Influence of nitrogen sources on growth and biochemical composition of Chlorella sorokiniana

The increasing demand for sustainable bioenergy solutions emphasizes the need of optimizing microalgae cultivation systems to achieve cost-effective and efficient biomass production. The potential of microalgae as a bioenergy feedstock is significantly influenced by nutrient optimization, particularly with respect to nitrogen. This study evaluated the effects of six nitrogen sources, each providing 25 mg N L⁻¹: sodium nitrate (SN), potassium nitrate (PN), ammonium acetate (AA), ammonium nitrate (AN), ammonium sulphate (AS), and urea (U) on growth of Chlorella sorokiniana growth, carbon dioxide sequestration, biochemical composition, and theoretical methane potential (TBMP). The findings indicate that C. sorokiniana cultivated with AA produced the highest biomass at 1.62 ± 0.1 g L⁻¹ and a protein content of 47.2 ± 1.8 %. Conversely, PN resulted in the highest lipid content (25.54 ± 1 %). SN demonstrated the most significant methane potential (421 ± 1.9 mL CH₄ g⁻¹ VS) and the highest CO₂ fixation rate (0.18 g CO₂ L⁻¹ d⁻¹), comparable to AA. These findings indicate that AA and SN present distinct advantages compared to other selected nitrogen sources. Specifically, AA enhances both biomass yield and nutrient content, while SN demonstrates superior capabilities in methane production potential and CO₂ fixation. These results emphasize the necessity of judiciously selecting nitrogen sources to optimize the balance between bioenergy production, nutrient utilization, and economic viability in the microalgae cultivation.