Integrated screening and cultivation optimization of food processing wastewater-derived microalgae for enhanced biomass and lipid production toward sustainable biodiesel

Cultivating microalgae in wastewater represents a sustainable strategy for generating lipid-rich biomass for biodiesel production while concurrently achieving wastewater remediation. In this study, green microalgae isolated from food industry wastewater were screened to identify strains with high lipid production potential. The most promising isolate was identified by morphological characteristics and 18S rRNA gene analysis as Coelastrella sp. RMUTSB 01. Comparative cultivation in three types of food industry wastewater showed that wastewater from a processed food production plant (PFPP) supported the highest biomass growth and lipid production. Optimization of wastewater concentration indicated that 60% (v/v) PFPP wastewater was optimal for biomass and lipid production. Further optimization demonstrated that pH 8, 25°C, and a light intensity of 100 µmol photons m⁻ ² s⁻ ¹ maximized growth, yielding biomass and lipid productivities of 70.66 ± 1.89 and 35.51 ± 1.16 mg L⁻ ¹ day⁻ ¹ , respectively. Scale-up cultivation in 2.0-L flasks further increased biomass productivity to 102.79 ± 3.60 mg L⁻ ¹ day⁻ ¹ , with a lipid productivity of 48.80 ± 3.00 mg L⁻ ¹ day⁻ ¹ , and lipid content of 47.47 ± 2.51%. Simultaneously, nutrient and organic pollutant removal efficiencies reached 81–96% for COD, TDS, NH ₃ –N, NO ₃ ⁻, and PO ₄ ³ ⁻. The resulting PUFA-rich fatty acid profile supports both biodiesel production and high-value PUFA applications, highlighting Coelastrella sp. RMUTSB 01 as a promising candidate for integrated wastewater-based lipid production within a sustainable biorefinery framework.