Paper Title
Optimization of Growth and Lipid Production In Nannochloropsisoculata ISRC-P007: The Role of Salinity, Nutrient Sources, and Contamination Impact

Abstract
Marine microalgae such as Nannochloropsis species are promising candidates for biofuel production due to their high lipid content and rapid growth rates. This study investigates the optimization of growth conditions and lipid production in Nannochloropsisoculata ISRC-P007, a strain native to the Persian Gulf. The optimization process focused on evaluating the effects of salinity, carbon, and nitrogen sources using the Taguchi method to enhance growth rates cost-effectively. The optimized conditions were identified as a salinity of 30 g L⁻¹, ammonium chloride as the nitrogen source, and sodium acetate as the carbon source. Under these conditions, the strain achieved a maximum exponential growth rate of 0.537 d⁻¹, confirmed through statistical validation. Lipid extraction was performed at different growth stages, with nitrogen depletion during the stationary phase yielding the highest lipid content. The impact of contamination by Heterocystous Filamentous Cyanobacteria (HFC) was also assessed. Contaminated cultures exhibited higher biomass but lower lipid productivity compared to pure cultures, with notable differences in fatty acid profiles. Specifically, the content of C16:1, C18:0, C18:1, C20:4, and C20:5 varied significantly between pure and contaminated cultures, demonstrating the influence of HFC contamination on lipid composition. The study underscores the importance of optimizing environmental parameters and nutrient sources to enhance microalgal growth and lipid production while considering the implications of contamination in large-scale production systems. Keywords - Microalgae, Lipid production, Biodiesel, Fatty acid profile