Chitin Concentration Research Articles

Effects of chitin and its soluble derivatives on survival of Vibrio cholerae O1 at low temperature.

Chitin concentrations greater than 0.04% (wt/wt) protected cholera vibrios against killing at low temperature. This protective effect was detected with both the soluble form of chitin, glycol chitin, and the insoluble particulate form of chitin. Some amino acids or peptides also showed the same protective effect.

Method for measuring microbial degradation and mineralization of14C-labeled chitin obtained from the blue crab,Callinectes sapidus

A method for measuring microbial degradation and mineralization of radiolabeled native chitin is described.(14)C-labeled chitin was synthesized in vivo by injecting shed blue crabs (Callinectes sapidus) with N-acetyl-D-[1-(14)C]-glucosamine and allowing for its incorporation into the exoskeleton. The cuticle had a total organic carbon content of 0.48 mg C mg(-1) with a specific radioactivity of 6,356 CPM mg(-1). Glucosamine, i.e., chitin content as determined colorimetrically, was 22% (w/w). Microbial degradation and mineralization rates were assessed in batch culture using(14)C-chitin as substrate and York River water as inoculum. Replicate flasks were sampled daily for enumeration of chitinoclastic bacteria and the radiolabel recovered as particulate(14)C-chitin or(14)CO2. The amount of(14)CO2 generated was directly proportional to the loss of particulate(14)C-chitin, with 96% of the added label recovered as the sum of both phases. The maximum rate of mineralization was 207 mg day(-1) g(-1) seeded(14)C-chitin at 20°C. Highest chitinoclastic bacterial counts corresponded to the period of maximum rate of chitinolysis. It is suggested that the rate of chitin mineralization is limited by exoenzymatic depolymerization and not by chitin concentration.

Increased chitinase production by a non-pigmented mutant ofSerratia marcescens

Abstract Ultraviolet light and nitrosoguanidine were used to mutagenize a red pigmented culture of Serratia marcescens , strain EB415, which produced chitinase. After mutagenesis, a stable, non-pigmented mutant designated BL40 was isolated which produced larger colonies and zones of clearing on solid medium containing colloidal chitin. In liquid medium with colloidal chitin as the sole carbon source both strains grew similarly but BL40 produced 160 units/ml of chitinase compared with 60 units/ml for EB 415, an increase of 167%. When chitin concentration was increased in the medium, chitinase production also increased. Chitinase appeared to be extracellular, since the supernatant from washed, sonicated cells for both strains showed no detectable amount of chitinolytic activity.

Functional Properties of Chitin and Chitosan

ABSTRACTChitin (poly‐β (1⇒4)‐N‐acetyl‐D‐glucosamine), chitosan (deacetylated chitin) and microcrystalline chitin (redispersible chitin powder) were compared with microcrystalline cellulose to examine the use of those cellulose‐like biopolymers as functional additives for potential application in food formulations. Water binding, fat binding and emulsifying properties were studied. Baking tests were performed with 0.5–2.0% (flour basis) of microcrystalline chitin added to wheat flour bread or to potato protein fortified (8% potato protein concentrate) white bread. Water‐binding capacity and fat binding capacity of chitin, chitosan and microcrystalline chitin ranged from 230–440s (w/w) and from 170–315% (w/w). Chitosan and chitin did not produce emulsions but microcrystalline chitin showed good emulsifying properties and was superior to microcrystalline cellulose. Increasing concentration of microcrystalline chitin (0.12–0.8 g/100 ml water) had a positive effect on emulsion stability. Addition of microcrystalline chitin increased specific loaf volume of white bread and protein fortified breads. Water addition of 65% (flour basis) was found to be optimum for “chitin breads.”

Effect of Reaction Conditions on Hydrolysis of Chitin by Serratia marcescens QMB 1466 chitinase

ABSTRACTThe hydrolysis of chitin by Serratia marcescens chitinase was studied as part of ar overall project to develop a chitin waste treatment bioconversion scheme. Hydrolyses were conducted with automatic pH control in stirred flasks. Parameters varied were temperature, enzyme activity, and chitin particle size and concentration. A temperature of 30°C is suitable. Hydrolysis increases with increasing enzyme activity and chitin slurry concentration, and with decreasing particle size.

Biochemistry of insect differentiation. Requirements for high in vitro moulting fluid chitinase activity

A method for preparing chitinase substrate is described; the substrate reproducibly gives high chitinase activity under suitable conditions. For moulting fluid chitinase, these are: a chitin concentration of at least 2 mg/ml, pH 6.5, and presence of calcium; addition of an inhibitor for neutral protease is helpful. Activity may be measured in minutes, either colourimetrically or by counting acid-soluble product from in vivo labelled chitin. N- Acetylglucosamine is the chief soluble end product. Moulting fluid chitinase appears to form a complex with chitin and calcium which successfully competes with EGTA for calcium; the dissociation constant is therefore at least as low as 10 −7 M. A transient increase in product release of chitinase accompanies the first interaction of chitin, chitinase and calcium ions.

Molting fluid chitinase: A homotropic allosteric enzyme

The molting fluid of the tobacco hornworm has chitinase activity which shows allosteric behavior with chitin. A parabolic curve is obtained on a double reciprocal plot of 1 v vs. 1 [S] , and a sigmoid curve results when v (N-acetylglucosamine produced) is plotted against [S] (chitin concentration in terms of N-acetylglucosamine concentration). The Hill coefficient with insect chitin is 1.95 ± 0.08. Allostery of the chitinase enables the insect to exert additional control over the integrity of structure of its cuticle.

Variations quantitatives des principaux constituants cellulaires d'Entomophthora virulenta lors de la sporogénèse

Changes in the relative abundance of cell constituents of Entomophthora virulenta Hall & Dunn were studied during the various differentiation phases leading to the formation of zygospores. The highest total protein (43%) and nucleic acid (5.2% RNA and 0.2% DNA) concentrations were found in the exponential growth phase; these concentrations decreased regularly as the mycelium aged. The amount of lipids was four times larger at the prespore and spore stage (about 25%) than at the exponential mycelial stage. The zygospore contained a very high concentration of chitin (about 17%), three times more than the mycelial concentrations. However, the percentage of polysaccharides without chitin, but including glycogen, was higher in the deceleration phase mycelium (34%) than in the spore (25%). A physiological model of the sexual sporulation of E. virulenta based on these data has been presented.

Changes in the chemical composition of the common shore crab,Carcinus maenas, during the molting cycle

Juvenile and young adult specimens ofCarcinus maenas were kept in the laboratory under controlled conditions. The main organic constituents and their variations during the molt cycle were quantitatively determined. 1. During postmolt the chitin concentration rises rapidly (20–74 mg/g dry weight) in parallel to the dry weight (120–293 mg/g fresh weight). Both decrease again before ecdysis (Fig. 1). 2. The glycose level in the hemolymph (50–80 μg/ml) shows no significant variation during the molt cycle (Fig. 2). 3. The glycogen concentrations in integument, (14–180 mg/g dry weight), gills (5.5–66 mg/g dry weight), muscle (8.8–41 mg/g dry weight), heart (135–308 mg/g dry weight) and hemolymph (160–690 μg/ml) reach their maximum values during the premolt stage. The highest glycogen content in the midgut gland (83 mg/g dry weight) is observed immediately before and after ecdysis. Glycogen storage in heart and hemolymph, can, account for about half of the glycogen stored in the midgut gland (Figs. 3,4 and 5). 4. The lipid concentration in the hemolymph (120–440 μg/ml) and in gills (33.6–70 mg/g dry weight) rises during the premolt stage (Figs. 6 and 7). 5. The protein concentration in the hemolymph increased during premolt (9–31 mg/ml). The copper content (13–42 μg/ml) varies in parallel to the protein concentration indicating that the proportion of hemocyanin to total proteins remains constant during the molting cycle (Fig. 8).

Biosynthesis of chitin during various stages in the metamorphosis of Prodenia eridania

The relationship between chitin content and activity of the chitin synthetase enzyme was investigated in final instar larvae and pupae of Prodenia eridania. A correlation was found between changes in chitin concentration and activity of the enzyme. The maximum level of chitin and the peak activity of the enzyme occurred in the late final larvae. The concentrations of hexosamines and chitodextrins are also discussed in relation to their possible significance in chitin biosynthesis.