Hydroxylation of biphenyl by the yeast Trichosporon mucoides

Hydroxylation of biphenyl by the dibenzofuran-degrading yeast Trichosporon mucoides SBUG 801 was studied. Glucose-grown cells degraded 40% of the biph enyl added within the first 24 h of incubation. The first step in the biotr ansformation pathway was the mono-hydroxylation of the biaryl compound to p roduce 2-, 3-, and 4-hydroxybiphenyl. Further oxidation produced seven dihy droxylated intermediates; the second hydroxyl group was added either on the aromatic ring already hydroxylated or on the second ring. Of all metabolit es, 2,5-dihydroxybiphenyl accumulated in the supernatant in the highest con centration. The initial hydroxylation favors the 4-position to produce 4-hy droxybiphenyl, which is subsequently hydroxylated to form 3,4-dihydroxybiph enyl. When biphenyl was replaced as a substrate by 4-hydroxybiphenyl, furth er hydroxylation of the intermediate 3,4-dihydroxybiphenyl resulted in 3,4, 4'-trihydroxybiphenyl. Incubation of T. mucoides with biphenyl and O-18(2) indicated a monooxygenase-catalyzed reaction in the oxidation of biphenyl. The hydroxylation was inhibited by 1-aminobenzotriazole and metyrapone, kno wn cytochrome P450 inhibitors. These results are very similar to those obse rved in the biotransformation of biphenyl in mammals.