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

Abstract

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.