Metabolism of L-phenylalanine in the lignin-degrading white-rot fungi Bjerkandera adusta and Ischnoderma benzoinum

Two white-rot lignin degrading fungi Bjerkandera adusta and Ischnoderma benzoinum were cultivated on a liquid medium supplemented with L-phenylalanine, a precursor for benzaldehyde (bitter almond aroma) and benzyl alcohol. Remarkable amounts of benzaldehyde (587 mg/l) were only found in immobilized ton polyurethane foam cubes) cell cultures of Bjerkandera adusta. Benzyl alcohol was produced by both strains (340 mg/l). An extracellular aryl-alcohol oxidase (AAO) activity was only detected in the fungus Bjerkandera adusta. Previously published results show that AAO activity was significantly enhanced in immobilized cells cultures, suggesting that it could play an important role in benzaldehyde biosynthesis (Lapadatescu et al. 1997). Aryl metabolites produced were identified for both strains by GC-MS analyses. Tracer studies experiments using C-14- and C-13- labelled L-phenylalanine were employed with B. adusta. A metabolic pathway for B. adusta was proposed.