Preparative methods of phosphorylated chitin and chitosan--an overview

Biomaterials such as chitin, chitosan and their derivatives have a significant and rapid development in recent years. Chitin and chitosan have become cynosure of all party because of an unusual combination of biological activities plus mechanical and physical properties. However, the applications of chitin and chitosan are limited due to its insolubility in most of the solvents. The chemical modification of chitin and chitosan are keen interest because of these modifications would not change the fundamental skeleton of chitin and chitosan but would keep the original physicochemical and biochemical properties. They would also bring new or improved properties. The chemical modification of chitin and chitosan by phosphorylation is expected to be biocompatible and is able to promote tissue regeneration. In view of rapidly growing interest in chitin and chitosan and their chemical modified derivatives, we are here focusing the recent developments on preparation of phosphorylated chitin and chitosan in different methods.     

Novel chitin and chitosan nanofibers in biomedical applications

Chitin and its deacetylated derivative, chitosan, are non-toxic, antibacterial, biodegradable and biocompatible biopolymers. Due to these properties, they are widely used for biomedical applications such as tissue engineering scaffolds, drug delivery, wound dressings, separation membranes and antibacterial coatings, stent coatings, and sensors. In the recent years, electrospinning has been found to be a novel technique to produce chitin and chitosan nanofibers. These nanofibers find novel applications in biomedical fields due to their high surface area and porosity. This article reviews the recent reports on the preparation, properties and biomedical applications of chitin and chitosan based nanofibers in detail.     

Chitosan derivatives obtained by chemical modifications for biomedical and environmental applications

Chitosan is a natural based polymer, obtained by alkaline deacetylation of chitin, which presents excellent biological properties such as biodegradability and immunological, antibacterial and wound-healing activity. Recently, there has been a growing interest in the chemical modification of chitosan in order to improve its solubility and widen its applications. The main chemical modifications of chitosan that have been proposed in the literature are reviewed in this paper. Moreover, these chemical modifications lead to a wide range of derivatives with a broad range of applications. Recent and relevant examples of the distinct applications, with particular emphasis on tissue engineering, drug delivery and environmental applications, are presented.     

Recent trends in biological extraction of chitin from marine shell wastes: a review

The natural biopolymer chitin and its deacetylated product chitosan are widely used in innumerable applications ranging from biomedicine, pharmaceuticals, food, agriculture and personal care products to environmental sector. The abundant and renewable marine processing wastes are commercially exploited for the extraction of chitin. However, the traditional chitin extraction processes employ harsh chemicals at elevated temperatures for a prolonged time which can harm its physico-chemical properties and are also held responsible for the deterioration of environmental health. In view of this, green extraction methods are increasingly gaining popularity due to their environmentally friendly nature. The bioextraction of chitin from crustacean shell wastes has been increasingly researched at the laboratory scale. However, the bioextraction of chitin is not currently exploited to its maximum potential on the commercial level. Bioextraction of chitin is emerging as a green, cleaner, eco-friendly and economical process. Specifically in the chitin extraction, microorganisms-mediated fermentation processes are highly desirable due to easy handling, simplicity, rapidity, controllability through optimization of process parameters, ambient temperature and negligible solvent consumption, thus reducing environmental impact and costs. Although, chitin production from crustacean shell waste through biological means is still at its early stage of development, it is undergoing rapid progress in recent years and showing a promising prospect. Driven by reduced energy, wastewater or solvent, advances in biological extraction of chitin along with valuable by-products will have high economic and environmental impact.     

Sulfated chitin and chitosan as novel biomaterials

Chitin and chitosan are known to be natural polymers and they are non-toxic, biodegradable and biocompatible. Chemical modification of chitin and chitosan with sulfate to generate new bifunctional materials is of interest because the modification would not change the fundamental skeleton of chitin and chitosan, would keep the original physicochemical and biochemical properties and finally would bring new or improved properties. The sulfated chitin and chitosan have a variety of applications, such as, adsorbing metal ions, drug delivery systems, blood compatibility, and antibacterial field. The purpose of this review is to take a closer look about the different synthetic methods and potential applications of sulfated chitin and chitosan. Based on current research and existing products, some new and futuristic approaches in this context area are discussed in detail. From the studies reviewed, we concluded that sulfated chitin and chitosan are promising materials for biomedical applications.     

Implications of molecular diversity of chitin and its derivatives

Chitin is a long unbranched polysaccharide, made up of β-1,4-linked N-acetylglucosamine which forms crystalline fiber-like structure. It is present in the fungal cell walls, insect and crustacean cuticles, nematode eggshells, and protozoa cyst. We provide a critical appraisal on the chemical modifications of chitin and its derivatives in the context of their improved efficacy in medical applications without any side effect. Recent advancement in nanobiotechnology has helped to synthesize several chitin derivatives having significant biological applications. Here, we discuss the molecular diversity of chitin and its applications in enzyme immobilization, wound healing, packaging material, controlled drug release, biomedical imaging, gene therapy, agriculture, biosensor, and cosmetics. Also, we highlighted chitin and its derivatives as an antioxidant, antimicrobial agent, anticoagulant material, food additive, and hypocholesterolemic agent. We envisage that chitin and chitosan-based nanomaterials with their potential applications would augment nanobiotechnology and biomedical industries.

     

Preparation of chitin nanofibril/polycaprolactone nanocomposite from a nonaqueous medium suspension

Chitin nanofibrils are prepared by treatment of commercial chitin in hydrochloric acid. It is found for the first time that the obtained chitin nanofibrils can be well dispersed in an organic solvent of 2,2,2-trifluoroethanol (TFE) due to its strong ability to form hydrogen bonds. Polycaprolactone (PCL), a water insoluble biodegradable polymer, is selected to blend with chitin nanofibrils to achieve chitin nanofibril/polycaprolactone (n-chitin/PCL) nanocomposites using TFE as a co-solvent. The results show the n-chitin/PCL nanocomposites, either in the form of solvent-cast films or electrospun fiber mats, both exhibit reinforced mechanical properties. Thus, the processing technique from a TFE suspension instead of aqueous suspensions is a good alternative to broaden the family of chitin nanofibril-based nanocomposites.     

Chitin deacetylases: new, versatile tools in biotechnology

Chitin deacetylases have been identified in several fungi and insects. They catalyse the hydrolysis of N-acetamido bonds of chitin, converting it to chitosan. Chitosans, which are produced by a harsh thermochemical procedure, have several applications in areas such as biomedicine, food ingredients, cosmetics and pharmaceuticals. The use of chitin deacetylases for the conversion of chitin to chitosan, in contrast to the presently used chemical procedure, offers the possibility of a controlled, non-degradable process, resulting in the production of novel, well-defined chitosan oligomers and polymers.     

Serratia marcescens chitinase: One-step purification and use for the determination of chitin

The extracellular chitinase produced by Serratia marcescens was obtained in highly purified form by adsorption-digestion on chitin. After gel electrophoresis in a nondenaturing system, the purified preparation exhibited two major protein bands that coincided with enzymatic activity. A study of the enzyme properties showed its suitability for the analysis of chitin. Thus, the chitinase exhibited excellent stability, a wide pH optimum, and linear kinetics over a much greater range than similar enzymes from other sources. The major product of chitin hydrolysis was chitobiose, which was slowly converted into free N-acetylglucosamine by traces of β-N-acetylglucosaminidase present in the purified preparation. The preparation was free from other polysaccharide hydrolases. Experiments with radiolabeled yeast cell walls showed that the chitinase was able to degrade wall chitin completely and specifically.     

Preparation of biodegradable chitin/gelatin membranes with GlcNAc for tissue engineering applications

Chitin is a natural biopolymer have been used for several biomedical applications due to its biodegradability and biocompatibility. By using the calcium solvent system, chitin regenerated hydrogel (RG) was prepared by using -chitin. And also, the swelling hydrogel (SG) was prepared by using β-chitin with water. Then, both RG and SG were mixed with gelatin and N-acetyl-d-(+)-glucosamine (GlcNAc) at 120 °C for 2 h. The chitin/gelatin membranes with GlcNAc were also prepared by using RG and SG with GlcNAc. The prepared chitin/gelatin membranes with or without GlcNAc were characterized by mechanical, swelling, enzymatic degradation, thermal and growth of NIH/3T3 fibroblast cell studies. The stress and elongation of chitin/gelatin membrane with GlcNAc prepared from RG was showed higher than the chitin/gelatin membranes without GlcNAc. But, the chitin/gelatin membranes prepared from SG with GlcNAc was showed higher stress and elongation than the chitin/gelatin membranes without GlcNAc. It is due to the crosslinking effect of GlcNAc. The chitin/gelatin membranes prepared from SG showed higher swelling than the chitin/gelatin membranes prepared from RG. In contrast, the chitin/gelatin membranes prepared from RG showed higher degradation than the chitin/gelatin membranes prepared from SG. And also, these chitin/gelatin membranes are showing good growth of NIH/3T3 fibroblast cell. So these novel chitin/gelatin membranes are useful for tissue engineering applications.     

GENDER INFLUENCES DIFFERENTIATION OF CHITIN AMONG BODY PARTS

Earlier reports have established that chitin isolates from each body part of an insect cuticle can exhibit diverse physicochemical properties. But it is still unknown if the gender of the insect can influence characteristics of chitin isolates from different body parts. The present study addresses this question. As a result, important physicochemical differences in the chitin samples from different body parts of Melolontha sp. were recorded on the basis of sex. The chitin samples were extracted from eight different body parts (antennae, head, eyes, thorax, abdomen, elytra, hindwings, and legs) of female and male. The most remarkable variations in the chitin isolates from female and male body parts were recorded in chitin content, crystallinity, thermal stability, and surface morphology. And also it was wondered these chitin isolates from different body parts of female and male could find different applications. To check this hypothesis, the chitin samples from female and male were interacted with bovine serum albumin (BSA) protein and important variations were observed.     

Chitin whiskers: an overview

Chitin is the second most abundant semicrystalline polysaccharide. Like cellulose, the amorphous domains of chitin can also be removed under certain conditions such as acidolysis to give rise to crystallites in nanoscale, which are the so-called chitin nanocrystals or chitin whiskers (CHWs). CHW together with other organic nanoparticles such as cellulose whisker (CW) and starch nanocrystal show many advantages over traditional inorganic nanoparticles such as easy availability, nontoxicity, biodegradability, low density, and easy modification. They have been widely used as substitutes for inorganic nanoparticles in reinforcing polymer nanocomposites. The research and development of CHW related areas are much slower than those of CW. However, CHWs are still of strategic importance in the resource scarcity periods because of their abundant availability and special properties. During the past decade, increasing studies have been done on preparation of CHWs and their application in reinforcing polymer nanocomposites. Some other applications such as being used as feedstock to prepare chitosan nanoscaffolds have also been investigated. This Article is to review the recent development on CHW related studies.     

Bacterial chitinases: properties and potential

Chitin is among the most abundant biomass present on Earth. Chitinase plays an important role in the decomposition of chitin and potentially in the utilization of chitin as a renewable resource. During the previous decade, chitinases have received increased attention because of their wide range of applications. Chito-oligomers produced by enzymatic hydrolysis of chitin have been of interest in recent years due to their broad applications in medical, agricultural, and industrial applications, including antibacterial, antifungal, hypocholesterolemic, and antihypertensive activity, and as a food quality enhancer. Microorganisms, particularly bacteria, form one of the major sources of chitinase. In this article, we have reviewed some of the chitinases produced by bacterial systems that have gained worldwide research interest for their diverse properties and potential industrial uses.     

壳聚糖酶结构与功能的研究进展

壳聚糖酶是一类对壳聚糖具有较高催化活性而几乎不水解几丁质的糖苷水解酶,其可将高分子量的壳聚糖转化为低分子量的功能性壳寡糖。近年来,对壳聚糖酶的相关研究取得了显著进展,因此,本文对其生化性质、晶体结构、催化机制和蛋白质工程改造进行总结和探讨,并对酶法制备壳寡糖纯品进行展望,这将加深研究者对壳聚糖酶作用机制的认识,推动壳聚糖酶的工业应用。     

Chitin deacetylase product inhibition

Chitin deacetylase is the only known enzyme catalyzing the hydrolysis of the acetamino linkage in the N-acetylglucosamine units of chitin and chitosan. This reaction can play an important role in enzymatic production of chitosan from chitin, or in enzymatic modification of chitosan, which has applications in medicine, pharmacy or plant protection. It was previously shown that acetic acid, a product of the deacetylation process, may act as an inhibitor of chitin deacetylase. Here we show the mechanism of inhibition of chitin deacetylase isolated from Absidia orchidis vel coerulea by acetic acid released during the deacetylation process. The process follows competitive inhibition with respect to acetic acid with an inhibition constant of K(i) = 0.286 mmol/L. These results will help to find the optimal system to carry out the enzymatic deacetylation process for industrial applications.     

Macroporous chitin affinity membranes for lysozyme separation

Macroporous chitin membranes with high, controlled porosity and good mechanical properties have been prepared using a technique developed in this laboratory based on silica particles as porogen. They were employed for the affinity separation of lysozyme. Chitin membranes (1 mm thickness) can be operated at high fluxes (>/=1.1 mL/min/cm(2)) corresponding to pressure drops >/=2 psi. Their adsorption capacity for lysozyme ( approximately 50 mg/mL membrane) is by an order of magnitude higher than that of the chitin beads employed in column separation. In a binary mixture of lysozyme and ovalbumin, the membranes showed very high selectivity towards lysozyme. The effect of some important operation parameters, such as the flow rates during loading and elution were investigated. Lysozyme of very high purity (>98%) was obtained from a mixture of lysozyme and ovalbumin, and from egg white. The results indicate that the macroporous chitin membranes can be used for the separation, purification, and recovery of lysozyme at large scale. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 610-617, 1997.     

Extraction and characterization of chitin and chitosan from marine sources in Arabian Gulf

Chitin in the α and the β forms has been extracted from different marine crustacean from the Arabian Gulf. The contents of the various exoskeletons have been analyzed and the percent of the inorganic salt (including the various elements present), protein and the chitin was determined. Deacetylation of the different chitin produced was conducted by the conventional thermal heating and by microwave heating methods. Microwave heating has reduced enormously the time of heating from 6–10 h to 10–15 min, to yield the same degree of deacetylation and higher molecular weight chitosan. This technique can save massive amount of energy when implemented on a semi-industrial or industrial scale. The chitin and the obtained chitosan were characterized by elemental analysis, XRD, NMR, FTIR and thermogravimetric measurements. XRD analysis showed that chitosan has lower crystallinity than its corresponding chitin; meanwhile its thermal stability is also lower than chitin.     

Chitosan functional properties

Chitosan is a partially deacetylated polymer of N-acetyl glucosamine. It is essentially a natural, water-soluble, derivative of cellulose with unique properties. Chitosan is usually prepared from chitin (2 acetamido-2-deoxy β-1,4-D-glucan) and chitin has been found in a wide range of natural sources (crustaceans, fungi, insects, annelids, molluscs, coelenterata etc.) However chitosan is only manufactured from crustaceans (crab and crayfish) primarily because a large amount of the crustacean exoskeleton is available as a by product of food processing. Squid pens (a waste byproduct of New Zealand squid processing) are a novel, renewable source of chitin and chitosan. Squid pens are currently regarded as waste and so the raw material is relatively cheap. This study was intended to assess the functional properties of squid pen chitosan. Chitosan was extracted from squid pens and assessed for composition, rheology, flocculation, film formation and antimicrobial properties. Crustacean chitosans were also assessed for comparison. Squid chitosan was colourless, had a low ash content and had significantly improved thickening and suspending properties. The flocculation capacity of squid chitosan was low in comparison with the crustacean sourced chitosans. However it should be possible to increase the flocculation capacity of squid pen chitosan by decreasing the degree of acetylation. Films made with squid chitosan were more elastic than crustacean chitosan with improved functional properties. This high quality chitosan could prove particularly suitable for medical/analytical applications. This revised version was published online in November 2006 with corrections to the Cover Date.     

Bacterial Chitinases: Properties and Potential

ABSTRACT

Chitin is among the most abundant biomass present on Earth. Chitinase plays an important role in the decomposition of chitin and potentially in the utilization of chitin as a renewable resource. During the previous decade, chitinases have received increased attention because of their wide range of applications. Chito-oligomers produced by enzymatic hydrolysis of chitin have been of interest in recent years due to their broad applications in medical, agricultural, and industrial applications, including antibacterial, antifungal, hypocholesterolemic, and antihypertensive activity, and as a food quality enhancer. Microorganisms, particularly bacteria, form one of the major sources of chitinase. In this article, we have reviewed some of the chitinases produced by bacterial systems that have gained worldwide research interest for their diverse properties and potential industrial uses.     

Preparation and Characterization of a Novel Co-processed Excipient of Chitin and Crystalline Mannitol

A co-processed excipient was prepared from commercially available crystalline mannitol and α-chitin using direct compression as well as spray, wet, and dry granulation. The effect of the ratio of the two components, percentage of lubricant and particle size, on the properties of the prepared co-processed excipient has been investigated. α-Chitin forms non-hygroscopic, highly compactable, disintegrable compacts when co-processed with crystalline mannitol. The compaction properties of the co-processed mannitol–chitin mixture were found to be dependent upon the quantity of mannitol added to chitin, in addition to the granulation procedure used. Optimal physicochemical properties of the excipient, from a manufacturing perspective, were obtained using a co-processed mannitol–chitin (2:8, w/w) mixture prepared by wet granulation (Cop-MC). Disintegration time, crushing strength, and friability of tablets, produced from Cop-MC using magnesium stearate as a lubricant, were found to be independent of the particle size of the prepared granules. The inherent binding and disintegration properties of the compressed Cop-MC are useful for the formulation of poorly compressible, high-strength, and low-strength active pharmaceutical ingredients. The ability to co-process α-chitin with crystalline mannitol allows chitin to be used as a valuable industrial pharmaceutical excipient.