Effect of sub- and supercritical water pretreatment on enzymatic degradation of chitin

We examined the effect of sub- and supercritical water pretreatment (300–400 °C, 0.5–15 min) on enzymatic degradation of chitin to N,N′-diacetylchitobiose (GlcNAc)2. The yield of (GlcNAc)2 by enzymatic degradation of supercritical water pretreated chitin at 400 °C for 1.0 min was up to 37%, compared to 5% without the pretreatment. X-ray diffraction (XRD) analysis revealed that the d-spacing and the crystallite size increased by sub- and supercritical water pretreatment, which is indicative of swelling of the chitin. The swelling of the chitin crystal structure improved enzymatic degradation by allowing the enzymes easy access to the chitin.

► Sub- and supercritical water pretreatment improved enzymatic degradation of chitin to N,N′-diacetylchitobiose (GlcNAc)2. ► The enzymatic degradation ratio after supercritical water pretreatment was 37%, compared to 5% without the pretreatment. ► X-ray diffraction analysis revealed swelling of the chitin occurred in sub- and supercritical water. ► The swelling of the chitin structure improved enzymatic degradation by allowing the enzymes easy access to the chitin.