Microbial Transformation of beta-Ionone and beta-Methylionone

Aspergillus niger JTS 191 was selected from many microorganisms tested as capable of converting ionones to other compounds having aromas. The individual transformation products from beta-ionone were isolated and identified by comparison with synthetically derived compounds. The major products were (R)-4-hydroxy-beta-ionone and (S)-2-hydroxy-beta-ionone. 2-Oxo-, 4-oxo-, 3,4-dehydro-, 2,3-dehydro-4-oxo-, 3,4-dehydro-2-oxo-, (S)-2-acetoxy-, (R)-4-acetoxy-, and 5,6-epoxy-beta-ionone and 4-(2,3,6-trimethylphenyl)-but-3-en-2-one were also identified. Analogous transformation products of beta-methylionone also were identified. Based on gas-liquid chromatographic analysis during the fermentation, we propose two main oxidative pathways of beta-ionone. The results of this study suggest that these transformations of beta-ionones may be useful as tobacco-flavoring compounds.