Acid Hydrolysis Of Chitin Research Articles

Acid hydrolysis of chitin in calcium chloride solutions

This work describes a mild aging-hydrolysis integrated approach to selectively produceN-acetyl-d-glucosamine from chitin in cheap and abundant CaCl2-based molten salt hydrate solvents.

Characterization of glucose-crosslinked gelatin films reinforced with chitin nanowhiskers for active packaging development

To find renewable and sustainable alternatives to reduce the severe environmental impact of single-use synthetic plastic packaging, glucose-crosslinked gelatin films containing different amounts of chitin nanowhiskers (CNWs) were prepared. CNWs were first prepared by acid hydrolysis of chitin from shrimps, and characterized (morphological and thermal properties), before their addition into film-forming formulations. The films were heat-treated to promote the chemical crosslinking Maillard reaction (MR), between glucose and gelatin. The films then became less soluble (from 100% to ∼10%), thermally more stable, had a notably improved UV–vis light absorption capacity, and presented significantly enhanced tensile strength (from 42 to 77 MPa) and Young's modulus (from 1476 to 2921 MPa), however, they also became less flexible (from 17% to 7%) and transparent. These property alterations were mainly related to changes in crystallinity, the MR and to a lesser extent, to the formation of noncovalent (electrostatic and hydrogen bonding) interactions between CNWs and gelatin. Furthermore, due to the formation of MR products, the films turned yellow/dark brown and released antioxidant compounds (inhibition ∼33%) while immersed in water, which gave the films their active properties (stabilization of free radicals). These films have considerable potential as reinforced active packaging films for renewable food packaging applications.

Recovery of glucosamine and optimization of chitin extraction with acid and alkali process from shells of sea mussel Mytilus galloprovincialis in Greece

Mussel wastes include byproducts such as seed, barnacles fouling, broken shells, byssus threads, which are associated with serious environmental impacts on aquatic ecosystems. The objective of reducing wastes and to avoid environmental problems can be achieved by establishing alternative methods to valorize mussel wastes converting them into high value-added products. The present study aims to obtain by chemical methods the extraction of chitin and glucosamine from shells of Mytilus galloprovincialis. Chitin, which chemically is a linear polysaccharide of β (1→4) linked N-acetylglucosamine monomers, possesses multifunctional properties and is suitable for various applications mainly in pharmaceutical, biomedical food and packaging fields. Glucosamine (C6H13NO5) is an amino sugar (2-amino-2-deoxy-β-D-glucopyranose) and is a part of the structure of two polysaccharides, chitosan and chitin. Due to its high aqueous solubility and physical stability is used as a potential solid-dispersion carrier to improve the biopharmaceutical properties of drugs. The influence of temperature, solid/liquid ratio (g/ml), molarity of solutions and agitation on chitin production and acid hydrolysis of chitin was studied to achieve optimum output of chitin and glucosamine. Our results demonstrates that the production of glucosamine and chitin is greatly influenced by the experimental conditions. The best yield for glucosamine was obtained at a solid/liquid ratio of 1:15 at 60°C for 1 hour.

HPLC Analysis of N-acetyl-chito-oligosaccharides during the Acid Hydrolysis of Chitin

The hydrolysis of chitin (93% N-acetylation) by hydrochloric acid produced N-acetylchito-oligosaccharides (NACOs) with low degrees of polymerization (DP) from 2 to 6. The HPLC retention time of NACOs decreased with increased water content in the mobile phase. A gradient elution procedure, using acetonitrile to water (v/v) ratio lowered linearly from 80/20 to 60/40 within 60 min, provided optimal resolution and characterization for the NACOs. The natural logarithm of the retention time of NACOs correlated linearly with the DP values. Hydrolysis of chitin followed a series-parallel reaction mechanism. At the same time the NACOs with higher DP's were generated from chitin, and were degraded by hydrochloric acid to form products with lower DP's. More NACOs with higher DP's were produced under conditions with higher concentrations of hydrochloric acid and a shorter reaction period. Higher temperatures facilitated the generation of NACOs with lower DP's.

Kinetic Models for Glucosamine Production by Acid Hydrolysis of Chitin in Five Mushrooms

In this paper, glucosamine was produced by acid hydrolysis of five mushrooms. The glucosamine yields were investigated, and the optimum conditions were obtained as follows: acid type, sulfuric acid; acid concentration, 6 M; ratio of raw material to acid volume, 1 : 10; hydrolysis temperature, 100°C; and time, 6 h. Under these conditions, the glucosamine conversion from chitin content reached up to 92%. The results of hydrolysis kinetics indicated that hydrolysis of five mushrooms to glucosamine followed zero-order kinetics. Moreover, the relatively low activation energy for hydrolysis of straw mushroom (18.31 kJ/mol) and the highest glucosamine yield (56.8132 ± 3.5748 mg/g DM, 0.9824 g/g chitin) indicated that hydrolysis of straw mushroom was energy-saving. Thus, sulfuric acid hydrolysis of straw mushroom for glucosamine production should be considered as an efficient process for the future industrial application. However, further study is needed for glucosamine purification.

Chemically Cross-Linked Chitin Nanocrystal Scaffolds for Drug Delivery

Chitin nanocrystals (ChNCs), prepared by acid hydrolysis of chitin, exhibit a uniform needlelike morphology and high dispersion stability in aqueous solutions, which makes them good candidates for ...

Metabolic engineering for the production of chitooligosaccharides: advances and perspectives.

Chitin oligosaccharides (CTOs) and its related compounds chitosan oligosaccharides (CSOs), collectively known as chitooligosaccharides (COs), exhibit numerous biological activities in applications in the nutraceutical, cosmetics, agriculture, and pharmaceutical industries. COs are currently produced by acid hydrolysis of chitin or chitosan, or enzymatic techniques with uncontrollable polymerization. Microbial fermentation by recombinant Escherichia coli, as an alternative method for the production of COs, shows new potential because it can produce a well-defined COs mixture and is an environmentally friendly process. In addition, Bacillus subtilis, a nonpathogenic, endotoxin-free, GRAS status bacterium, presents a new opportunity as a platform to produce COs. Here, we review the applications of COs and differences between CTOs and CSOs, summarize the current preparation approaches of COs, and discuss the future research potentials and challenges in the production of well-defined COs in B. subtilis by metabolic engineering.

Isolation and Characterization of Chitin Nanowhiskers from Fermented Tiger Prawn Waste

The objective of this study is to produce chitin nanowhiskers (CNW) from bacterial fermentation of tiger prawn waste. For this purpose, chitin was first extracted from tiger prawn waste using bacterial fermentation process followed by isolation of CNW using acid hydrolysis process. The isolated CNW from fermented tiger prawn waste (FCNW) were investigated using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), x-ray diffractometer (X-RD) and thermogravimetric analysis (TGA). FTIR spectra analysis indicates that the acid hydrolysis of chitin did not altered the chemical structure of isolated FCNW. TEM analysis revealed that the produced FCNW displayed a nanoscale structure with an average length and width of 100 and 10 nm. AFM images of FCNW indicate the presence of spindle-like features. The X-RD analysis revealed that the acid hydrolysis process enhanced the crystallinity of FCNW from 20 to 46 % compared to chitin due to the removal of the amorphous region. The TGA results revealed that the FCNW is more thermally stable than fermented chitin (FC) and CNW from commercial chitin. The relatively good thermal stability of FCNW shows its suitability in a range of applications such as reinforcing fillers in green nanocomposites.

Bio-inspired production of chitosan/chitin films from liquid crystalline suspensions

Inspired by chitin based hierarchical structures observed in arthropods exoskeleton, this work reports the capturing of chitin nanowhiskers’ chiral nematic order into a chitosan matrix. For this purpose, highly crystalline chitin nanowhiskers (CTNW) with spindle-like morphology and average aspect ratio of 24.9 were produced by acid hydrolysis of chitin. CTNW were uniformly dispersed at different concentrations in aqueous suspensions. The suspensions liquid crystalline phase domain was determined by rheological measurements and polarized optical microscopy (POM). Chitosan (CS) was added to the CTNW isotropic, biphasic and anisotropic suspensions and the solvent was evaporated to allow films formation. The Films’ morphologies as well as the mechanical properties were explored. A correlation between experimental results and a theoretical model, for layered matrix’ structures with fibers acting as a reinforcement agent, was established. The results evidence the existence of two different layered structures, one formed by chitosan layers induced by the presence of chitin and another formed by chitin nanowhiskers layers. By playing on the ratio chitin/chitosan one layered structure or the other can be obtained allowing the tunning of materials’ mechanical properties.

Preparation, characterization, and antimicrobial activity of chitin nanofibrils reinforced carrageenan nanocomposite films.

Present study illustrates the preparation of chitin nanofibrils (CNF) reinforced carrageenan nanocomposite films by the solution-casting technique. CNF was prepared by acid hydrolysis of chitin, followed by high speed homogenization and sonication. FTIR result demonstrated that the chemical structure of chitin had not changed after acid hydrolysis. However, the crystalinity of CNF was found to be higher than chitin. The crystallite size of chitin and CNF was 4.73 and 6.27 nm, respectively. The char content at 600 °C of chitin (19.2%) was lower than the CNF (25%). The carrageenan/CNF composite films were smooth and flexible and the CNF was dispersed uniformly in the carrageenan polymer matrix. The tensile strength and modulus of carrageenan film were increased significantly (p<0.05) after CNF reinforcement with up to 5 wt%, however, elongation at break, water vapor permeability, and transparency decreased slightly. Carrageenan/CNF nanocomposite films showed strong antibacterial activity against a Gram-positive food-borne pathogen, Listeria monocytogenes.

Interactions of chitin nanocrystals with β-lactoglobulin at the oil–water interface, studied by drop shape tensiometry

Particle stabilized emulsions have been gaining increasing attention in the past few years, because of their unique interfacial properties. However, interactions between food grade particles and other surfactants at the interface still need to be understood. In this research, the interfacial properties of chitin nanocrystals (ChN) were studied in the presence of a surface active milk protein, β-lactoglobulin (β-lg), often used to stabilize oil-in-water emulsions. ChN were prepared by acid hydrolysis of chitin. At low pH (pH 3), ChN and β-lg do not interact, as demonstrated by light scattering measurements, and both components carry positive charge. The properties of the interface were tested using drop shape tensiometry. Addition of ChN or β-lg to the aqueous phase reduced the interfacial tension, and β-lg adsorption was characterized with an increase in the interfacial elasticity. When β-lg was added to a solution containing 0.1% ChN, the film elasticity increased first and then decreased with increasing β-lg concentration. The mixed film elasticity was the highest at a combination of 0.1% ChN+0.01% β-lg, when both molecules were simultaneously added to the aqueous phase. On the other hand, when β-lg was added after ChN, the protein did not affect the properties of the interface, indicating that the ChN (0.1%) equilibrated film was stable and that protein–protein interactions, normally resulting in an increase in the film elasticity, did not occur.

Microbial production of glucosamine and N-acetylglucosamine: advances and perspectives

Glucosamine (GlcN), an amino sugar, is a compound derived from substitution of a hydroxyl group of a glucose molecule with an amino group. GlcN and its acetylated derivative, N-acetylglucosamine (GlcNAc), have been widely used in food, cosmetics, and pharmaceutical industries and are currently produced by acid hydrolysis of chitin (a linear polymer of GlcNAc) extracted from crab and shrimp shells. Microbial fermentation by filamentous fungi or recombinant Escherichia coli, as an alternative method for the production of GlcN and GlcNAc, is attracting increasing attention because it is an environmentally friendly process. Although the microbial production of GlcN and GlcNAc is hampered by low yield and high production cost, considerable advances have been made in recent years. Here we review the applications, commercial market, and production of GlcN and GlcNAc, with emphasis on the metabolic and process engineering strategies used to improve GlcN and GlcNAc production by recombinant microbes.

Interfacial interaction and mechanical properties of chitin whisker–poly(vinyl alcohol) gel‐spun nanocomposite fibers

AbstractNanocomposite fibers were prepared from chitin whiskers (ChWs) as the reinforcing phase and poly(vinyl alcohol) (PVA) as the matrix. Colloidal suspensions of ChWs, obtained by acid hydrolysis of chitin from crab shell, were thoroughly mixed with aqueous PVA. The homogeneous PVA–ChW suspensions were gel‐spun into a methanol coagulating bath. Wide‐angle X‐ray diffraction patterns evidenced the orientation of ChWs along the fiber axis. From differential scanning calorimetry, the crystallinity of the PVA component was found to increase with ChW loading due to the possible dragging of PVA chains adhering to ChWs during vertical extrusion. The non‐isothermal crystallization peak of PVA was observed to shift to lower temperature with ChW loading indicating interfacial interactions between PVA and ChW. Further interaction between PVA and ChW was evidenced by the shifting of the Fourier transform infrared bands of PVA to lower wavenumber and the dynamic tan δ peak, corresponding to α‐relaxation of PVA, shifting to higher temperature. The interaction of ChWs with the matrix PVA yielded a significant enhancement in the mechanical properties of the nanocomposites. Copyright © 2012 Society of Chemical Industry

Conjugates of Bovine Serum Albumin with Chitin Oligosaccharides Prepared through the Maillard Reaction

Chitin neoglycoconjugates (BSA-CO) were obtained by the conjugation of bovine serum albumin (BSA) with chitin oligosaccharides (CO) through the Maillard reaction (nonenzymatic glycation). CO produced by acid hydrolysis of chitin were fractionated using an ultrafiltration membrane system (1-3 kDa cutoff). The Maillard reaction was carried out by heating a freeze-dried mixture containing BSA and CO at 60 °C (under 43% relative humidity for 6 and 12 h). BSA-CO were characterized by available amino groups content, intrinsic tryptophan emission spectra, gel electrophoresis, and mass spectrometry. Biological assays included interaction with wheat germ agglutinin (WGA) and with bacterial adhesins of Escherichia coli K88+ and Salmonella choleraesuis. Glycation of BSA was revealed by reduction of available amino groups and fluorescence intensity and also retarded migration through SDS-PAGE. Conjugation of BSA with chitin oligomers appeared to be time dependent and was confirmed by mass spectrometry, by which molecular mass increase for monomers and dimers was observed. Monomers were estimated to contain either one or two glycation sites (at 6 and 12 h of treatment, respectively), with one or two tetrasaccharide units attached. Consequently, dimers showed two or four glycation sites. BSA-CO presented biological recognition by WGA and E. coli K88+ and S. cholerasuis adhesins. The strategy used in this work represents a simple method to obtain glycoconjugates to study applications involving protein-carbohydrate recognition.

Fabrication, structure, and properties of chitin whisker‐reinforced alginate nanocomposite fibers

AbstractCalcium alginate yarn (30 fibers) and calcium alginate nanocomposite yarn (30 fibers) containing 0.05–2.00% w/w chitin whiskers were both prepared by wet spinning process. The whiskers were prepared by acid hydrolysis of chitin from shrimp shells. The average length and width of the whiskers were 343 and 46 nm, with the aspect ratio being ∼ 7.5. Incorporation of a low amount of the whiskers in the nanocomposite fibers improved both the mechanical and the thermal properties of the fibers significantly, possibly a result of the specific interactions, i.e., hydrogen bonding and electrostatic interactions, between the alginate molecules and the homogeneously dispersed chitin whiskers. Biodegradation of the calcium alginate fibers and the nanocomposite fibers was tested in Tris‐HCl buffer solution and the same buffer solution that contained lysozyme. The addition of the chitin whiskers in the nanocomposites fibers accelerated the biodegradation process of the fibers in the presence of lysozyme, whereas the presence of Ca2+ ions in the Tris‐HCl buffer solution helped to improve the tenacity of both the alginate and the nanocomposite fibers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Metabolic engineering of Escherichia coli for industrial production of glucosamine and N-acetylglucosamine

Glucosamine and N-acetylglucosamine are currently produced by extraction and acid hydrolysis of chitin from shellfish waste. Production could be limited by the amount of raw material available and the product potentially carries the risk of shellfish protein contamination. Escherichia coli was modified by metabolic engineering to develop a fermentation process. Over-expression of glucosamine synthase (GlmS) and inactivation of catabolic genes increased glucosamine production by 15 fold, reaching 60 mg l −1. Since GlmS is strongly inhibited by glucosamine-6-P, GlmS variants were generated via error-prone PCR and screened. Over-expression of an improved enzyme led to a glucosamine titer of 17 g l −1. Rapid degradation of glucosamine and inhibitory effects of glucosamine and its degradation products on host cells limited further improvement. An alternative fermentation product, N-acetylglucosamine, is stable, non-inhibitory to the host and readily hydrolyzed to glucosamine under acidic conditions. Therefore, the glucosamine pathway was extended to N-acetylglucosamine by over-expressing a heterologous glucosamine-6-P N-acetyltransferase. Using a simple and low-cost fermentation process developed for this strain, over 110 g l −1 of N-acetylglucosamine was produced.

Acid Hydrolysis of Chitin and Chitosan

Acid hydrolysis of chitin and chitosan recovered from shells of sea Crustacea was studied by exclusion high-performance liquid chromatography.

Crab shell chitin whisker reinforced natural rubber nanocomposites. 1. Processing and swelling behavior.

Nanocomposite materials were obtained from a colloidal suspension of chitin whiskers as the reinforcing phase and latex of both unvulcanized and prevulcanized natural rubber as the matrix. The chitin whiskers, prepared by acid hydrolysis of chitin from crab shell, consisted of slender parallelepiped rods with an aspect ratio close to 16. After the two aqueous suspensions were mixed and strirred, solid composite films were obtained either by freeze-drying and hot-pressing or by casting and evaporating the preparations. The processing and swelling behavior of composite films were evaluated. It was concluded that the whiskers form a rigid network assumed to be governed by a percolation mechanism in the evaporated samples only. Comparatively, better resistance of evaporated samples than hot-pressed ones against swelling in an organic solvent medium is good evidence for the existence of a rigid chitin network. The values of diffusion coefficient, bound rubber content, and relative weight loss also supported the presence of a three-dimensional chitin network within the evaporated samples. The mechanical behavior of the composites gives additional insight and evidence for this fact (part 2).

Enzymatic rearrangement of chitine hydrolysates with β-N-acetylhexosaminidase from Aspergillus oryzae

The role of higher chitooligomers in medical applications is increasing due to their interesting biological activities. Transglycosylation activity of β-N-acetylhexosaminidase from Aspergillus oryzae was employed to produce higher chitooligosaccharides (chitohexaose–chitooctaose) from a mixture of lower chitooligomers prepared by acid hydrolysis of chitin. Enzymatic rearrangement of the chitooligomer mixture was optimized in respect of substrate concentration, presence of inorganic salts, enzyme activity, and reaction time to achieve the highest production of longer chitooligomers.