Background. Carotenoids are a diverse group of pigmented isoprenoid compounds. They are now commercially extracted mainly from plants or by a chemical synthesis, from which 80-90 % of compounds are obtained. However, synthetic carotenoids, if provided in huge amounts, can be harmful to human health, whereas waste generated in their production process poses an environmental risk. An alternative to the equivalent of a chemical synthesis is to use microbial production to obtain carotenoids with a high biological activity, which could be a natural and functional additive in various industries. Therefore, the aim of the study was to optimize the culture conditions and biosynthesis of selected carotenoid fractions by Rhodotorula strains. Yeast culture was developed in 100 cm³ flasks in which 50 cm³ of YPG medium was prepared with constant shaking and access to light. The regulation of carotenoid biosynthesis took into account the influence of the following factors: temperature, pH and a carbon/nitrogen ratio. A spectrophotometric method was used to determine the fraction of carotenoids in terms of quantity and quality.
Results and conclusions. The effects of temperature, C/N ratio and pH on the amount of biomass obtained were demonstrated. Changing pH conditions determined significant differences in the determined carotenoid fractions regardless of a strain. Moreover, the application of extreme pH values did not inhibit the growth or synthesis of carotenoids, pointing to the adaptation of Rhodotorula sp. to stressful environmental conditions. A variable increase in biomass of the strains tested was found depending on the culture conditions, which affected the logarithmic growth curve of the yeast. An analysis of the influence of physicochemical factors allowed for the identification of culture conditions favorable for carotenoid production.