Chitosan-sheath and chitin-core nanowhiskers

Abstract

Chitosan-sheath and α-chitin-core nanowhiskers (CsNWs) have been successfully generated by surface deacetylation of chitin nanowhiskers (CtNWs) in the never-dried state. Acid hydrolysis (3N HCl, 30 mL/g, 104°C) of pure chitin derived from crab shell yielded 65% 4-10nm thick, 16 nm wide and 214 nm long chitin whiskers (CtNWs) that were 86% crystalline and 81% acetylated. Surface deacetylation of CtNWs was robust in their never-dried state in 50% NaOH at a moderate 50°C for 6h, yielding 92% CsNWs. All deacetylated CsNWs retain the same α-chitin crystalline core at reduced 50% crystallinity and similar dimensions (4-12 nm thick, 15 nm wide, 247 long) as CtNWs, but reduced 60% acetylation reflecting the deacetylated surface layers. Progressive surface deacetylation was evident by the increased IP as well as increased positive charges under acidic pH and reduced negative charges at alkaline pH with increasing reaction time.

Structure and Properties of Chitin Whisker Reinforced Papers for Food Packaging Application

“…When chitin was converted to chitin whiskers, the characteristic peaks of the amide groups still existed. The peaks in the chitin whiskers spectrum were sharper than those of crude chitin; this is due to its higher crystallinity (Pereira et al 2014). These FTIR data confirmed that the acid hydrolysis did not alter the chemical nature of α-chitin as expected.…”

“…The increase in crystallinity was due to the removal of the amorphous domain. Whiskers with high crystallinity could provide better reinforcement to the flexible polymeric matrices because of the high modulus of elasticity of the crystal domain (Pereira et al 2014). Note: I represents cellulose fibers, II represents CMC, and III represents chitin whisker % represents the dry mass of chitin per dry mass of paper.…”

The Predominant Molecular State of Bound Enzyme Determines the Strength and Type of Product Inhibition in the Hydrolysis of Recalcitrant Polysaccharides by Processive Enzymes

“…1B). This behavior is consistent with the heterogeneous acetylation of CNWs, with more acetyl groups being introduced to the chitin chains on the surface layers of CNW microcrystals (58). For the subsequent studies, an exponential function was used to calibrate 14 …”

“…Our BMCC and CNW preparations had DP values of 235 and 135 monomer units, respectively. Crystallinity indexes of 86 and 92% have been reported for CNW (58) and BMCC (73), respectively. The parameters of the enzyme kinetics of ChiA and Cel7A are listed in Table 1.…”

“…Although chitin is a polymer of NAG units, chitin preparations always contain a small amount of deacetylated glucosamine units. The degree of acetylation of CNWs prepared from crab chitin was previously estimated to be 81% (58). CNWs were acetylated using [ 14 C]acetic anhydride under heterogeneous conditions to preserve the crystalline nature of the CNWs.…”