Valorization of Chrysanthemum juice as cultivation medium for the microalga Tetradesmus obliquus: a proof-of-concept study at pilot-scale

To make the production of certain feedstocks more sustainable, a more circular economy is warranted. One such example is the approach in which green waste biomasses are processed by separating the solid (fiber) fraction from the liquid (juice) fraction to use both fractions as feedstocks for different applications. The liquid fraction can potentially be used as an alternative for mineral medium for algal cultivation. However, little research has so far been done on the implementation of such approach in the production process of microalgae. To provide more insights in this, the potential of flower juice as an alternative for mineral medium was tested to grow microalgae with an emphasis on the potential of using the algal biomass as feed. For this Tetradesmus obliquus was cultivated in the juice of Chrysanthemum , the most cultivated ornamental plant in the Netherlands. Both laboratory and pilot-scale cultivation showed the potential of the Chrysanthemum juice as a replacement for mineral medium. The algal biomass composition in the pilot-scale test showed to be similar to previously reported studies with a protein content up to 58% and a lipid content up to 18% based on dry weight. While the total obtained dry weight, in our study, was lower in the Chrysanthemum juice based medium (0.4 g/L) compared to the mineral medium (0.8 g/L), the extended pilot-scale cultivation showed adaptation of the algae to the Chrysanthemum juice indicating the potential of using this flower juice as a more sustainable alternative for mineral medium. However, more research into the microbial load and presence of pesticides in the algal biomass after growth on the Chrysanthemum juice based medium should be performed.