Showing papers on "Chitin published in 1984"

Use of chitinous polymers in food: A challenge for food research and development

Abstract: The processing, safety and nutritional aspects, and functional properties (hydrophilic, interphasic, intermolecular, sensory) of chitin and chitosan are described in a detailed literature review. Their biomass recovery, their use for removing undesirable trace elements, dyes, and acidic components, and their applications as biodegradable carriers for food additives also are discussed. Numerous food applications for chitin (a mycopolysaccharide conjugated with protein) and chitosan (deacetylated chitin) can be identified for these waste products as coagulating and complexing agents. (wz)

Effect of Chitosan, Chitin and some Aminosugars on Growth of Various Soilborne Phytopathogenic Fungi

Abstract: The effect of bleached chitin, 66% and 91% deacetylated chitosan, respectively, as well as some aminosugars on in vitro radial growth of several phytopathogenic oomycetes and deuteromycets was studied In contrast to chitin, chitosan was inhibitory to the fungi The antifungal activity depended on the degree of deacetylation, the particle diameter of the polymer, the growth medium and the pH. Likewise, deacetylation of the monomers different media varied, indicating a possible counteraction by the carbohydrate sources. Zusammenfassung Der Einflus von Chitosan, Chitin und einigen Aminozuckern auf das Wachstum von verschiedenen bodenburtigen phytopathogenen Pilzen Die Wirkung von Chitin, 66% und 91% deacetyliertem Chitosan sowie einigen Aminozuckern auf das Wachstum in vitro einiger phytopathogener Oomyceten und Deutero-myceten wurde untersucht. Im Gegensatz zu Chitin wurde das Wachstum der Pilze durch und der Grose der Chitosanpartikeln, dem Medium und dem pH abhangig. Deacetylierung der Monomeren fuhrte ebenfalls zu einer erhohten antifungischen Aktivitat. Die Wirkung des Glucosamins auf das Pilzwachstum drei verschiedenen Medien variierte, was auf eine mogliche Gegenwirkung der Kohlenhydrate der Medien hinweist.

Protecting Effect of Chitin and Chitosan on Experimentally Induced Murine Candidiasis

Abstract: Chitin and chitosan were found to exhibit a protective effect on mice administered these polysaccharides intraperitoneally against infection of the viable cells of Candida albicans NIH A-207 strain. A significant difference was observed between the protective effects of chitin and chitosan, i.e., chitin was much more effective than chitosan when the C. albicans cells were challenged via the intravenous route. In intraperitoneal inoculations of C. albicans cells, however, chitosan provided stronger resistance for mice than chitin. It has also been revealed that the number of polymorphonuclear leukocytes from circulating blood of chitin-administered mice increased remarkably compared with that of untreated and chitosan-treated mice, and that the increase of active oxygen-generating phagocytic cells was significant. On the other hand, the number of peritoneal exudate cells (PEC) and the amounts of active oxygen generated from these cells in chitosan-treated mice were larger than those of chitin-treated mice. However, candidacidal activities of PEC per fixed cell number in mice treated with chitin or with chitosan were almost the same and greater than those of untreated mice.

Proteinase Inhibitor Synthesis in Tomato Leaves Induction by Chitosan Oligomers and Chemically Modified Chitosan and Chitin

Abstract: Soluble chemical derivatives of chitin and chitosan including ethylene glycol chitin, nitrous acid-modified chitosan, glycol chitosan, and chitosan oligomers, produced from chitosan by limited hydrolysis with HCl, were found to possess proteinase inhibitor inducing activities when supplied to young excised tomato (Lycopersicon esculentum var Bonnie Best) plants. Nitrous acid-modified chitosans and ethylene glycol chitin exhibited about 2 to 3 times the activity of acid hydrolyzed chitosan and 15 times more activity than glycol chitosan. The parent chitin and chitosans are insoluble in water or neutral buffers and cannot be assayed. Glucosamine and its oligomers from degree of polymerization = 2 through degree of polymerization = 6 were purified from acid-fragmented chitosan and assayed. The monomer was inactive and dimer and trimer exhibited weak activities. Tetramer possessed higher activity and the larger pentamer and hexamer oligomers were nearly as active as the total hydrolyzed mixture. None of the fragments exhibited more than 2% acetylation (the limits of detection). The contents of the acid-fragmented mixture of oligomers was chemically N-acetylated to levels of 13% and 20% and assayed. The N-acetylation neither inhibited nor enhanced the proteinase inhibitor inducing activity of the mixture. These results, along with recent findings by others that chitinases and chitosanases are present in plants, provide further evidence for a possible role of soluble chitosan fragments as signals to activate plant defense responses.

Application of chitin and chitosan to pharmaceutical preparations

Abstract: With a view towards application of chitin and chitosan in pharmaceutical preparations, investigations were done on directly compressed tablets containing chitin or chitosan, sustained-release preparations of water-soluble drugs with chitosan, and dissolution properties and bioavailability of poorly soluble drugs from ground mixtures with chitin or chitosan.

N,O-carboxymethyl chitosan and preparative method therefor

Abstract: A novel chitosan derivative, having carboxymethyl substituents on some of both the amino and primary hydroxyl sites of the glucosamine units of the chitosan structure, is disclosed, together with methods for its preparation starting from either chitosan or chitin

Chitosan, a natural regulator in plant-fungal pathogen interactions, increases crop yields

Abstract: Chitosan is a naturally occurring component in the cell walls of many plant pathogenic fungi. It has dual roles in the interaction between pea tissue and the formae speciales of the pathogenic fungus , Fusarium solani. First, it inhibits Fusarium spore germination and growth. Second, chitosan, when applied to pea tissue, induces protection against subsequent inoculations of a virulent pathogen. The biochemistry and gene regulation of this protection response induced by chitosan is indistinguishable from the cross protection induced by an incompatible Fusarium solani strain. Some of the genes activated in the resistance response have been isolated and cloned. Chitosan commercially derived from crab shell chitin has been tested as seed treatments and foliar applications to field crops. Some of the seed treatment applications resulted in cost effective increases in yield.

The co-ordination of chitosan and chitin synthesis in Mucor rouxii.

Abstract: Chitin synthetase preparations from cell walls and chitosomes of the fungus Mucor rouxii were tested for their ability to synthesize chitosan when incubated with uridine diphosphate N-acetyl-D-glucosamine in the presence of chitin deacetylase. The most effective chitin synthetase preparation was one dissociated from cell walls with digitonin. The rate of chitosan synthesis by the wall-dissociated chitin synthetase was about three times that of an equivalent amount of cell walls. The chitosan-synthesizing ability of chitosomes was relatively low, but was more than tripled by treatment with digitonin. Presumably, digitonin improves chitosan yields by dissociating chitin synthetase. The dissociated enzyme would produce dispersed chitin chains that could be attacked by chitin deacetylase before they have had time to crystallize into microfibrils. The regulation of chitin and chitosan syntheses in vivo may be determined by the organization of chitin synthetase molecules at the cell surface. Those molecules that remain organized as a complex, similar if not identical to that found in chitosomes, would produce mainly chitin. Chitosan would be preferentially produced by chitin synthetase molecules which are dispersed upon reaching the cell surface.

The detection and analysis of chitinase activity from the yeast form of Candida albicans.

Abstract: Chitinase activity was detected in the supernatant fraction of a high-speed centrifugation preparation of broken Candida albicans yeast cells. The enzyme showed peak activity during the rapid budding phase of growth and was found to parallel the chitin synthase activity. The optimum conditions for the hydrolysis of chitin, regenerated from acetylation of chitosan, were determined. Analysis of the kinetics of the enzyme-substrate interaction and a measurement of their binding suggests that an equilibrium binding situation exists and that the kinetics follow a Langmuir isotherm interaction.

Chitosomes from the wall-less "slime" mutant of Neurospora crassa

Abstract: Cell-free extracts from the wall-less slime mutant of Neurospora crassa and the mycelium of wild type exhibit similar chitin synthetase properties in specific activity, zymogenicity and a preferential intracellular localization of chitosomes. The yield of chitosomal chitin synthetase from sline cells was essentially the same irrespective of cell breakage procedure (osmotic lysis or ballistic disruption) —an indication that chitosomes are not fragments of larger membranes produced by harsh (ballistic) disruption procedures. The plasma membrane fraction, isolated from slime cells treated with concanavalin A, contained only a minute portion of the total chitin synthetase of the fungus. Most of the activity was in the cytoplasmic fraction; isopycnic sedimentation of this fraction on a sucrose gradient yielded a sharp band of chitosomes with a buoyant density=1.125 g/ cm3. Approximately 76% of the total chitin synthetase activity of the slime mutant was recovered in the chitosome band. Because of their low density, chitosomes could be cleanly separated from the rest of the membranous organelles of the fungus. Apparently, the lack of a cell wall in the slime mutant is not due to the absence of either chitosomes or zymogenic chitin synthetase.

Chitosanases: occurrence, production and immobilization

Abstract: Microbial soil populations were found to contain chitosan-degrading bacteria comprising 1-7% of the heterotrophic bacteria. The basis for this considerable component of the total microbial population is discussed. The production of chitosanase from one such lytic soil bacterium, Bacillus circulans, was optimized. The enzyme was efficiently purified through affinity chromatography and its general characteristics determined. The chitosanase was immobilized by a variety of methods, the best being via covalent binding to carbodiimidazole-activated agarose beads. The role of chito sanas es within the context of microbial mineralization of chitin and chitosan is discussed.

Inhibition of chitin metabolism by avermectin in susceptible organisms

Abstract: Avermectin inhibits Mucor miehei and Artemia salina chitin synthesis and to a degree DNA synthesis in the former. The antibiotic interferes with chitin turnover in brine shrimp and inhibits Streptomyces antibioticus chitinase activity in vitro. In light of the proposed mode of action of avermectin and the anomolies in the literature, it is proposed that avermectin can kill susceptible organisms not only by a neurotoxic mechanism but also by inhibiting chitin turnover and synthesis at low concentration and thus the molting/ecdysis process.

Chitinase-producing bacteria

Abstract: Novel bacteria strains are described which are created by the introduction of DNA encoding for the production of chitinase, an enzyme capable of degrading chitin present in fungi and nematodes The strains have utility in producing chitinase for the purpose of inhibiting plant pathogens

Localization of Chitin synthase in Mucor rouxii by an autoradiographic method.

Abstract: The localization of chitin synthase in the cells of Mucor rouxii was studied by a method which combined permeabilization of the cells with toluene/ethanol and incubation with the radioactive substrate UDP-[3H]GlcNAc followed by high resolution autoradiography. By this technique it was demonstrated that most of the chitin synthesized by these cells was located within the cytoplasm, and only a small amount of the enzyme product appeared at the cell surface. It was concluded that most of the chitin synthase of M. rouxii is located in the cytoplasm of the cells.

Partially deacetylated chitin: its use in self-regulated drug delivery systems

Abstract: Chitin, poly-β-(1→4) linked N-acetyl-D-glucosamine, is a highly hydrophobic material that is insoluble in water and most ordinary solvents. This property of chitin restricts its use to applications that do not require solubilization of the polymer. Several useful derivatives of chitin have been prepared that increase the hydrophilicity of the polymer. One of these derivatives is prepared by deacetylation of chitin's N-acetyl-glucosamine units in strong alkali. Deacetylated chitin is soluble in dilute acidic solutions and, in some cases, depending on the degree of deacetylation, in water. Although the maximally deacetylated material, chitosan, is not degraded by lysozyme, partially deacetylated chitin is a substrate for lysozyme digestion. Kinetic studies of the degradation reaction show that the hydrolysis of partially deacetylated chitin by lysozyme and a lysozyme-hapten conjugate follows typical Michaelis-Menten kinetics. Apparent K m values for the native and modified enzymes were 45 μg/ml and 40 μUg/ml, respectively. Dilute acidic solutions of partially deacetylated chitin were cast to form tough, flexible, water-insoluble films or crosslinked with glutaraldehyde to form hydrogels. Both of these fabrications were found to be lysozyme degradable. These data are discussed in relationship to the possible use of partially deacetylated chitin in bioerodible drug delivery systems.

The laminarinase system of Streptomyces sp., ATCC 11238

Abstract: Extracellular proteins from Streptomyces sp. ATCC 11238 grown on fungal mycelia and chitin as C- and N-sources were concentrated by ultrafiltration and acetone precipitation. The crude preparation containing chitin and laminarin degrading enzymes was fractionated by repeated gel filtrations. Three different types of β-1,3-glucanases were found. Besides oligomeric breakdown products laminaritriose is the main product of laminarin hydrolysis by one endo-β-1,3-glucanase. A second laminarin degrading (exo-splitting) enzyme yields predominantly laminaribiose. Another exo-β-1,3-glucanase liberates glucose but no, oligosaccharides from the nonreducing end of laminarin.