Sustainable biorefinery of Ulva stenophylloides, a green-tide species from the South Pacific coast: A study on antioxidant, oligosaccharide, and ulvan extraction

In this study, biomass characterization and sustainable biorefinery were determined using microwave-assisted extraction to recover valuable biocompounds from the green-tide species Ulva stenophylloides. The biomass exhibits concentrations of 21 % for proteins; 24.6 % for sulfate; 2.1 % for lipids; 27 % for carbohydrates; 15 % and 11 % for chlorophylls a and b, respectively; and 4.6 % for carotenoids. The temperature of the microwave treatment influenced both the yield and quality of biocompounds, with higher concentrations of phenolic compounds and antioxidant activities observed in the soluble extracts at temperatures between 180 °C and 220 °C, and higher concentrations of oligosaccharides obtained at temperatures from 120 °C to 200 °C. Microwave treatment at 120 °C yielded the highest content of ulvans (21 %), as well as favorable molecular weight and viscoelastic properties. Furthermore, the ulvan extract demonstrated no toxic effect in both in vitro and in vivo toxicological assays. These findings highlight the potential of green tides as a renewable biomass source for various biocompounds, opening up possibilities for future biotechnology research.