###### Abstract  
Microbial lipids called a sustainable alternative to traditional vegetable oils invariably capture the attention of researchers. In this study, the effect of limiting inorganic phosphorus (KH\({}_{2}\)PO\({}_{4}\)) and nitrogen ((NH\({}_{4}\))\({}_{2}\)SO\({}_{4}\)) sources in lipid-rich culture medium on the efficiency of cellular lipid biosynthesis by _Y. lipolytica_ yeast has been investigated. In batch cultures, the carbon source was rapesed waste post-frying oil (50 g/dm\({}^{3}\)). A significant relationship between the concentration of KH\({}_{2}\)PO\({}_{4}\) and the amount of lipids accumulated has been revealed. In the shake-flask cultures, storage lipid yield was correlated with lower doses of phosphorus source in the medium. In bioreactor culture in mineral medium with (g/dm\({}^{3}\)) 3.0 KH\({}_{2}\)PO\({}_{4}\) and 3.0 (NH\({}_{4}\))\({}_{2}\)SO\({}_{4}\), the cellular lipid yield was 47.5% (_w/w_). Simultaneous limitation of both phosphorus and nitrogen sources promoted lipid accumulation in cells, but at the same time created unfavorable conditions for biomass growth (0.78 g\({}_{\text{d.m.}}\)/dm\({}^{3}\)). Increased phosphorus availability with limited cellular access to nitrogen resulted in higher biomass yields (7.45 g\({}_{\text{d.m. }}\)/dm\({}^{3}\)) than phosphorus limitation in a nitrogen-rich medium (4.56 g\({}_{\text{d.m. }}\)/dm\({}^{3}\)), with comparable lipid yields (30% and 32%). Regardless of the medium composition, the yeast preferentially accumulated oleic and linoleic acids as well as linoleic acid up to 8.89%. Further, it is crucial to determine the correlation between N/P molar ratios, biomass growth and efficient lipid accumulation. In particular, considering the contribution of phosphorus as a component of coenzymes in many metabolic pathways, including lipid biosynthesis and respiration processes, its importance as a factor in the cultivation of the oleaginous microorganisms was highlighted. Yarmovia lipolytica; microbial lipids; phosphorus limitation; nitrogen limitation Article Phosphorus and Nitrogen Limitation as a Part of the Strategy to Stimulate Microbial Lipid Biosynthesis  
[PERSON], [PERSON], [PERSON]; [PERSON]; [PERSON], [PERSON]; [PERSON], [PERSON], [PERSON]. Nowadays, PUFA-rich SCOs are mainly extracted from microalgae due to the innate ability to synthesize valuable fatty acids and lipid production efficiency, such as _Schizochytrium_ sp. 50-77% of dry weight, _Nitzschia_ sp. 45-47%, _Nannochloropsis_ sp. 31-68% or _Neochloris oleoabundans_ 35-54% oil content [9]. Oleaginous yeasts, compared to microalgae, have a rather lower ability to synthesize SCO. Remarkably, wild yeast strains of _Y. lipolytica_ metabolizing glucose are able to store lipids up to 36% of cell dry weight, and even up to 50-60% in the case of feeding biomass with hydrophobic substrates [6; 10]. In SCO production, lipid yield per unit dry weight is a critical factor; thus, solutions are still being sought to improve it [11]. Fields such as synthetic and system biology, along with metabolic engineering techniques, are used to improve lipid storage yield and obtain lipids rich in polyunsaturated fatty acids (PUFAs). By using various molecular biology methods, it has been possible to obtain _Y. lipolytica_ yeast mutants capable of accumulating up to 25% eicosapentenoic acid in the total content of the fatty acids [12]. Oleaginous yeasts, depending on the type of carbon substrate in the culture medium, accumulate lipids through two different biochemical pathways: de novo for hydrophilic and ex novo for hydrophobic substrates. In recent years, research has been conducted to define and analyze genes associated with the activity of enzymes specific to both biosynthetic pathways [2; 13]. There are reports that sometimes cellular lipid accumulation may occur through two pathways simultaneously [2]. The yeast _Y. lipolytica_ is well known for its ability to metabolize complex lipid substrates, including industrial waste products [14].