The comparison of the properties of nanocellulose isolated from colonial and solitary marine tunicates

This is the first comparative of tunicate cellulose nanocrystalline (t-CNC) from colonial and solitary tunicates. The t-CNC from the colonial tunicate Eudistoma sp. (CL1) was compared with solitary tunicates Polycarpa reniformis (CL2) and Phallusia nigra (CL3). Tunicate samples were extracted by methanol. Residues from the methanol extraction were then subjected to further cellulose purification using pre-hydrolysis, kraft-cooking, bleaching, and sulfuric acid hydrolysis to yield t-CNC. The solitary tunicates yielded higher microfibril contents after the bleaching step but obtained similar t-CNC content to the colonial one after acid hydrolysis. The isolated t-CNC were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, thermalgravimetric analysis, and transmission electron microscopy. Both colonial and solitary tunicates yielded cellulose type I. The pure cellulose type I was successfully isolated from solitary tunicates whereas high inorganic impurities were observed in colonial tunicates. The isolate t-CNC showed high aspect ratios. The solitary and colonial tunicates provided t-CNC with crystallinity indexes over 97% and 35%, respectively. The crystalline size of t-CNCs ranged from 55-124 Å. The thermal stability of all isolated t-CNC was slightly decreased due to the sulfate functional groups gained after acid hydrolysis. We concluded that solitary tunicates were better than colonial tunicates as a source of t-CNC preparation.