High-value lipids accumulation by Pavlova pinguis as a response to nitrogen-induced changes

The challenges of exploring the potential of microalgal strains for biotechnological applications include the optimization of their cell growth and chemical composition. To overcome this, it is essential to understand the mechanisms that lead to the accumulation of desired products within microalgal cells. In this study, a gradient of nitrogen as nitrate (NO3–N) concentrations was used for the preparation of P. pinguis growth medium. The algal growth dynamics, pigments, nutrient uptake, and detailed lipid composition across treatments were assessed. Increasing the NO3–N level led to higher lipid content (21%), a higher cell uptake rate (0.20 pg NO3–N cell-1 d-1) and more accumulation of chlorophylls, carotenoids, and high-value lipids. Eicosapentaenoic acid, essential fatty acids, phytol and stigmasterol were the key high-value lipids that were positively influenced by higher NO3–N levels. High NO3–N conditions induced an increase of 54% in total sterol content, while low NO3–N conditions resulted in increased proportions of saturated fatty acids (66% more) and decreased proportions of polyunsaturated fatty acids (14% less). The low NO3–N level also led to higher amounts of monoglyceride (1.60 mg g-1; 64% more). The analysis of P. pinguis lipids before and after hydrolysis provided an insight into the composition of the esterified lipids across treatments. NO3–N supplementation was revealed to be an effective strategy for enhancing P. pinguis lipid composition, for nutraceutical and pharmaceutical industries (high NO3–N level). A greater understanding of the NO3–N uptake and the use efficiency by P. pinguis was reached, showing its potential for further biotechnological applications.