Glucose exerts a negative effect over a peroxidase from Trichosporon asahii, with carotenoid cleaving activity.

Tobacco aroma compounds were generated via lutein cleavage by the combined action of a yeast and a bacterium identified as Trichosporon asahii and Paenibacillus amylolyticus, respectively. In this study, an inverse relationship between glucose concentration and the generation of three compounds, present in the tobacco aroma profile, was observed in mixed cultures. In order to identify the organism sensitive to the sugar effect, both were grown separately. The presence of glucose suppressed beta-ionone production by T. asahii grown with lutein. However, the biotransformation of the ionone into its reduced derivatives (7,8-dihydro-beta-ionone and 7,8-dihydro-beta-ionol) by P. amylolyticus was not affected by the sugar. This pointed to the cleavage of lutein, a step within the process necessary for the synthesis of beta-ionone, as the target of the glucose effect. In vitro studies with crude extracts and concentrated cell-free medium derived from T. asahii cultures showed that the carotenoid breakdown activity was located extracellularly and only detected in supernatants from yeast cells grown in the absence of the sugar. Rather than an inhibition or a mechanism affecting the enzyme secretion, the glucose effect on lutein degradation comprised another regulatory level. Further experiments showed that the enzyme responsible for lutein breakdown and susceptible to the sugar effect exhibited a high degree of identity to fungal peroxidases, studied as well, for their involvement in carotenoid cleavage.

Bioconversion of lutein using a microbial mixture--maximizing the production of tobacco aroma compounds by manipulation of culture medium.

The generation of aroma compounds by carotenoid cleavage in the 9-10 position was studied, due to the importance of these compounds in the flavor and fragrance industry. The bioconversion of the carotenoid lutein to C(13) norisoprenoids utilizing a microbial mixture composed of Trichosporon asahii and Paenibacillus amylolyticus was carried out by a fermentation process. Applying an experimental design methodology, the effects of nutritional factors on the production of aroma compounds present in the tobacco profile were studied. After an assessment of the significance of each nutritional factor, the levels of the variables yielding the maximum response were calculated. Glucose, tryptone, and yeast extract exerted a strong negative effect over the objective function, with glucose being the strongest. Lutein possessed a positive effect over the tobacco aroma production, while sodium chloride and trace elements showed no influence over the process. The yield attained after culture medium manipulation was almost ten-fold higher, compared with the base medium; and the aroma mixture was characterized as: 7,8-dihydro-beta-ionol (95.2%), 7,8-dihydro-beta-ionone (3.7%), and beta-ionone (1.1%).