Reduction of chromate and carotene-synthesizing activity of selenite-resistant mutants of the yeast: Xanthophyllomyces dendrorhous (Phaffia rhodozyma)

Abstract

Aim. The yeast P. rhodozyma is a perspective microbial producer of carotenoid pigment astaxanthin with a high antioxidant power. The aim of the work was to study the ability of the selenite-resistant strains of this yeast to reduce chrome(VI) compounds, as well as to analyze the relations between synthesis of carotenoids, resistance to selenite and chromate-reducing activity of P. rhodozyma. Methods. The yeast cells were grown at standard conditions for this species. The residual chromate content in cultural liquid was determined colorimetrically using diphenylcarbazide. The carotenoid content was determined after extraction of the pigments from the previously permeabilized cells by organic solvents. Results. The selected selenite-resistant mutants of the yeast P. rhodozyma revealed the different combinations of the phenotypes related with tolerance/sensitivity to chromate and selenite, as well as ability to reduce chromate. Conclusions. The obtained results give reasons for suggesting that pathways of detoxification of chromate and selenite by the yeast P. rhodozyma are different, although run through a common reductive type. The isolated mutant strains would be served as the useful models to study relations between homeostasis of Se and Cr oxyanions and biosynthesis of carotenes.