Nootkatone.

The continuing interest in the sesquiterpene ketone (+)-nootkatone is stimulated by its strong grapefruit-like odor and numerous further bioactivities. Also numerous were the attempts to chemosynthesize or biotechnologically produce the compound. Cytochrome P450 enzymes from bacteria and fungi were intensively studied and expressed in Escherichia coli and in more food compatible hosts, such as Saccharomyces cerevisiae. The lipoxygenase-catalyzed generation was demonstrated using an enzyme from several Pleurotus species. Laccases required artificial mediators for an efficient catalysis. More recently, plant valencene synthases were expressed in microbial hosts. Combined with an endogenous farnesyl diphosphate delivery pathway and a valencene oxidase, this approach opened access to high yields of nootkatone possessing the appreciated attribute of "natural" according to present food legislation. Little biochemical engineering was carried out on the novel recombinant strains, leaving many options for future improved bioprocesses.