Dinoflagellates as sustainable cellulose source: Cultivation, extraction, and characterization

The global demand for manufacturing and consuming biodegradable materials from natural sources has created a great interest in microalgae such as dinoflagellates. Photosynthetic dinoflagellates are a sustainable source of natural materials such as cellulose as they grow using only sunlight and CO2 at near-neutral pH without any fertilizers. In this paper, the cultivation of two species of dinoflagellates (Peridinium sp. and Prorocentrum micans) is established under lab conditions (up to 20 l), cellulose extraction is optimized, and the resulting material is thoroughly characterized. Dinoflagellate cellulose was extracted at room temperature by sequential treatment with highly concentrated 30 % NaOH and 6 M HCl, followed by bleaching with 10 % H2O2. The overall yield of cellulose is around 73 % (w/w), and roughly 85 % of the original dinoflagellate cellulosic morphology remains intact. Chemical purity, morphology, and porosity of the dinoflagellate-derived cellulose are analysed by different characterization techniques (ICP-OES, SEM, XRD, ATR-FTIR, Raman, ssNMR, TGA, BET, and GPC). XRD characterization of the extracted cellulose shows no characteristic reflexes corresponding to a cellulose II allomorph which is mainly amorphous. This result is further supported by ATR-FTIR, Raman, and ssNMR spectroscopy. Overall, these results show that the extracted cellulose is a highly porous, lignin-free material that is thermally stable up to 260 °C. Its high degree of purity and porosity make dinoflagellate-derived cellulose a promising, sustainable candidate for the development of functional hybrid materials for biomedical applications.