Biosynthesis of carotenoids in Brevibacterium sp. KY-4313.

The biosynthesis of 4-keto and 4,4'-diketo carotenoids in Brevibacterium sp. KY-4313 was studied. Echinenone and canthaxanthin were isolated from the cultures grown on a medium containing several n-alkanes. When glutathione was added to the bacterial cultures, the formation of canthaxanthin was inhibited while beta-carotene and its hydroxy derivatives accumulated. It is suggested that these 4-hydroxy compounds, isocryptoxanthin, isozeaxanthin, and 4-hydroxy-4'-keto-beta-carotene, are intermediates in the biosynthesis of canthaxanthin. In the presence of 2-(4-chlorophenylthio)-triethylamine hydrochloride or nicotine, lycopene and neurosporene accumulated. The beta-carotene level decreased slightly but beta-zeacarotene remained unchanged. beta-carotene and its derivatives were resynthesized upon removal of the inhibitors. It was concluded that cyclization can take place at either the neurosporene or lycopene level in Brevibacterium sp. KY-4313.