Recovery of organic nutrients by Chlorella sorokiniana CMBB276 under various light qualities in aquaculture wastewater

Light quality plays a crucial role in biomass production, biochemical composition, and nutrient removal efficiency in microalgae-based wastewater treatment systems. However, its effects in organic aquaculture wastewater systems remain underexplored. This study investigated the responses of Chlorella sorokiniana CMBB276 to six light qualities (red, blue, white, mixed, red-to-blue, and red-to-mixed) in a system where dissolved organic nitrogen (DON) and phosphorus (DOP) accounted for 83.50 % of total nitrogen and 88.30 % of total phosphorus, respectively. Among the treatments, red light produced the highest biomass (1.54 g L^-1), significantly exceeding the biomass achieved under blue light, which yielded the lowest value (0.61 g L^-1) on day 16-only 40 % of the yield observed under red light. Additionally, organic matter removal efficiency followed the hierarchy: red light/red-to-mixed/red-to-blue > mixed light > blue light > white light. Across all light treatments, dissolved organic matter (DOM) transformation involved reduced tyrosine-like substances (C1) and increased humic-like substances (C2, C4), with variations in organic matter degradation and growth dynamics. In terms of biochemical composition, protein accumulation was highest under blue light at 30.10 % dry weight (DW), while carbohydrate content peaked under red-inclusive lights, reaching 52.41 % DW under red-to-blue light. These findings demonstrate the potential of C. sorokiniana for nutrient removal and biomass production in aquaculture wastewater, providing insights for optimizing sustainable aquaculture practices.