Nitrate and silicate limitations induce metabolic reprogramming and lipid redistribution in Navicula incerta, enhancing biodiesel properties

Nutrient limitations alter microalgae metabolism and fatty acid biosynthesis, modifying the lipid profile and improving the chemical properties of the resulting biodiesel. This study investigated the effects of nitrate and silicate limitations on the proteomic and lipid profiles in Navicula incerta and its biodiesel potential. Proteomic analysis revealed 287 differentially abundant proteins (DAPs) out of 558 identified, with silicate-limited conditions showing the highest number of DAPs (212) and nitrogen-limited conditions showing 125 DAPs (log2FC > |0.57|, p-value <0.05). These changes underpin two distinct survival strategies: nitrogen limitation forced a broad metabolic shutdown, while silicate limitation prompted a strategic reallocation of resources, maintaining core biosynthesis and enhancing internal recycling. Both stresses induced a convergent lipid remodeling characterized by decreases in saturated fatty acids and increases in monounsaturated and polyunsaturated fatty acids. This shift optimizes membrane fluidity for stress resistance and enhances key biodiesel properties, confirming the potential of N. incerta as a sustainable source of high-quality biodiesel. These findings highlight the diatom's metabolic flexibility in optimizing resource allocation for survival, a trait that can be harnessed to tailor lipid profiles for advanced biofuel applications. Future work should focus on the impact, efficiency, and economic feasibility of cultivating N. incerta under nutrient stress. SIGNIFICANCE: Understanding the relationship between nitrogen and silicate concentrations and protein accumulation is crucial for harnessing the potential of microalgae in various industries and addressing environmental challenges. The proteomic analysis and lipid profiles obtained in N. incerta under nitrogen and silicate limitation demonstrate remarkable metabolic flexibility in response to nutrient limitations, optimizing resource allocation to ensure survival under nutrient stress. Nitrogen limitation drives the accumulation of carbohydrates and dry biomass, along with lipid mobilization and a shift toward unsaturated fatty acids, enhancing energy efficiency and membrane functionality. Silicate limitation, while having a milder effect, prioritizes resource conservation and the redistribution of existing reserves. These adaptive responses highlight the diatom's ability to maintain critical cellular functions under adverse conditions and reveal its potential for biodiesel production.