Light and Temperature Effects on the Accumulation of Carotenoids in <i>Rhodotorula</i> spp. Yeasts

Carotenoids are widely recognized for their antioxidant and health-beneficial properties, making them attractive for applications in the food, pharmaceutical, medical, and agricultural sectors. <i>Rhodotorula</i> yeasts are considered one of the most suitable alternatives for carotenoid synthesis due to their rapid biomass growth and high pigment yield. During this study, based on the sequences of the ITS region between 18S and 28S rRNA genes, the yeast strains were identified as belonging to <i>Rhodotorula babjevae</i>, <i>R. dairenensis</i>, <i>R. diobovata</i>, <i>R. glutinis</i>, <i>R. graminis</i>, <i>R. ingeniosa</i>, <i>R. kratochvilovae</i>, and <i>R. mucilaginosa</i>. The production of carotenoids by different <i>Rhodotorula</i> yeast strains was analyzed under the combined effects of lighting and temperature. Among all tested strains, the isolate identified as <i>R. ingeniosa</i> exhibited the lowest carotenoid content, ranging from 0.18 to 0.23 mg/g biomass. The highest levels of pigment were accumulated in dark conditions by <i>R. babjevae</i> (0.86 mg/g biomass) and <i>R. graminis</i> (0.76 mg/g biomass) cultivated for 14 days at a constant temperature of 26 °C, and by <i>R. glutinis</i> (0.89 mg/g biomass) after incubation at 4 °C. The majority of yeasts tested produced more carotenoids at a higher temperature. It was observed that in <i>R. babjevae</i>, <i>R. glutinis</i>, and <i>R. graminis</i>, lighting negatively affected the pigment content regardless of incubation temperature. In these strains, the pigment content decreased by 1.2- to 1.4-fold after one week of cultivation under light conditions at 26 °C, compared to cultures grown in the dark. The results suggest that the isolated <i>Rhodotorula</i> strains could be attractive candidates for the efficient synthesis of carotenoids.