Assessing the effect of engineered nanoparticles on microalgae Tetradesmus obliquus, for enhanced biomass production and CO₂ sequestration

This study engineered a series of novel nickel-doped ceria nanoparticles to assess their supplementation effects on the microalgae Tetradesmus. Nanoparticles (NPs) were synthesized using the co-precipitation method and characterized by various techniques. The synthesized NPs were utilized to assess the effects of different dosages on the physiology (F_v/F_m), chlorophyll-a content, and biochemical composition of T. obliquus growth. Different dosages (5, 10, 20, and 50 mg/L) of 0 %Ni@CeO₂, 0.25 %Ni@CeO₂ and 0.5 %Ni@CeO₂ NPs were added in BG11 for investigation. Results show that 0.25 %Ni@CeO₂ (20 mg/L) NPs show the highest (2.19 g/L) biomass production compared to BG11 (1.67 g/L), and other NPs added media. Similarly, the protein content in 0.25 %Ni@CeO₂ (20 mg/L) medium was ~14 % and 29.74 % higher compared to BG11 and 0 %Ni@CeO₂ (5 mg/L) medium. The lipid and carbohydrate content in NPs-supplemented growth media shows a higher yield than BG11. The maximum higher (22.06 MJ/kg) heating value (HHV) was observed in 0.25 %Ni@CeO₂ (20 mg/L), followed by 20.67 MJ/kg in 0 %Ni@CeO₂ (20 mg/L). Similarly, the highest CO₂ fixation rate (0.28 gCO₂/L/d) was observed in 0.25 %Ni@CeO₂ (20 mg/L). This research shows that 0.25 %Ni@CeO₂ (20 mg/L) addition in BG11 medium is a promising strategy to enhance microalgae growth, biochemical content, and CO₂ sequestration. Furthermore, this study provides a detailed insight into the interaction mechanism between 0.25 %Ni@CeO₂ NPs and the microalgal photosystem. The finding might be easily scaled up at the demonstration scale for enhanced biomass production.