Waste to Wealth: Utilizing Digested Banana Waste Media to Enhance Nannochloropsis sp. Production

The astaxanthin-producing green microalga Nannochloropsis sp. has gained significant attention in aquaculture due to its exceptional content of proteins, lipids, and other bioactive compounds. However, the high cost of synthetic culture media limits its large-scale production. This study investigated the digested banana waste media (DBWM) as an alternative, sustainable, and cost-effective culture medium for Nannochloropsis sp. Various concentrations of DBWM (T₂: 10%, T₃: 30%, T₄: 50%, and T₅: 70%) were tested alongside the Bold Basal Medium (BBM) as a control (T₁). Nannochloropsis sp. grown in T₃ achieved the highest growth rate (94.57 × 10⁶ cells/mL) and biomass production (0.670 g/L). This treatment also enhanced pigment accumulation, with an astaxanthin yield of 49.5%. Although higher concentrations (T₄ and T₅) negatively impacted on the growth and pigment synthesis, 30% DBWM also boosted protein and lipid content. Additionally, DBWM-based cultures demonstrated superior efficiency in removing nitrate and phosphate. Cost analysis revealed that DBWM formulations reduced production expenses by up to 3.27 times compared to BBM. These findings demonstrated that DBWM is a cost-effective alternative for the cultivation of Nannochloropsis sp., mitigating the reliance on synthetic media and promoting waste valorization. This circular bioresource strategy offers a globally applicable framework for sustainable microalgal production, contributing to bioeconomic development and environmental sustainability.