Biotransformation of Citral by Botrytis cinerea

Abstract

Biotransformation of citral (1) was studied with four strains of Botrytis cinerea using grape must (A), a synthetic medium (B) and mixtures of A and B. Whereas in A complete metabolization of 1 without evidence of any volatile product was observed, in B nerol (2) and geraniol (3) were found as predominant volatile bioconversion products; in minor amounts (E,Z)-2,6-dimethylocta- 2,6-dien-1,8-diol (4) and (E,E)-2,6-dimethylocta-2,6-dien-1,8-diol (5). 2-methyl-2-hepten-6-one (6), 2-methyl-2-hepten-6-ol (7), 2-methyl-2-hepten-6-one-1-ol (8) and 2-methyl-y-butyrolactone (9) were identified. Using small amounts of A in B (1:700 to 5:700) low yields of 2 and 3 were obtained, whereas the quantities of 4, 5. 6 and 8 increased. Quantitatively, the results were strongly dependent on the strains used. The bioconversion products were all identified by capil­lary gas chromatography (HRGC) and coupled HRGC techniques, i.e. -mass spectrometry (HRGC-MS) and -Fourier transform infrared spectroscopy (HRGC-FTIR).