Chitosan depolymerization by enzymes from hepatopancreas of the crab Paralithodes camtschaticus

An enzyme preparation was isolated from the Paralithodes camtschaticus hepatopancreas that exhibited chitinase and chitosanase activities. Treatment of chitin and chitosan with this preparation decreased their viscosity-average molecular weights by 96 and 41%, respectively. The chromatographic profiles of the products of chitin and chitosan hydrolysis suggested that the crab hepatopancreas in rich in endochitinases. Enzymatic digestion of chitosan increased its solubility and moderately reduced the extent of its acetylation. A mathematical approach was proposed for calculating the molecular weights of chitosan fractions from weight-average molecular weights determined viscometrically.     

Properties of chitinolytic enzymes from the hepatopancreas of the red king crab (<Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis>)

Our study confirms the presence of chitinolytic, chitosanolytic, and deacetylase activities in the hepatopancreas of the red king crab, related to the specific diet of this species. The maximum rate of chitin/chitosan hydrolysis by an enzyme preparation from crab hepatopancreas occurs at 36.5–37.0°C. Two pH optimums have been found for the enzymatic reaction under mildly alkaline and acidic conditions for both exo-and endochitinase activities. The enzyme preparation is most affine to partly deacetylated chitin with an acetylation degree within 40–50%.     

Properties of chitinolytic enzymes from the hepatopancreas of the red king crab (Paralithodes camtschaticus)

Our study confirms the presence of chitinolytic, chitosanolytic, and deacetylase activities in the hepatopancreas of the red king crab, related to the specific diet of this species. The maximum rate of chitin/chitosan hydrolysis by an enzyme preparation from crab hepatopancreas occurs at 36.5-37.0 degrees C. Two pH optimums have been found for the enzymatic reaction under mildly alkaline and acidic conditions for both exo- and endochitinase activities. The enzyme preparation is most affine to partly deacetylated chitin with an acetylation degree within 40-50%.     

Synthesis of exo-β-glucosaminidase BY FUNGUS <Emphasis Type="Italic">Penicillium</Emphasis> sp. IB-37-2

A new strain Penicillium sp. IB-37-2, which actively hydrolyzes chitosan (SD ～80–85%) but possesses low activity against colloidal chitin, was isolated. The fungus was observed to have a high level chitosanase biosynthesis (1.5–3.0 U/mL) during submerged cultivation at 28°C, with a pH of 3.5–7.0 and 220 rpm in nutrient media containing chitosan or chitin from shells of crabs. Purification of the chitosanase enzyme complex from Penicillium sp. IB-37-2 by ultrafiltration and hydrophobic chromatography, followed by denaturing electrophoresis, revealed two predominant proteins with molecular weights of 89 and 41 kDa. The purified enzyme complex demonstrated maximal activity (maximal rate of hydrolysis of dissolved chitosan) and stability at 50–55°C and a pH of 3.5–4.0. The enzyme preparation also hydrolyzed laminarin, β-(1,3)-(1,4)-glycan, and colloidal chitin. Exohydrolysis of chitosan by the preparation isolated from Penicillium sp. IB-37-2 resulted in the formation of single product, D-glucosamine.     

Glycolytic activity of enzyme preparation from the red king crab (Paralithodes camtschaticus) hepatopancreas

Enzyme preparation exhibiting glycolytic activity yielding chitooligosaccharides along with N-acetyl-D-glucosamine was obtained from the red king crab (Paralithodes camtschaticus) hepatopancreas. The results of the analysis confirmed the presence of endo- and exochitinase activities in the preparation. HPLC showed that the hydrolysis products of chitin and chitosan did not contain D(+)-glucosamine, which is indicative of the absence of deacetylase and, apparently, exochitosanase activities. A comparison of the dependence of the enzyme preparation activity on temperature and pH of the incubation medium suggests that chitinase and protease activities are exhibited by different enzymes.     

Fabrication and properties of a porous chitin/chitosan conduit for nerve regeneration

A porous, biodegradable, natural chitin/chitosan nerve conduit was constructed. Scanning electron microscopy confirmed that it was homogeneous and highly porous. FT-IR spectra showed that there were no residues arising from the preparation process in the conduit. Addition of chitin to the chitosan solution increased the mechanical strength and maximum tensile strength from 7.2 to 9.6 MPa. Preliminary animal tests indicated that porous chitin/chitosan conduits did not swell in vivo and were compatible with surrounding tissue.     

Extracellular proteinase and chitinase produced by a culture ofStreptomyces kurssanovii

Extracellular enzymes—a chitinase and a proteinase with molecular weights 22 and 32 kDa, respectively—were isolated fromStreptomyces kurssanovii cells. After purification on modified regenerated chitin, the enzymes were virtually homogeneous according to denaturing PAGE. Both enzymes were found to degrade chitosan.     

Chitin and chitosan biopolymer production from the Iranian medicinal fungus Ganoderma lucidum: Optimization and characterization

Abstract

Chitin and chitosan with unique properties and numerous applications can be produced from fungus. The production of chitin and chitosan from the mycelia of an Iranian Ganoderma lucidum was studied to improve cell growth and chitin productivity. Inoculum size and initial pH as two effective variables on the growth of G. lucidum and chitin production were optimized using response surface method (RSM) by central composite design (CCD). The results verified the significant effect of these two variables on the cell growth and chitin production. In optimum conditions, including pH?=?5.7 and inoculum size of 7.4%, the cell dry weight was 5.91?g/L and the amount of chitin production was 1.08?g/L with the productivity of 0.083?g/(L day). The produced chitin and chitosan were characterized using XRD and FTIR. Moreover, the antibacterial activity of the produced chitosan was investigated and compared with the commercial chitosan. The results showed that the produced chitin and chitosan had suitable quality and the Iranian G. lucidum would be a great source for safe and high-quality chitin and chitosan production.     

Glycolytic activity of enzyme preparation from the red king crab (<Emphasis Type="Italic">Paralithodes camtschaticus</Emphasis>) hepatopancreas

Enzyme preparation exhibiting glycolytic activity yielding chitooligosaccharides along with N-acetyl-D-glucosamine was obtained from the red king crab (Paralithodes camtschaticus) hepatopancreas. The results of the analysis confirmed the presence of endo- and exochitinase activities in the preparation. HPLC showed that the hydrolysis products of chitin and chitosan did not contain D(+)-glucosamine, which is indicative of the absence of deacetylase and, apparently, exochitosanase activities. A comparison of the dependence of the enzyme preparation activity on temperature and pH of the incubation medium suggests that chitinase and protease activities are exhibited by different enzymes.     

Preparation and physico-chemical characterization of chitin and chitosan from the pens of the squid species, Loligo lessoniana and Loligo formosana

β-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. Without deminerization due to negligible ash content, only deproteinization was used in the chitin isolation with an yield of 35–38%, without significant difference either between the two species or the collection seasons. Reducing step not only saves production cost but also obviates acid pollutant. Mild alkaline deacetylation with various time periods was employed in the chitosan preparation. Optical rotation and thermal transition of chitin from both species suggested the weak intermolecular forces compared with shrimp chitin. The results of nitrogen contents indicate the effectiveness of the deproteinization method used. The samples were categorized as a Class III: moderate hygroscopicity. Traces of elements presented in pens markedly decreases but are incapable to be got rid of within the step of chitin–chitosan preparation. In addition, a small amount of cadmium, as the contamination, was detected in the samples from L. formosana.     

Effect of molecular weight of chitosan with the same degree of deacetylation on the thermal, mechanical, and permeability properties of the prepared membrane

Different molecular weight, 90% deacetylated chitosans were obtained by ultrasonic degradation on 90% deacetylated chitosan at 80 °C for various times.

Ninety percent deacetylated chitosan was prepared from alkali treatment of chitin that was obtained from red shrimp waste. Number average-, viscosity average- molecular weights were measured by gel permeation chromatography and the viscometric method, respectively. Degree of deacetylation was measured by the titration method. Enthalpy, maximum melting temperature, tensile strength and elongation of the membranes, flow rate of permeates and water are properties measured to elucidate the effect of molecular weight of chitosan on the above thermal, mechanical, and permeation properties, respectively of the prepared membranes. Results show tensile strength, tensile elongation, and enthalpy of the membrane prepared from high molecular weight chitosans were higher than those from low molecular weight. However, the permeability show membranes prepared from high molecular weight chitosans are lower than that from those of low molecular weight.     

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。     

Deacetylation of Chitin under Homogeneous Conditions

Chitin isolated enzymatically from Antarctic krill shells was dissolved in aqueous NaOH by freezing and thawing to create homogeneous conditions. Deacetylation was performed at room temperature or under heating. The degree of deacetylation, molecular weight, and dynamic viscosity of solutions were estimated in chitosan samples. Deacetylation of chitin under homogeneous conditions was optimized. Chitosans with molecular weights of 180–220 and 250–300 kDa were obtained from the chitins of Antarctic krill and northern shrimp, respectively.     

Solid-state characterization of chitosans derived from lobster chitin

Two samples of chitosan (CH1 and CH2) of different molecular weights and degrees of deacetylation were prepared from lobster chitin under two different processes. Solid-state properties of CH1 and CH2 were characterized and compared with four commercial chitosans prepared from crab and fresh shrimp shells. Infrared spectroscopy (IR), solid-state CP-MAS ¹³C NMR, powder X-ray diffraction and differential scanning calorimetric techniques were used to characterize the molecular structure and solid-state properties of the materials. Changes in the crystallinity and polymorphic forms of CH1 and CH2 were attributable to the different process conditions used. The differences in crystallinity were confirmed by powder X-ray diffraction data. The methods of preparation of CH1 and CH2 did not significantly influence the bulk, tap and true densities of the bulk material, but they affected the flow properties of CH1 and CH2. In conclusion, the physicochemical properties of the present chitosans prepared from lobster chitin (CH1 and CH2) are comparable with those of commercial chitosan materials of crab or shrimp shell origin.     

Purification and some properties of chitinase produced by Vibrio sp.

Chitinase was purified from the culture filtrate of a Vibrio sp. isolated from soil and its enzymatic properties were examined. The molecular weight measured by SDS-gel electrophoresis was approximately 100,000. The chitinase hydrolyzed colloidal chitin, chitin powder, chitosan and chitin oligosaccharides more than chitotriose but did not hydrolyze glycolchitin and chitobiose.     

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.     

Extraction of chitin and chitosan from larval exuvium and whole body of edible mealworm,Tenebrio molitor

The purpose of this study was to investigate the production of chitin and chitosan from both the exuvium and whole body of mealworm (Tenebrio molitor) larvae. Chitin from the exuvium and whole body of T. molitor larvae was chemically extracted with acid and alkali solutions to achieve demineralization (DM) and deproteinization (DP), respectively. The average DM (%) and DP (%) on a dry weight (DW) basis was 32.56 and 73.16% from larval exuvium, and 41.68 and 91.53% from whole body, respectively. To obtain chitosan, chitin particles from the exuvium and whole body of T. molitor larva were heated at various temperatures in different concentrations of NaOH. Average chitin yields were 18.01% and 4.92% of DW from the exuvium and whole body, respectively. The relative average yield of chitosan from whole body was 3.65% of DW. On average, over 90% of chitosan derived from whole body was deacetylated. The viscosity of chitosan from whole body was ranged from 48.0 cP to 54.0 cP. The chitin content of dry and wet byproducts from whole body were 17.32% and 16.94% respectively, compared to dry weight. The chitosan contents of byproducts on a DW basis were 14.48% in dry and 13.07% in wet byproduct. These results indicate that the exuvium and whole body of T. molitor larva may serve as a source of chitin and chitosan for use in domestic animal feed.     

A chitinase with high activity toward partially<Emphasis Type="Italic"> N</Emphasis>-acetylated chitosan from a new,moderately thermophilic,chitin-degrading bacterium,<Emphasis Type="Italic"> Ralstonia</Emphasis> sp. A-471

A moderately thermophilic bacterium, strain A-471, capable of degrading chitin was isolated from a composting system of chitin-containing waste. Analysis of the 16S rDNA sequence revealed that the bacterium belongs to the genus Ralstonia. A thermostable chitinase A (Ra-ChiA) was purified from culture fluid of the bacterium grown in colloidal chitin medium. Purification of the enzyme was achieved mainly by exploiting its binding to the colloidal chitin. The molecular mass of the enzyme was estimated to be 70 kDa and the isoelectric point approximately 4.7. N-terminal amino acid sequencing revealed a sequence of ADPYLKVAYYP, which had high homology (66% identity) with that of chitinase A1 from Bacillus circulans WL-12. The pH and temperature optima were determined to be 5.0 and 70°C, respectively. The enzyme was classified as a retaining glycosyl hydrolase and was most active against partially N-acetylated chitosans. Its activities towards the partially N-acetylated chitosans, i.e. chitosan 7B, chitosan 8B, and chitosan 9B, were about 11-fold, 9-fold, and 5-fold higher than towards colloidal chitin, respectively. Ra-ChiA cleaved (GlcNAc)₆ almost exclusively into (GlcNAc)_2. Activation of Ra-ChiA was observed by the addition of 1 mM Cu²⁺, Mn²⁺, Ca²⁺_, or Mg²⁺. Degradation of the partially N-acetylated chitosan produced oligosaccharides with a degree of polymerization ranging from 1–8; these are products that offer potential application for functional oligosaccharide production.     

Extracellular proteinases and chitinases, produced by a Streptomyces kurssanovii culture

Extracellular enzymes--a chitinase and a protease with molecular weights 22 and 32 kDa, respectively--were isolated from Streptomyces kurssanovii cells. After purification on modified regenerated chitin, the enzymes were virtually homogeneous according to denaturing PAGE. Both enzymes were found to degrade chitosan.     

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.