Nanocrystalline Cellulose from the Solitary Tunicate Phallusia Mammillata, a Valuable Nanocellulose Precursor

Ascidians are ubiquitous filter-feeding marine invertebrates, the only animals producing cellulose in their outer tunic, in the form of a composite structure of cellulose microfibrils linked to a protein matrix. This study reports the successful processing of Phallusia mammillata, a species prevalent in the Northern Adriatic Sea, into high-quality nanocellulose (NC). An optimized extraction method followed by chemical modification is applied to produce suitable precursors for cellulose-based products. Structural, compositional, and thermal characterization demonstrated the high degree of crystallinity of the extracted cellulose, which is further processed into both cationic and anionic forms by direct reaction of nanofibril suspensions. High-aspect-ratio nanofibrillated cellulose (NFC) with a fibrils diameter of 10 +/- 2 nm is directly obtained from purified tunics. Anionic nanocrystals and cationic nanofibrils with a mean diameter of 8 +/- 2 nm are obtained from pristine nanofibrillated cellulose suspensions. To the best of the authors' knowledge, this is the first report on the extraction and processing of cellulose from Phallusia mammillata, opening new possibilities toward high-grade cellulose-based materials exploiting an abundant local resource.