Chitin

About: Chitin is a research topic. Over the lifetime, 6590 publications have been published within this topic receiving 253993 citations.

Binding and substrate specificities of a Streptomyces olivaceoviridis chitinase in comparison with its proteolytically processed form.

Abstract: Streptomyces olivaceoviridis is an efficient chitin degrader. One of its genes encoding an exochitinase (exo-ChiO1) was previously characterized. The transcription was found to be inducible by chitin, but not by glucose. The transcriptional start site is situated 38 bp upstream of the start codon. S. olivaceoviridis as well as transformants of S. vinaceus and S. lividans carrying the exo-chiO1 gene on a multicopy vector secrete a 59-kDa chitinase which adheres strongly and under most conditions irreversibly to the substrate chitin. After having released the enzyme from the crystalline substrate in the presence of high concentrations of guanidine hydrochloride, it was purified to homogeneity by consecutive chitin- and immunoaffinity chromatographies. Immunofluorescence microscopy revealed that the enzyme specifically binds to crystalline alpha-chitin within fungi and other organisms as well as to beta-chitin, but not to colloidal chitin, chitosan, various types of cellulose, or other polysaccharides. The amino acids deduced from the highly specific binding domain (12 kDa) of this enzyme do not share significant similarity with any known region interacting with chitin or another substrate. During cultivation with chitin, the 59-kDa enzyme is proteolytically processed to a 47-kDa truncated chitinase lacking the chitin-binding domain. The 47-kDa enzyme hydrolyses crystalline chitin considerably less efficiently than the 59-kDa enzyme, whereas colloidal chitin and low-molecular-mass substrates are quite equally degraded by both enzymes at identical optimal pH (7.3) and temperature (45-55 degrees C) values. Thus a strong adhesion of the enzyme to its crystalline substrate via its binding domain is a prerequisite for efficient hydrolysis.

Mining marine shellfish wastes for bioactive molecules: Chitin and chitosan ndash; Part A: extraction methods

Abstract: Legal restrictions, high costs and environmental problems regarding the disposal of marine processing wastes have led to amplified interest in biotechnology research concerning the identification and extraction of additional high grade, low-volume by-products produced from shellfish waste treatments. Shellfish waste consisting of crustacean exoskeletons is currently the main source of biomass for chitin production. Chitin is a polysaccharide composed of N-acetyl-D-glucosamine units and the multidimensional utilization of chitin derivatives including chitosan, a deacetylated derivative of chitin, is due to a number of characteristics including: their polyelectrolyte and cationic nature, the presence of reactive groups, high adsorption capacities, bacteriostatic and fungistatic influences, making them very versatile biomolecules. Part A of this review aims to consolidate useful information concerning the methods used to extract and characterize chitin, chitosan and glucosamine obtained through industrial, microbial and enzymatic hydrolysis of shellfish waste.

Effect of Polyoxin D on Chitin Synthesis and Septum Formation in Saccharomyces cerevisiae

Abstract: The normal sequence of cell separation in Saccharomyces cerevisiae begins with the formation of a primary septum, presumably consisting of chitin, on which secondary septa are later deposited. In the presence of the antibiotic polyoxin D, a potent inhibitor of chitin synthetase, pairs of abnormal cells of two different types were observed by phase-contrast microscopy: the “exploded pair,” consisting of two lysed cells from which the cytoplasm had been extruded at the cell junction, and the “refringent pair,” consisting of two highly refractile cells joined by a thin bridge. Thus, in both cases the septal region appears to be affected. Observations with the electron microscope showed that the primary chitin septum was not formed in either of these cell types, and as a consequence secondary septa of varying thicknesses were laid down in an abnormal pattern. With [ 3 H]glucose as carbon source the incorporation of tritium into the chitin of abnormal cells was inhibited about 90%, whereas the labeling of mannan was normal and that of glucan somewhat reduced. The effective concentrations of polyoxin D (0.1 to 1 mg/ml) were much greater than those required to inhibit chitin synthesis in vitro. Dimethylsulfoxide and amphotericin B, both known to increase cell permeability, enhanced the action of the antibiotic. Images

Use of chitin and chitosan in lobster shell wastes for color removal from aqueous solutions

Abstract: Chitin and chitosan prepared from lobster shell wastes were used as adsorbents for the removal of various dyes from aqueous solutions. It was shown that high adsorption capacities were observed for reactive dyes. The adsorption equilibrium data could be well described by Langmuir equation under the concentration range investigated (50–500 mg/L). On the basis of Langmuir adsorption capacity, chitosan obtained in this work was found to be more effective compared to chitin and a commercial chitosan.