Nechai G. Selection, physiological and biochemical characterisation of the yeast Xanthophyllomyces dendrorhous, enriched by selenium and able to produce chromium(ІІІ) biocomplexes

Object of the research: carotenogenesis in the X. dendrorhous yeasts and reduction processes of selenite and chromate, impact of selenium containing biomass of carotene synthesizing yeasts on the antioxidant status of rats intoxicated by tetrachloromethane (TCM). Aim of the work: to obtain mutants of carotene synthesizing yeast X. dendrorhous with modified sensitivity/ resistance to selenium and chromium oxianions and to characterize their physiological and biochemical properties, determine the basic regularities in selenite and chromate detoxification in the selected strains, ascertain the effect of these yeast preparations as a source of carotenoids and biologically active forms of Se and Cr on the processes of lipid peroxidation and antioxidant status of tissues in the liver and blood of rats under conditions of oxidative stress induced by the injection of TCM. Methods: biochemical, physical - chemical, microbiological, statistical. For the first time was obtained a collection of strains of selenite-resistant, carotene synthesizing yeast X.dendrorhous with modified sensitivity/ resistance to compounds of selenium and chromium. Investigated reduction mechanism in providing selected mutants with resistance to selenite and chromate. It was determined that sodium selenite and potassium chromate inhibit the growth and carotenogenesis of yeast X. dendrorhous cells and initiate oxidative stress. These yeasts are able to detoxify selenium and chromium oxianions through their recovery, as a result, besides organic forms of Selenium, nanoscale particles of elemental Selenium are formed and Cr(III) biocomplexes are accumulated in the culture liquid, respectively. It was found that addition of selenium-enriched biomass of the yeast X. dendrorhous to the diet of the intoxicated by TCM rats inhibits development of oxidative stress, reduces level of products of proteins oxidative modification and lipid peroxidation, and activates antioxidant enzymes. Corrective effect of selenium-enriched biomass of the yeast X. dendrorhous on development of oxidative stress is more effective in comparison with not selenizaid cells or sodium selenite. Selected mutant strains of yeast X. dendrorhous are of practical interest for biotechnological obtaining of biomass enriched with astaxanthin and biological forms of selenium and Cr(III), which in the future can be used as a valuable feed or food additive. Fields of application: biochemistry, biotechnology, microbiology.