Influence of cell immobilization on the production of benzaldehyde and benzyl alcohol by the white-rot fungi Bjerkandera adusta, Ischnoderma benzoinum and Dichomitus squalens

Abstract

Three white-rot basidiomycetes, Bjerkandera adusta, Ischnoderma benzoinum and Dichomitus squalens, 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⁻¹) were found in cultures of B. adusta. Immobilization of this fungus on polyurethane foam cubes allowed an 8.3-fold increase of the production of benzaldehyde and a 15-fold increase of the productivity as compared with non-immobilized cells. Aryl-alcohol oxidase activity was only detected in B. adusta. This activity was also significantly enhanced in immobilized cells, suggesting that it plays an important role in benzaldehyde biosynthesis. Conversely, consistent amounts of benzyl alcohol (340 mg l⁻¹ for B. adusta and I. benzoinum and 100 mg l⁻¹ for D. squalens) were produced by the three fungi when immobilized. Laccase activity was found only in the strains I. benzoinum and D. squalens. This activity was markedly enhanced in free cells cultures. Immobilization of the fungi did not promote benzyl alcohol production by comparison with free cell cultures (500 mg l⁻¹).