Effect of exogenous stress factors on the biosynthesis of carotenoids and lipids by Rhodotorula yeast strains in media containing agro-industrial waste.

In this study, we aimed to determine the effect of exogenous stress factors (sodium chloride as osmotic stressor, hydrogen peroxide as an inducer of oxidative stress, white light irradiation, and low temperature) on the biosynthesis of carotenoids and lipids by red yeast (Rhodotorula glutinis, R. mucilaginosa, and R. gracilis) during cultivation in media containing potato wastewater and glycerol. According to our results, the yeast were able to grow and biosynthesize lipids and carotenoids in the presence of the applied stress factors. Low temperature caused an increase in the biosynthesis of intracellular lipids and carotenoids. R. gracilis synthesized lipids (21.1 g/100 g) and carotenoids (360.4 µg/g) in greater quantities than that of other strains. Under these conditions, there was also an increase in the content of unsaturated fatty acids, especially linoleic and linolenic acids. The highest percentage of polyunsaturated fatty acid (PUFA) (30.4%) was synthesized by the R. gracilis yeast after cultivation at 20°C. Their quantity was 2.5-fold greater than that of the biomass grown in control conditions. The contribution of individual carotenoid fractions depended both on the yeast strain and the culture conditions. Induction of osmotic stress and low temperature intensified the biosynthesis of β-carotene (up to 73.9% of the total carotenoid content). In oxidative stress conditions, yeast synthesized torulene (up to 82.2%) more efficiently than under other conditions, whereas white light irradiation increased the production of torularhodin (up to 20.0%).