Influence of nicotine and diphenylamine on the carotenoid composition of Rhodotorula strains

Abstract

In order to obtain commercially interesting carotenoid profiles, the effect of supplementation with diphenylamine (DPA) and nicotine in the culture media of Rhodotorula rubra and Rhodotorula glutinis was studied. Fermentation experiments were carried out in flasks. The carotenoids were extracted with ethyl acetate by physical disruption, and analyzed by high-performance liquid chromatography using a reversed-phase column. At subinhibitory levels, both the inhibitors showed no effect on yeast growth for the two strains. Only R. rubra produced more carotenoids when 5 mu mol of DPA was added to the broth, 155.8 mu g/g of dry weight. For both strains, supplementation with 5 mu mol DPA caused a significant reduction in the torularhodin/torulene ratio, from 1.5 to 0.5 for R. rubra, and from 0.8 to 0.5 for R. glutinis. With 10 mu mol of this inhibitor, an accumulation of beta-carotene occurred from 13 to 47% in R. rubra, and from 36 to 43% in R. glutinis. Supplementation with nicotine resulted in the selective biosynthesis of lycopene (up to 93.8 mu g/g) and the formation of a minor carotenoid, tentatively identified as 3,4-didehydrolycopene, not previously related to Rhodotorula spp.