Sustainable production of nanocrystalline cellulose from Sargassum spp. biomass via deep eutectic solvents: A comparative study of green methodologies

This study explores a novel approach to valorizing Sargassum spp. biomass as a renewable source for isolating nanocellulose through a circular economy approach, addressing a critical environmental and economic problem in the Mexican Caribbean. Conventionally, nanocellulose isolation is performed through physical and chemical treatments. However, these methods often involve harsh chemicals and high energy consumption. To reduce environmental impact, three methodologies for isolating crystalline and nanofibrillated nanocellulose were compared, aiming for a process with minimal waste and a significant reduction in hazardous chemicals, using a deep eutectic solvent made of chloride and oxalic acid. We tested a modified Acetosolv method combined with a deep eutectic solvent (ADES), a continuous ADES (cADES), and a free-acetic-acid method using only the deep eutectic solvent (extDES). The ADES method demonstrated the highest efficacy in producing nanocellulose with exceptional purity and crystallinity (~86%), with an isolation yield of 12-15%. Notably, the extDES method emerged as a breakthrough, successfully producing carboxylated nanocellulose (carboxylate content around 1.24 mmol g -1 ) without the use of acetic and sulfuric acids. The chemical and physical properties of the samples demonstrate that the proposed methodologies are competitive with conventional approaches, enhancing swelling capacity, crystallinity index, and nanocellulose functionalization, without requiring additional processing steps. Isolated nanocellulose by ADES exhibits valuable non-cytotoxic (cell viability > 95% across all evaluated lines) and anti-inflammatory (73–92% inhibition at lower concentrations than diclofenac) properties, making it a potential material for applications in the biomedical and advanced functional materials sectors. • Sargassum is a renewable resource for producing cellulose nanocrystals and nanofibers • Sustainable DES-based methodologies were competitive with conventional ones • ADES methodology produces pure and highly crystalline nanocellulose (~86%) • DES-treated nanocellulose shows high anti-inflammatory activity (~92% inhibition) • Nanocellulose obtained by ADES did not show cytotoxicity (cell viability >95%)