Cultivation of Auxenochlorella protothecoides using tofu whey wastewater for aquaculture feed production: Integrating resource recovery and microalgal biomass valorization strategy

This study investigates the potential of utilizing tofu whey wastewater (TWW) for Auxenochlorella protothecoides cultivation and aquatic protein feed production. Results demonstrate that A. protothecoides cultured in TWW (AP-C-TWW) achieves biomass and protein yield of 16.45 g/L and 8.84 g/L, respectively, representing 78 % and 85 % increases compared to conventional medium. AP-C-TWW exhibits an essential-to-nonessential amino acid ratio of 0.7, fulfilling protein feed standards. Whilst TWW treatment with A. protothecoides results in the removal of 88 %, 96 %, and 99 % of total phosphorus, total nitrogen, and chemical oxygen demand, respectively, ensuring compliance with discharge regulations. Furthermore, replacing 5 % of dietary fishmeal with AP-C-TWW increases the final body weight and specific growth rate of Oncorhynchus mykiss by 10 % and 13 %, respectively, compared to control group. Additionally, it significantly enhances antioxidant capacity, innate immunity, and fillet quality. This study highlights the potential of TWW upcycling for sustainable microalgae-based aquaculture feed production.