Eco-friendly biorefinery process optimization from Sargassum thunbergii: A sustainable approach toward zero waste

This study explores the eco-friendly extraction of functional compounds from underutilized marine biomass, specifically on , using the subcritical water treatment (SWT) technique. We aim to achieve complete valorization in a sustainable biorefinery process that generates zero waste. Employing response surface methodology, we identified optimal extraction conditions for maximizing the yield of total phenolic content from . The optimal conditions were determined to be a temperature of 195.43 °C, a reaction time of 18.82 min, and a solid/liquid ratio of 0.032 g/mL. The optimized extract (OSE) was analyzed, revealing a total phenol content of 29.01 ± 0.28 mg phloroglucinol equivalent/g and a total flavonoid content of 10.33 ± 0.48 mg quercetin equivalent/g. Ultra-performance liquid chromatography–electrospray ionization quadrupole time-of-flight mass spectrometry revealed 64 phenolic compounds, including phenolic acids, flavonoids, and other polyphenols. Nuclear magnetic resonance spectroscopy confirmed the presence of polysaccharides and phenolic compounds in OSE. Furthermore, residue analysis indicated the potential for biofuel production from the remaining biomass, contributing to a zero-waste biorefinery process. This study establishes a theoretical foundation and provides practical guidelines for the efficient extraction and processing of phenolic compounds from , indicating the feasibility of a sustainable biorefinery process using SWT.