Showing papers on "Chitin published in 2004"
TL;DR: A review of the literature on enzymes immobilized on chitin- and chitosan-based materials, covering the last decade, is presented in this paper, where one hundred fifty-eight papers on 63 immobilized enzymes for multiplicity of applications ranging from wine, sugar and fish industry, through organic compounds removal from wastewaters to sophisticated biosensors for both in situ measurements of environmental pollutants and metabolite control in artificial organs, are reviewed.
1,317 citations
Journal Article•
TL;DR: This study looks at the contemporary research in chitin and chitosan towards applications in various industrial and biomedical fields.
Abstract: Chitin and chitosan are considerably versatile and promising biomaterials. The deacetylated chitin derivative, chitosan is more useful and interesting bioactive polymer. Despite its biodegradability, it has many reactive amino side groups, which offer possibilities of chemical modifications, formation of a large variety of useful derivatives that are commercially available or can be made available via graft reactions and ionic interactions. This study looks at the contemporary research in chitin and chitosan towards applications in various industrial and biomedical fields.
1,153 citations
TL;DR: This work shows that ChiS, a sensor histidine kinase, regulates expression of the (GlcNAc)(2-6) gene set, and identifies three sets of differentially regulated genes that confer a significant growth advantage to V. cholerae on a chitin surface.
Abstract: Chitin, an insoluble polymer of GlcNAc, is an abundant source of carbon, nitrogen, and energy for marine microorganisms. Microarray expression profiling and mutational studies of Vibrio cholerae growing on a natural chitin surface, or with the soluble chitin oligosaccharides (GlcNAc)(2-6), GlcNAc, or the glucosamine dimer (GlcN)2 identified three sets of differentially regulated genes. We show that (i) ChiS, a sensor histidine kinase, regulates expression of the (GlcNAc)(2-6) gene set, including a (GlcNAc)2 catabolic operon, two extracellular chitinases, a chitoporin, and a PilA-containing type IV pilus, designated ChiRP (chitin-regulated pilus) that confers a significant growth advantage to V. cholerae on a chitin surface; (ii) GlcNAc causes the coordinate expression of genes involved with chitin chemotaxis and adherence and with the transport and assimilation of GlcNAc; (iii) (GlcN)2 induces genes required for the transport and catabolism of nonacetylated chitin residues; and (iv) the constitutively expressed MSHA pilus facilitates adhesion to the chitin surface independent of surface chemistry. Collectively, these results provide a global portrait of a complex, multistage V. cholerae program for the efficient utilization of chitin.
522 citations
TL;DR: In this paper, an electrospinning method was used to fabricate chitin nanofibous matrix for wound dressings, which was depolymerized by gamma irradiation to improve its solubility.
438 citations
TL;DR: The results indicate that the strong interactions between fillers and between the filler and SPI matrix play an important role in reinforcing the composites without interfering with their biodegradability.
329 citations
TL;DR: New environment-friendly beads prepared by a simple produce process for removal and recovery of heavy metals are developed based on mainly complexation adsorption model as well as a affinity of hydroxyl groups of the materials on metals.
302 citations
TL;DR: In this paper, the degree of substitution (DS) is an important parameter when assessing the conversion of chitin into one of its derivates, and FT-IR spectroscopy is a relatively easy but indirect way of determining the DS.
244 citations
TL;DR: A bacterial two-component hybrid sensor/kinase (of the ArcB type) that rigorously controls expression of approximately 50 genes, many involved in chitin degradation is described.
Abstract: Chitin, a highly insoluble polymer of GlcNAc, is produced in massive quantities in the marine environment. Fortunately for survival of aquatic ecosystems, chitin is rapidly catabolized by marine bacteria. Here we describe a bacterial two-component hybrid sensor/kinase (of the ArcB type) that rigorously controls expression of ≈50 genes, many involved in chitin degradation. The sensor gene, chiS, was identified in Vibrio furnissii and Vibrio cholerae (predicted amino acid sequences, full-length: 84% identical, 93% similar). Mutants of chiS grew normally on GlcNAc but did not express extracellular chitinase, a specific chitoporin, or β-hexosaminidases, nor did they exhibit chemotaxis, transport, or growth on chitin oligosaccharides such as (GlcNAc)2. Expression of these systems requires three components: wild-type chiS; a periplasmic high-affinity chitin oligosaccharide, (GlcNAc)n (n > 1), binding protein (CBP); and the environmental signal, (GlcNAc)n. Our data are consistent with the following model. In the uninduced state, CBP binds to the periplasmic domain of ChiS and “locks” it into the minus conformation. The environmental signal, (GlcNAc)n, dissociates the complex by binding to CBP, releasing ChiS, yielding the plus phenotype (expression of chitinolytic genes). In V. cholerae, a cluster of 10 contiguous genes (VC0620–VC0611) apparently comprise a (GlcNAc)2 catabolic operon. CBP is encoded by the first, VC0620, whereas VC0619–VC0616 encode a (GlcNAc)2 ABC-type permease. Regulation of chiS requires expression of CBP but not (GlcNAc)2 transport. (GlcNAc)n is suggested to be essential for signaling these cells that chitin is in the microenvironment.
226 citations
TL;DR: D dye/chitosan interaction showed favorable enthalpic and entropic processes, reflecting thermodynamic stability of the formed complex, while dye/ chitin interaction showed an exothermicEnthalpic value and a highly nonfavorable entropics effect, resulting in a nonspontaneous thermodynamic system.
176 citations
TL;DR: Cooperativity and the three-dimensional structure of beta-D-glucans indicate that weak noncovalent bonds are involved in the complex-forming mechanisms associated with zearalenone, which is more of an adsorption type than a binding type.
148 citations
TL;DR: Monitoring of mRNA levels and kinase activity of two MAPK genes and transcription factors suggest that AtMPK6/AtMPK3 and WRKY transcription factors (such as WRKY33 andWRKY53) may be important components of a pathway involved in chitin signalling in Arabidopsis plants.
Abstract: SUMMARY Chitin, a polysaccharide composed of beta-1-->4-linked N-acetyl-d-glucosamine, has been shown or implicated as a signal in plant defence and development. However, the key components of chitin perception and downstream signalling in non-leguminous plants are largely unknown. In recent years, mitogen-activated protein kinases (MAPKs) and their cascades were shown to transduce various extracellular stimuli into internal cellular responses. To investigate the possible involvement of MAPKs in chitin signalling in plants, the model plant Arabidopsis thaliana was treated with crab-shell chitin and also with the purified chitin oligomers (degree of polymerization, d.p. = 2-8). Both mRNA levels and kinase activity of two MAPK genes, AtMPK6 and AtMPK3, were monitored after treatment. The mRNA of AtMPK3 was strongly up-regulated by both chitin and its larger oligomers (d.p. = 6-8), but the mRNA of AtMPK6 did not appear to be regulated by these treatments. However, the kinase activity of both MAPKs was induced by chitin and the larger oligomers (d.p. = 6-8), with AtMPK6 much more strongly induced. In addition, WRKY22, WRKY29, WRKY33 and WRKY53, which encode four WRKY transcription factors that recognize TTGAC(C/T) W-box elements in promoters of numerous plant defence-related genes, were up-regulated by these treatments. WRKY33 and WRKY53 expression was induced by the transgenic expression of the tobacco MAPKK NtMEK2 active mutant NtMEK2(DD), suggesting a potential role for these WRKY transcription factors in relaying the signal generated from the MAPK cascade to downstream genes. These data suggest that AtMPK6/AtMPK3 and WRKY transcription factors (such as WRKY33 and WRKY53) may be important components of a pathway involved in chitin signalling in Arabidopsis plants.
TL;DR: The results suggested that the 1:4 chitin-PAA has a potential to be used as a wound dressing and possessed optimal physical properties.
TL;DR: A simple and sensitive method based on the use of colloidal chitin stained with Remazol Brilliant Blue R® (RBB) is proposed to evaluate chit inase activity to allow the selection or the comparison of chitinolytic microorganisms.
TL;DR: It is shown that Aspergillus niger also responds to cell wall stress by increasing chitin levels, and observations suggest thatcell wall stress in fungi may generally lead to activation of the chit in biosynthetic pathway.
Abstract: Perturbation of cell wall synthesis in Saccharomyces cerevisiae, either by mutations in cell wall synthesis-related genes or by adding compounds that interfere with normal cell wall assembly, triggers a compensatory response to ensure cell wall integrity. This response includes an increase in chitin levels in the cell wall. Here it is shown that Aspergillus niger also responds to cell wall stress by increasing chitin levels. The increased chitin level in the cell wall was accompanied by increased transcription of gfaA, encoding the glutamine: fructose-6-phosphate amidotransferase enzyme, which is responsible for the first and a rate-limiting step in chitin synthesis. Cloning and disruption of the gfaA gene in A. niger showed that it was an essential gene, but that addition of glucosamine to the growth medium could rescue the deletion strain. When the plant-pathogenic fungus Fusarium oxysporum and food spoilage fungus Penicillium chrysogenum were subjected to cell wall stress, the transcript level of their gfa gene increased as well. These observations suggest that cell wall stress in fungi may generally lead to activation of the chitin biosynthetic pathway. © 2004 SGM.
TL;DR: In this article, the average fiber diameter (310 nm) of poly(lactic-co-glycolic acid) (PLGA) and chitin in 1,1, 1,3, 3,3-hexafluoro-2-propanol (HFIP) and formic acid, respectively, was investigated to fabricate a biodegradable nanostructured composite matrix for tissue engineering.
TL;DR: Chitin deacetylase was important in initiating pathogenesis of M. anisopliae softening the insect cuticle to aid mycelial penetration and may have a dual role in modifying the Insect cuticular chitin for easy penetration as well as for altering its own cell walls for defense from insect chit inase.
TL;DR: In this paper, the chitin and its chitosan from the pens of Loligo lessoniana and Loligo formosana has been isolated, prepared, and physico-chemically characterized to demonstrate a potential Chitin source.
TL;DR: Chitin and chitosan were extracted from mycelial biomass of Cunninghamella elegans and the performance for copper, lead and iron biosorption in aqueous solution was evaluated.
TL;DR: Compared to chitosan, chitin at the higher concentration was found to induce stable collagen synthesis in the early wound healing process.
Abstract: Collagen synthesis was evaluated by measuring prolyl hydroxylase (PHL) activity induced within rat granulation tissue by a polyester non-woven fabric (NWF, 1 x 1 cm, 0.6 mm in thickness) impregnated with a chitin or chitosan suspension ranging in concentration from 0.1 to 10 mg/ml. In addition, PHL activity induced in rat granulation tissue by a NWF impregnated with a phosphate buffer solution was examined as a control. The PHL activity in each group remained low until 4 days post-implantation (Day 4). However, in the 10 mg chitin group, the PHL activity increased rapidly without scatter of the data at Day 7 and remained at a plateau until Day 14. In other groups, PHL activity increased linearly until Day 14. The data varied widely at Day 7. Compared to chitosan, chitin at the higher concentration was found to induce stable collagen synthesis in the early wound healing process.
TL;DR: The Mark-Houwink-Sakurada equation and the relationship between the z-average radius of gyration (Rg) and the weight-average molecular weight (Mw) were determined to be [eta] = 0.10Mw0.68 (mL), suggesting a random-coil structure for the chitin molecules in alkali conditions.
01 Jan 2004
TL;DR: Analysis of the binding activity using deletion mutants of BMCPs revealed that this type of conserved region also functions as the chitin-binding domain, similarly to the RR-2 region previously shown to confer chitIn binding, and the extended R&R consensus is the general chit in-bindingdomain of cuticle proteins in Arthropoda.
TL;DR: Hybrid scaffolds composed of beta-chitin and collagen were prepared by combining salt-leaching and freeze-drying methods and showed a good affinity to and proliferation on all collagen-coated chitins.
TL;DR: This procedure includes deproteinization of bee corpses, discoloration of the chitin–melanin complex, deacetylation, and enzymatic hydrolysis of chitosan.
Abstract: The procedure of isolation of chitin, chitosan, and water-soluble low-molecular-weight chitin from the corpses of bees was developed. This procedure included deproteinization of the corpses of bees, discoloration of the chitin-melanin complex, deacetylation, and enzymatic hydrolysis of chitosan.
TL;DR: A unique chitin catabolic pathway in T. kodakaraensis is revealed, in which GlcNAc2 produced from chit in is degraded by the concerted action of Tk-Dac and Tk -GlmA, and a novel mechanism for dimer processing using a combination of deacetylation and cleavage is defined.
TL;DR: In this article, the regenerated chitin with DNAc degree of 87% and N -acetylated Chitosan degree of 93% were used as starting materials to obtain β-1,4-linked poly-N-acetylglucosaminuronic acid (chitouronic acid) Na salts.
TL;DR: Chitin was functionalized with hexamethylenediamine followed by glutaraldehyde activation, and its capacity to bind Candida rugosa lipase was investigated, resulting in a uniform enzyme fixation with high catalytic activity.
TL;DR: It is found that in CBP1 and CBP2, potential trypsin and chymotrypsin cleavage sites reside primarily within the chitin binding domain sequences, limiting exposure of the potential cleavage Sites to the digestive proteinases.
TL;DR: It appeared that chitin synthesis and hydrolysis were not coupled, but that both were regulated during yeast-hypha morphogenesis in C. albicans.
Abstract: Chitin is an essential structural polysaccharide in fungi that is required for cell shape and morphogenesis. One model for wall synthesis at the growing cell surface suggests that the compliance that is necessary for turgor-driven expansion of the cell wall involves a delicate balance of wall synthesis and lysis. Accordingly, de novo chitin synthesis may involve coordinated regulation of members of the CHS chitin synthase and CHT chitinase gene families. To test this hypothesis, the chitin synthase and chitinase activities of cell-free extracts were measured, as well as the chitin content of cell walls isolated from isogenic mutant strains that contained single or multiple knock-outs in members of these two gene families, in both Candida albicans and Saccharomyces cerevisiae. However, deletion of chitinase genes did not markedly affect specific chitin synthase activity, and deletion of single CHS genes had little effect on in vitro specific chitinase activity in either fungus. Chitin synthesis and chitinase production was, however, regulated in C. albicans during yeast-hypha morphogenesis. In C. albicans, the total specific activities of both chitin synthase and chitinase were higher in the hyphal form, which was attributable mainly to the activities of Chs2 and Cht3, respectively. It appeared, therefore, that chitin synthesis and hydrolysis were not coupled, but that both were regulated during yeast-hypha morphogenesis in C. albicans.
TL;DR: The chitin synthase mutants constructed through targeted gene disruption by homologous recombination will be useful for elucidating cell wall biogenesis in F. oxysporum and the relationship between fungal cell wall integrity and pathogenicity.
Abstract: Three structural chitin synthase genes, chs1, chs2 and chs3, were identified in the genome of Fusarium oxysporum f. sp. lycopersici, a soilborne pathogen causing vascular wilt disease in tomato plants. Based on amino acid identities with related fungal species, chs1, chs2 and chs3 encode structural chitin synthases (CSs) of class I, class II and class III, respectively. A gene (chs7) encoding a chaperone-like protein was identified by comparison of the deduced protein with Chs7p from Saccharomyces cerevisiae, an endoplasmic reticulum (ER) protein required for the export of ScChs3p (class IV) from the ER. So far no CS gene belonging to class IV has been isolated from F. oxysporum, although it probably contains more than one gene of this class, based on the genome data of the closely related species Fusarium graminearum. F. oxysporum chs1-, chs2- and chs7-deficient mutants were constructed through targeted gene disruption by homologous recombination. No compensatory mechanism seems to exist between the CS genes studied, since chitin content determination and expression analysis of the chs genes showed no differences between the disruption mutants and the wild-type strain. By fluorescence microscopy using Calcofluor white and DAPI staining, the wild-type strain and Δchs2 and Δchs7 mutants showed similar septation and even nuclear distribution, with each hyphal compartment containing only one nucleus, whereas the Δchs1 mutant showed compartments containing up to four nuclei. Pathogenicity assays on tomato plants indicated reduced virulence of Δchs2 and Δchs7 null mutants. Stress conditions affected normal development in Δchs2 but not in Δchs1 or Δchs7 disruptants, and the three chs-deficient mutants showed increased hyphal hydrophobicity compared to the wild-type strain when grown in sorbitol-containing medium. The chitin synthase mutants will be useful for elucidating cell wall biogenesis in F. oxysporum and the relationship between fungal cell wall integrity and pathogenicity.