Effect of sub- and supercritical water treatments on the physicochemical properties of crab shell chitin and its enzymatic degradation

This study examined the effects of sub- and supercritical water pretreatments on the physicochemical properties of crab shell alpha-chitin and its enzymatic degradation to obtain N,N'-diacetylchitobiose (GlcNAc)(2). Following sub- and supercritical water pretreatments, the protein in the crab shell was removed and the residue of crab shell contained alpha-chitin and CaCO3. Prolonged pretreatment led to alpha-chitin decomposition. The reaction of pure alpha-chitin in sub- and supercritical water pretreatments was investigated separately; we observed lower mean molecular weight and weaker hydrogen bonds compared with untreated alpha-chitin. (GlcNAc)(2) yields from enzymatic degradation of subcritical (350 degrees C, 7 min) and supercritical water (400 degrees C, 2.5 min) pretreated crab shell were 8% and 6%, compared with 0% without any pretreatment. This study shows that sub- and supercritical water pretreatments of crab shell provide to an alternative method to the use of acid and base for decalcification and deproteinization of crab shell required for (GlcNAc)(2) production. (C) 2015 Elsevier Ltd. All rights reserved.