Phosphorus and Nitrogen Limitation as a Part of the Strategy to Stimulate Microbial Lipid Biosynthesis

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 (KH2PO4) and nitrogen ((NH4)(2)SO4) 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 rapeseed waste post-frying oil (50 g/dm(3)). A significant relationship between the concentration of KH2PO4 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 KH2PO4 and 3.0 (NH4)(2)SO4, 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(d.m.)/dm(3)). Increased phosphorus availability with limited cellular access to nitrogen resulted in higher biomass yields (7.45 g(d.m.)/dm(3)) than phosphorus limitation in a nitrogen-rich medium (4.56 g(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 linolenic 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.

Automated summary

Microbial lipids are considered a sustainable alternative to traditional vegetable oils and have gained attention among researchers. This study investigated the impact of limiting inorganic phosphorus and nitrogen sources on cellular lipid biosynthesis in Y. lipolytica yeast, revealing a significant relationship between phosphorus concentration and lipid accumulation. Simultaneously limiting both phosphorus and nitrogen sources promoted lipid accumulation but hindered biomass growth, highlighting the importance of phosphorus as a factor in cultivating oleaginous microorganisms.