Toxicological assessment of the yeast Rhodotorula gracilis in experimental animals

 Rhodotorula gracilis is an oleaginous yeast known to synthesize lipids and carotenoid pigments. In this study, the toxicological evaluation of a locally isolated strain, R. gracilis CFR-1, in freeze-dried form has been studied to assess its safety as a source of natural colorant and nutritional additive in experimental animals. Acute and subacute studies on freeze-dried R. gracilis were conducted on both sexes of albino rats. Acute doses of R. gracilis at 0.5–6.0 g/kg body weight (w/w) did not show any symptoms of toxicity nor mortality of the adult rats. Feeding of low concentrations of R. gracilis at the 0.1–2.0% level (w/w) for 14 weeks did not induce any significant change in food intake and gain in body weight of the experimental rats compared to control animals. There were no significant differences in the absolute and relative weights of vital organs, hematological parameters, macroscopic and microscopic changes in vital organs and serum enzyme levels between the experimental and control groups. The fecal matter of R. gracilis-fed rats did not show any viable cells. The results clearly show that acute and subacute oral feeding of freeze-dried whole cells of R. gracilis for 14 weeks did not produce any toxic effects on male and female rats.