Rhodotorula yeast species find application in a variety of fields, such as pharmaceutical, cosmetics, medicine, and food industry. They can provide economic and health benefits, as source of carotenoid pigments, proteins, and carbohydrates. To increase the productivity and biosynthesis of biologically active substances, the biotechnology uses nanoparticles that can act as precursors, stimulators or inhibitors of the synthesis. In this context, it is important to know the influence of nanoparticles on cellular structures and functions of living organisms. The main yeasts advantage is their rapid adaptability: they grow up easily and are high productive, when the culture medium and cultivation conditions are adjusted for the purpose of optimized biosynthesis. They are also resistant to alien microflora and do not pollute the environment. Thus, the study of the influence of metal nanoparticles on yeasts metabolism could facilitate their use in biotechnology. The effects of nanoparticles on yeast Rhodotorula gracilis CNMN-Y-30 was evaluated by determining the productivity and chemical composition of the biomass in response to supplementation of YPD medium with different concentrations (0.5; 1.0; 5.0; 10.0; 15.0 mg/L) of iron oxide nanoparticles with size of 10 and 30 nm. The nanoparticles were synthesized by the researchers of the Institute of Electronic Engineering and Nanotechnology of ASM. The productivity, protein and carbohydrate content in yeast biomass were evaluated after 120 hours of cultivation. The results of our study revealed that Fe3O4 nanoparticles did not initiate essential disturbances of yeast development. Changes of biomass productivity were established only at concentrations 0.5 and 1.0 mg / L of Fe3O4 nanoparticles with a size of 10 nm, which increases the accumulation of cell biomass with 13.3% -14.8%. The protein content in yeast biomass increased with 14.1% – 23.8% during the growth on the medium supplemented with Fe3O4 (30 nm). The use of Fe3O4 nanoparticles with a size of 10 nm had another effect: using the concentration of 15 mg / L of nanoparticles we noticed a decrease of the protein content with 28.8% compared to the control sample. The response reaction of yeast Rhodotorula gracilis CNMN-Y-30 was manifested by favorable changes in the carbohydrate content (increase by 13%- 21.3% compared to the control sample) in the presence of nanoparticles with size of 30 nm. In the experimental variants using Fe3O4 nanoparticles with a size of 10 nm, the results indicate lower values for carbohydrate content. In conclusion, we can affirm that the productivity and the biosynthesis of proteins and carbohydrates in the biomass of Rhodotorula gracilis CNMN-Y-30 is influenced by the size and concentration of Fe3O4 nanoparticles added to the growth medium.