Cleavage of β,β-carotene to flavor compounds by fungi

Abstract

More than 50 filamentous fungi and yeasts, known for de novo synthesis or biotransformation of mono-, sesqui-, tri-, or tetraterpenes, were screened for their ability to cleave β,β-carotene to flavor compounds. Ten strains discolored a β,β-carotene-containing growth agar, indicating efficient degradation of β,β-carotene. Dihydroactinidiolide was formed as the sole conversion product of β,β-carotene in submerged cultures of Ganoderma applanatum, Hypomyces odoratus, Kuehneromyces mutabilis, and Trametes suaveolens. When mycelium-free culture supernatants from five species were applied for the conversions, nearly complete degradation of β,β-carotene was observed after 12 h. Carotenoid-derived volatile products were detected in the media of Ischnoderma benzoinum, Marasmius scorodonius, and Trametes versicolor. β-Ionone proved to be the main metabolite in each case, whereas β-cyclocitral, dihydroactinidiolide, and 2-hydroxy-2,6,6-trimethylcyclohexanone were formed in minor quantities. Using a photometric bleaching test, the β,β-carotene cleaving enzyme activities of M. scorodonius were partially characterized.