ss-oxidation pathway of the alkyl residues. Besides benzoic acid and its further oxidation products, six new metabolites were identified. These were the three coumarines--4-hydroxycoumarin, 4,6-dihydroxycoumarin, 4,8-dihydroxycoumarin-and the three alkyl substituted aromatic acids--7-phenylheptanoic acid, 2-hydroxyphenylheptanoic acid, and 2-hydroxyphenylpropanoic acid. 4-Hydroxycoumarin was the main extracellular metabolite during the degradation of both odd- and even-chain phenylalkanes and was also produced during further biotransformation of 2-hydroxyphenylpropanoic acid and trans-2-hydroxycinnamic acid. Due to the ability of T. asahii to form hydroxylated coumarines, the transformation of 7-hydroxycoumarin and 2,4-dihydroxyphenylpropanoic acid was investigated. Yeast cells supplemented with 7-hydroxycoumarin formed 6,7-dihydroxycoumarin and 4,7-dihydroxycoumarin. The transformation of 2,4-dihydroxyphenylpropanoic acid yielded to 4,7-dihydroxycoumarin as the main product. All hydroxylated coumarines were continuously accumulated and are very resistant to further oxidation. The high potential of the yeast T. asahii SBUG-Y 833 to form different hydroxylated coumarines from alkylaromatics suggests possible applications in the biotechnological production of coumarine structures with medical potential as anticoagulative and antitumor pharmaceutical.