Heterotrophic culture of Scenedesmus almeriensis for lutein productivity enhancement

The green microalga Scenedesmus almeriensis shows promise for natural carotenoid production, specifically lutein, a pigment inducing health benefits, often lacking in the human diet. In this study, S. almeriensis was successfully cultured heterotrophically for the first time. Heterotrophic biomass accumulation and pigment productivity were compared to a phototrophic culture, and a period of photoinduction followed the heterotrophic culture to stimulate carotenoid pigment synthesis. Under optimal glucose and sodium nitrate levels, the heterotrophic culture achieved a cell density of 22 g L^–1 Lutein and violaxanthin contents were 2.2 and 1.5 times higher in the phototrophic culture compared to the heterotrophic culture, while zeaxanthin content was 1.8 times higher in the heterotrophic culture. However, heterotrophic culture exhibited higher productivity for lutein, violaxanthin, and zeaxanthin, with 9.79, 2.08, and 2.46 mg L^–1 day^–1, respectively. Additionally, the photoinduction stage enhanced carotenogenesis and increased productivity, reaching productivities of 11.52, 4.56, and 5.09 mg L^–1 day^–1 for lutein, violaxanthin, and zeaxanthin, respectively. These promising findings indicate the potential of S. almeriensis in heterotrophic culture for carotenoid production.