Abstract:Non-catalytic synthesis of 4-O-β-2-acetamido-2-deoxy-d-glucopyranosyl 2-acetamido-2,3-dideoxydidehydro-glucopyranose (GND) from chitin disaccharide, N,N′-diacetylchitobiose (GlcNAc)2, was achieved, with a maximum yield of 24.7% in high-temperature water at 120–220 °C and 25 MPa with a reaction time of 8–39 s.
“…5 (c). The low-molecular weight chitin chains are immediately dehydrated at the reducing end, reported in our previous study (Osada et al, 2014). We observed that the dehydration of (GlcNAc)2 proceeded at temperatures above 180°C for 1 min, altering the chemical structure of GlcNAc unit.…”
Section: Effects Of Sub-and Supercritical Water Treatments On the Prosupporting
confidence: 66%
“…For GlcNAc, the dehydration proceeds between H-2 and OH-3 because the N-acetyl group is an electron-withdrawing group and the elimination of H-2 takes place easier, as compared with glucose. We also reported that the dehydration of (GlcNAc)2 is promoted at the reducing end of (GlcNAc)2 at lower temperatures of around 200°C, as compared with cellobiose (Osada et al, 2014). We have reported these findings in our previous studies that were focused on the dehydration of GlcNAc and (GlcNAc)2 in subcritical water at around 200°C.…”
Section: Effects Of Sub-and Supercritical Water Treatments On the Prosupporting
This study examined the effects of sub-and supercritical water pretreatments on the physicochemical properties of crab shell α-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 α-chitin and CaCO3. Prolonged pretreatment led to α-chitin decomposition. The reaction of pure α-chitin in sub-and supercritical water pretreatments was investigated separately; we observed lower mean molecular weight and weaker hydrogen bonds compared with untreated α-chitin.(GlcNAc)2 yields from enzymatic degradation of subcritical (350C, 7 min) and supercritical water (400C, 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.
“…5 (c). The low-molecular weight chitin chains are immediately dehydrated at the reducing end, reported in our previous study (Osada et al, 2014). We observed that the dehydration of (GlcNAc)2 proceeded at temperatures above 180°C for 1 min, altering the chemical structure of GlcNAc unit.…”
Section: Effects Of Sub-and Supercritical Water Treatments On the Prosupporting
confidence: 66%
“…For GlcNAc, the dehydration proceeds between H-2 and OH-3 because the N-acetyl group is an electron-withdrawing group and the elimination of H-2 takes place easier, as compared with glucose. We also reported that the dehydration of (GlcNAc)2 is promoted at the reducing end of (GlcNAc)2 at lower temperatures of around 200°C, as compared with cellobiose (Osada et al, 2014). We have reported these findings in our previous studies that were focused on the dehydration of GlcNAc and (GlcNAc)2 in subcritical water at around 200°C.…”
Section: Effects Of Sub-and Supercritical Water Treatments On the Prosupporting
This study examined the effects of sub-and supercritical water pretreatments on the physicochemical properties of crab shell α-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 α-chitin and CaCO3. Prolonged pretreatment led to α-chitin decomposition. The reaction of pure α-chitin in sub-and supercritical water pretreatments was investigated separately; we observed lower mean molecular weight and weaker hydrogen bonds compared with untreated α-chitin.(GlcNAc)2 yields from enzymatic degradation of subcritical (350C, 7 min) and supercritical water (400C, 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.
“…All bleached chitosan also appeared darker than their respective bleached chitins, especially the chitosan of dead adults and pupal exuviae. This browning is probably due to the high temperatures used for the deacetylation reaction, inducing some saccharide dehydration leading to double bonds formation 83 , 84 . Figure 2 (a) FTIR spectra of both unbleached (A,C) and bleached (B,D) chitin (A,B) and chitosan (C,D) samples extracted from H. illucens larvae (red line), pupal exuviae (blue line) and dead adults (black line).…”
Due to their properties and applications, the growing demand for chitin and chitosan has stimulated the market to find more sustainable alternatives to the current commercial source (crustaceans). Bioconverter insects, such as Hermetia illucens, are the appropriate candidates, as chitin is a side stream of insect farms for feed applications. This is the first report on production and characterization of chitin and chitosan from different biomasses derived from H. illucens, valorizing the overproduced larvae in feed applications, the pupal exuviae and the dead adults. Pupal exuviae are the best biomass, both for chitin and chitosan yields and for their abundance and easy supply from insect farms. Fourier-transform infrared spectroscopy, X-ray diffraction and scanning electron microscope analysis revealed the similarity of insect-derived polymers to commercial ones in terms of purity and structural morphology, and therefore their suitability for industrial and biomedical applications. Its fibrillary nature makes H. illucens chitin suitable for producing fibrous manufacts after conversion to chitin nanofibrils, particularly adults-derived chitin, because of its high crystallinity. A great versatility emerged from the evaluation of the physicochemical properties of chitosan obtained from H. illucens, which presented a lower viscosity-average molecular weight and a high deacetylation degree, fostering its putative antimicrobial properties.
“…5), which is probably due to the partial decomposition of βchitin. [35][36][37] At 250 °C for 30 min, the weight change and protein yield are 30% and 60%, respectively, indicating that 0% of the protein remains in the solid residue. However, distributing the NF width at 250 °C for 30 min differs from that of reagent β-ChNF (Fig.…”
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