Sustainable Lutein Production from Chlorella sorokiniana NIES-2168 by Using Aquaculture Wastewater with Two-Stage Cultivation Strategies

Abstract

Unnecessary discharge of nutrient-rich aquaculture wastewater is a significant threat to the environment, exacerbating massive resource wasting worldwide. Microalgae-based circular economy strategies utilize atmospheric CO2 and aquaculture wastewater nutrients and convert them into valuable compounds. Lutein, a natural pigment, is a nutritional supplement for eye protection, anti-cancer and anti-inflammatory effects, and other health benefits. It is widely utilized in the food and pharmaceutical industries. The primary purpose of this study is to reuse aquaculture wastewater to grow microalgae and optimize conditions to achieve a high yield of lutein as well as the removal of nutrients from wastewater. When cultured in 1.0× BG11 nutrient-added aquaculture wastewater and aerated using 2% CO2, the biomass concentration and lutein content of Chlorella sorokiniana NIES-2168 increased to 1.78 g L−1 and 7.43 mg g−1, respectively. A two-stage culture strategy further increased the lutein content and yield of microalgae. The highest lutein content of 13.95 mg g−1 and lutein productivity of 3.63 mg L−1 d−1 in the second stage aligned with other phototrophic microalgae currently used for lutein production. C. sorokiniana NIES-2168 also showed exceptional nitrogen and phosphorus removal efficiency, with nitrate and phosphate removal rates reaching 96.07% and 96.75% during the two-stage culture process.