Tetraselmis chuii: Valorization of dairy wastewater using lactose as an alternative carbon source to...

This study evaluated the direct use of lactose, the main sugar fraction of dairy side-streams, for the mixotrophic cultivation of Tetraselmis chuii. An equimolar glucose/galactose mixture, representing the pre-hydrolysed equivalent of lactose, was included as a comparative treatment. Batch cultures were grown in synthetic media for 10 days at three carbon levels (2.0, 3.5, and 5.0 % w/v), using a photoautotrophic culture as a control. Growth performance, nutrient removal, biochemical productivities, and cell adhesion were assessed. The 3.5 % lactose level showed the best overall performance, achieving a specific growth rate of 0.49 day^-1, a biomass productivity of 1.26 × 10⁵ cells mL^-1 day^-1, and a maximum cell density of 1.50 × 10⁶ cells mL^-1. It also supported a balanced biomass composition, with protein, carbohydrate, fatty acid, and carotenoid productivities of 213, 154.71, 57.29, and 2.63 mg L^-1 day^-1, respectively. In addition, under mixotrophic cultivation, PEG/PDMS coating reduced cell adhesion by approximately 50 % compared with glass. These results highlight the potential of direct lactose use as a carbon source for the mixotrophic cultivation of T. chuii, supporting a sustainable strategy for the valorization of lactose-rich dairy by-products.