Abstract text: Algae share key features with land plants, including the ability to photosynthesise, and possession of polysaccharide-rich cell walls. Many green algal cell walls include polysaccharides such as cellulose and xyloglucans, better known from land plants. Ulva sp. also produce ulvan, a commercially valuable polysaccharide renowned for its antiviral, anticoagulant, antitumor and anti-inflammatory properties. Commercial exploitation demands that cultivation is optimised to ensure a consistent and high-quality biomass.

To identify the optimal light intensity, temperature and salinity parameters for polysaccharide biosynthesis, indoor experiments were conducted at CTAQUA (Cadiz, Spain) on U. cf. flexuosa and U. ohnoi. Carbohydrate content was quantified using the Dubois assay, following extractions with ethanol and hydrochloric acid (0.01 M), and fractionation into soluble sugars, hemicelluloses + ulvan, and cellulose.

Preliminary results suggest a significant decrease in the carbohydrate content of U. ohnoi with increasing salinity. While increased irradiance is positively correlated with growth in both species, the soluble sugar content of U. flexuosa decreases. In contrast, irradiance appeared to have little impact on the carbohydrate content of U. ohnoi. These results emphasize the importance of evaluating the impact of growth parameters to find the sweet spot of growth and carbohydrate yield for specific Ulva species.