Transcriptomic analyses reveal the upregulation of the fatty acids metabolism genes in Thalassiosira weissflogii during low optimal phosphate concentration

Fatty acids from microalgae like Thalassiosira weissflogii are valuable for various applications, including aquaculture feed . Maximising the percentage of fatty acids with total lipids relies on several cultivation variables, including the amount of phosphate in the culture media. While it's known that factors like phosphate levels can affect lipid and fatty acid production , the specific impact of low phosphate on T. weissflogii has not been well-studied. Thus, this study aims to determine how different low phosphate concentrations influence biomass, lipid content, and fatty acid production in T. weissflogii . In addition, this study also seeks to determine the potential molecular responses of T. weissflogii in optimum low phosphate concentrations. T. weissflogii were cultured in four different phosphate concentrations—0.064, 0.129, 0.193, and 0.258 μM, and accumulation of biomass, total lipids, and fatty acids were measured. A phosphate concentration of 0.064 μM was recorded to produce the highest biomass (27.47 g/L), total lipids (28.36 %), and eicosapentaenoic (EPA) fatty acid (6.83 mg/g). The transcriptome profiling under the optimal low phosphate concentration of 0.064 μM identified 40,212 differential expressed genes (DEGs), including FabG, FAD2 , HSD17B12, and FadD genes in the significant fatty acid metabolism pathways. These findings suggested that 0.064 μM phosphate concentrations should be used in T. weissflogii cultivation. Further work should be undertaken to determine how allelic variation in upregulated genes in combination with phosphate concentration affects biomass, total lipids, and high-value fatty acids in T. weissflogii . In addition, genetic improvement through genetic selection or gene editing experiments in T. weissflogii could be explored to optimise feeds to enhance the growth and health of aquaculture species, including finfish and shellfish. • Thalassiosira weissflogii was cultured as a live feed and fatty acid source in aquaculture. • 0.064 μM phosphate concentration accumulated the highest biomass, total lipids, and eicosapentaenoic acid (EPA). • Fatty acid metabolism was the most significant pathway in 0.064 μM phosphate cultivation. • FabG, FAD2 , HSD17B12, and FadD genes are up-regulated in fatty acid metabolism . • Recommended concentration for cultivation to maximise total lipids is 0.064 μM phosphate.