Particle concentration, charge, solution chemistry (i.e. ionic strength), and the nature of organic matter (OM) are the major factors controlling particle flocculation in aqueous environments. In the present study, the nature of clay fabric associated with clay—OM interaction at a range of ionic strengths was the focus. In the flocculation experiments, the aqueous suspension of montmorillonite and chitin was mixed with NaCl/MgSO4 electrolyte solution. Advanced sample-preparation techniques and visualization methods using transmission electron microscopy were used to observe directly the micro- and nano-scale clay—OM fabric of the resulting flocs. Such direct observation elucidated the role of OM in clay flocculation; few attempts have been made in the past due to the technical difficulties in preserving the original structure. A comparison of clay fabric at two different ionic strengths of 0 and 0.14 M revealed that the individual hexagonal clay particles settled slowly with little intra-aggregate void space (void ratio: 0.07) at 0 M while rapid flocculation and settling of clay particles at 0.14 M, with or without OM, resulted in a more open fabric with greater void space (void ratio: 0.33). The silver-staining technique demonstrated effectively the location of electron-transparent chitin in montmorillonite aggregates. Chitin appeared to link the face-to-face (FF) contacts of clay domains by bridging between negatively charged face surfaces. However, the resultant void ratio and the average hydrodynamic diameter (dH) values were lower than in the OM-free system after flocculation. The results indicated that the interplay between ionic strength and OM content affected the floc architecture and void ratio.

The present study aimed to evaluate the effects of chitosan instead of microbial inoculants on fermentation profile, losses, chemical composition, in vitro degradation, and aerobic stability of sugarcane silage (SS). Forty experimental silos (PVC tubes with 28 cm i.d., 25 cm height) were used in a randomized block design to evaluate the following treatments: (I) Control (CON): SS with no additive; (II) LB: SS ensiled with 5.0 × 105 colony forming units (CFU) of Lactobacillus buchneri (NCIM 40788)/g as-fed; (III) LPPA: SS ensiled with 1.6 × 105 CFU of L. plantarum and 1.6 × 105 CFU of Pediococcus acidilactici/g as-fed; and (IV) Chitosan (CHI): SS ensiled with 6 g/kg dry matter (DM) of chitosan. Microbial inoculation of SS reduced (P ≤ 0.05) silage pH relative to CON and CHI treatment. The LPPA decreased ammonia-nitrogen and LB decreased (P ≤ 0.05) ethanol content and increased acetic acid content relative to other treatments. The LPPA-silos had higher (P ≤ 0.05) gas losses and lower (P ≤ 0.05) DM recovery than other treatment silos. Consequently, LPPA reduced (P ≤ 0.05) DM and non-fibre carbohydrates and increased (P ≤ 0.05) neutral detergent fibre (NDF) silage content compared to other treatments. Treatments did not affect (P ≥ 0.212) DM and NDF in vitro degradation and silage pH after aerobic exposure. However, LB reduced silage temperature after aerobic exposure. Thus, LB reduces alcoholic fermentation and improves SS aerobic stability. Inoculation of LPPA reduces DM recovery and negatively affects SS chemical composition. Although CHI positively affects SS conservation relative to CON, it shows higher gas losses and decreased SS temperature after aerobic exposure compared to LB.

Bovine κ-casein glycomacropeptide (GMP) is a sialic acid containing glycopeptide, which is considered as a health promoting compound found in cheese whey. The study described in this research communication was undertaken to determine whether GMP with undetectable level of contaminating protein or phenylalanine can be isolated from bovine whey fraction using batch anion exchange technique with chitin as an adsorbent. A soluble whey fraction (SWF) prepared from 1 g whey protein isolate (WPI) was mixed with a slurry of 1 g chitin, and the mixture was incubated at pH 3.0. After incubation, the mixture was filtered, and the residue obtained (containing chitin-GMP complex) was washed with water and eluted stepwise with 0.5 M NaCl and 2.0 M NaCl. Most of GMP (corresponding to 75.8% of total sialic acid recovered) was eluted with 0.5 M NaCl. The recovered GMP accounted for 5.4% dry weight of WPI (or 18.9% dry weight of SWF). Amino acid analysis showed that there was no detectable level of contaminating amino acids including phenylalanine, histidine, arginine and tyrosine in the GMP fraction. It was concluded that the batch anion exchange method with chitin developed in this study can be used for the isolation of high purity GMP from bovine SWF.

Chitinases are found in species from all kingdoms, including Kingdom Animalia. We purified chitinase, poly [1,4-(N-acetyl-β-d-glucosaminide)] glycanohydrolase, by cation exchange chromatography on SP-Sepharose from the integument of a lepidopteran, the Mediterranean flour moth, Ephestia kuehniella Zeller, and further characterized it. Ephestia kuehniella chitinase has similar properties to other insect chitinases, with respect to the molecular mass. Its molecular mass was 79.7 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The optimum pH and temperature for activity were 6 and 40 °C, respectively. The purified enzyme exhibited stability at a pH range from 4.5 to 8.0 and showed high sensitivity to Co2+, Mn2+, Ca2+, Hg2+ and Ag+. The Km and Vmax values of E. kuehniella chitinase were, respectively, 3.98 mg/mL and 7.11 μmol/min/mg for colloidal chitin. In comparison to the values determined for the substrate affinity, the enzyme had a 2.36-fold higher affinity for Carboxymethyl–Chitin–Remazol Brilliant Violet (CM–Chitin–RBV) as a soluble substrate. We examined the antibacterial effect of E. kuehniella chitinase on the growth of both Gram-positive and Gram-negative bacteria. The enzyme inhibited the growth of Bacillus subtilis, Bacillus thuringiensis and Escherichia coli, where the average diameter of inhibition zone was 20, 23 and 19 mm, respectively. The antimicrobial effect and chitinase activity strengthen the hypothesis that the enzyme could be used in biological control against plant pests.

Chitin is a natural polysaccharide found in many diverse phyla and almost always occurs in association with protein. In this study the chitin polymer is characterized by X-ray diffraction from its naturally occurring unprocessed state through various steps used in the purification procedure. In addition, the effect of different treatments on the final product is examined. These studies show that native chitin has a characteristic diffraction pattern that is not altered by the mild treatments used to isolate relatively pure chitin. Chitins prepared from different sources exhibit the same characteristic diffraction pattern. In addition, chitin films prepared using non-degrading solvents retain most of the characteristic patterns. De-acylation of chitin to produce chitosan results in large changes to the diffraction pattern. To a very limited extent features present in the diffraction pattern of native chitin can be recovered by re-acylation of chitosan.

Several hydroid species live associated with many organisms, including bacteria. Hydroid–bacteria associations were searched for in twenty Hydrozoa species that were collected in the northern Ionian Sea and observed under blue light excitation. Of these, six showed high fluorescence on the outer perisarc, five appeared medium fluorescent, four were slightly fluorescent, and five did not show any fluorescence. Luminous bacteria were isolated and counted from the surface of the fluorescent hydroids. Their association with hydrozoan species could be explained by their feeding activity on the chitinous structures of the perisarc, as previous research on the hydroid Aglaophenia octodonta showed. Moreover, microalgae were always recovered together with luminous bacteria in the strongly, medium and slightly fluorescent hydroids. Further studies will be undertaken to characterize the luminous bacteria isolated from the surface of the examined hydrozoans as well as to better understand whether their interaction with hydroids is only related to chitin utilization or if their coexistence with microalgae in hydrozoans has an ecological meaning.

The present review is based on results of several years of investigation on the pathogenesis of plant wilt diseases using for one of the main aspects, several labeling techniques at the ultrastructural level: autoradiography with 3H-thymidine; gold-tagged lectins, enzymes, polyclonal, and monoclonal antibodies. Thus, opaque matter (OM), labeling for DNA with the appropriate markers, can be abundant in and associated with host tissue reactions and pronounced alterations (particularly in newly differentiated xylem). The presence of structures (called P-elements) in OM, paralleled by a similar occurrence in nuclei of both the host and pathogen cells, is considered as being also indicative of a cytoplasmic nature for this OM and most likely originating from fungal elements.

In Ascaris suum chitin is formed in the zygote immediately after oocyte fertilization, and its synthesis is completed in the eggs from the distal half of the uterus. Incorporation of radiocarbon [C] glucose into chitin of the eggshell was 40-fold higher than incorporation of [C] glucosamine. The same rank order also holds for the incorporation of label from these isotopes into the glycogen of the ovaries. A large part of the radiolabel was incorporated first into oocyte glycogen and only after fertilization was it incorporated into eggshell chitin. Actinomycin D inhibited chitin synthesis in the eggs from the distal half of the uterus and it significantly reduced incorporation of radiocarbon from glucose into chitin.

Antibodies to detect pectin in present investigations attached to distinct fibrils in vessel lumina. In carnation infected with an isolate of Fusarium oxysporum f.sp., labeling of pathogen cells also occurred; in a resistant cultivar (cv.), it was coincident with proximate pectin fibrils and linked to altered fungal walls, which was the opposite in the susceptible cv., indicating that hindrance of pathogen ability to degrade pectin may be related to resistance. Labeling of the fungus in culture was nil, except in media containing pectin, showing that pectin is not native to the pathogen. Labeling of fungal walls for cellulose in elm (inoculated with Ophiostoma novo-ulmi) and carnation also occurred, linked to adsorbed host wall components. The chitin probe often attached to dispersed matter, in vessel lumina, traceable to irregularly labeled fungal cells and host wall degradation products. With an anti-horseradish peroxidase probe, host and fungal walls were equally labeled, and with a glucosidase, differences of labeling between these walls were observed, depending on pH of the test solution. Fungal extracellular matter and filamentous structures, present in fungal walls, predominantly in another elm isolate (Phaeotheca dimorphospora), did not label with any of the probes used. However, in cultures of this fungus, extracellular material labeled, even at a distance from the colony margin, with an anti-fimbriae probe.

The biochemical composition of Daphnia magna Straus, the dominant planktonic crustacean of the waste stabilisation pond of Differdange (Grand-Duchy of Luxembourg), was quantitatively determined from October 1993 to July 1994. Over the sampling period, the average composition (mean ± S.D.) was 271 ± 64 mg proteins.g-1 dry weight (DW), 100 ± 28 mg lipids.g-1 (DW), 96 ± 58 μg carotenoids.g-1 (DW), 49 ± 14 mg chitin.g-1 (DW) and 125 ± 78 mg ash.g-1 (DW). The seasonal variations of the biochemical composition were related to several ecological variables (water temperature, dissolved oxygen concentration, pH, water transparency, chlorophyll a concentration and D. magna biomass). The chitin content was positively correlated to the water temperature as a result of the strong influence of this later variable on the moulting rate of the daphnids and, subsequently, on the chitin synthesis by these organisms. The carotenoid content was positively correlated to the water transparency as a result of their photoprotective role in daphnids. The fluctuations of the lipid, protein and ash levels in D. magna depended to the food availability. Despite a seasonal variation in the biochemical composition, D. magna appeared to have adequate lipid and protein levels to be used in aquaculture. Its carotenoid content is similar to fish meals used to color salmonid flesh and these organisms could be used for this purpose. The prospect of using D. magna for chitin extraction is worth considering with respect to its significant chitin content, especially if highly valuable applications are aimed.

Genomic DNA from spores of the endomycorrhizal fungus Gigaspora margarita was amplified with two sets of degenerate primers designed on conserved regions of chitin synthase polypeptides. Three chitin synthase (chs) gene portions were identified: Gimchs1, Gimchs2 and Gimchs3, encoding one class II and two class IV chitin synthases, respectively. Gimchs1 and Gimchs3 transcripts were detected by reverse transcription polymerase chain reaction (RT-PCR) during root colonization, whereas none of three mRNAs was revealed during spore germination. The potential role of the genes expressed is discussed in the light of morphogenetic and signalling events.

We have studied the chitin and ergosterol contents of ectomycorrhizal roots in three sets of experiments to evaluate them as indicators of fungal biomass. The first set of experiments showed that ageing had a marked effect on ergosterol concentrations. The ergosterol content of 7-month-old, brown, shrunken Pinus sylvestris L.–Paxillus involutus (Fr.) Fr. mycorrhizas was found to be only 10% of that found in white, turgid, 1- or 4-month-old specimens. This supports the hypothesis that the compound is a good indicator of living fungal biomass. Ageing had a lesser effect on chitin concentrations since the chitin levels found in 7-month-old mycorrhizas were still 60% of the levels found in 1- and 4-month-old specimens.

Consequently, the chitin[ratio ]ergosterol ratio increased from about 14 to 19 in 1- and 4-month-old mycorrhizas respectively to about 110 in 7-month-old mycorrhizas. In the second set of experiments, we found that variation in plant growth had no effect on the chitin[ratio ]ergosterol ratio in whole root systems of either Alnus incana (L.) Moench or Pinus sylvestris mycorrhizal with Paxillus involutus. In the third set of experiments, we found a constant relationship between the two marker concentrations in 10-month-old root systems of Pinus sylvestris, regardless of fungal species involved, using Paxillus involutus, Piloderma croceum Erikss. & Hjorts and Suillus variegatus (Fr.) O. Kuntze as test organisms. Taken together, the results of this study suggest that both chitin and ergosterol give reliable, but different, relative measures of fungal biomass in mycorrhizal roots. Furthermore, we demonstrate that, in combination, the two chemical markers can be used to estimate both total and living fungal biomass (derived from the chitin[ratio ]ergosterol ratio).

Measurements of the chitin content of the rooting horizons of a typical mor-humus heathland soil, indicate that chitin can contain in excess of 20% of the total nitrogen in the litter (L) horizon and 30% in the fermentation (F) horizon. Much of this chitin-nitrogen is thought to be contained in the mycelial walls of soil fungi.

Experiments were therefore designed to test the hypothesis that such sources of N could be rendered accessible to the ericaceous plants by their fungal endophytes. Mycelium of the ericoid endophyte Hymenoscyphus ericae (Read) Korf & Kernan and of the ectomycorrhizal fungus Suillus bovinus (Fr.) O. Krantze were grown in liquid culture before being killed and added either in the intact condition, or after fractionation, as sole sources of N to sterile media upon which were grown H. ericae in pure culture, or mycorrhizal and non-mycorrhizal plants of Vaccinium macrocarpon Ait. and Calluna vulgaris L. The abilities of the test organisms to utilize the nitrogen contained in the intact mycelial necromass, or in its fractions, were assessed by determining their yields and nitrogen concentrations of their tissues.

It was revealed that H. ericae was able to produce significantly higher yield when grown on intact fungal necromass than when provided with equivalent concentrations of N in the form of ammonium. Its yields on mycelial fractions were lower, but still significantly greater than those obtained in the controls lacking N. Significantly greater yields and N contents were also found in the ericaceous plants grown with these nitrogenous substrates in the mycorrhizal condition. Without H. ericae they had no access to the substrates. The possible ecological implications of these results are discussed.

Broiler chickens were fed on a control diet based on maize and maize starch or diets containing chitin, or 94, 82 or 76% deacetylated chitin (chitosans) with different viscosities (360, 590 and 620 m Pa.s respectively) at an inclusion level of 30 g/kg. Animals had free access to feed and water for the whole experimental period. On days 10 and 18 of the experiment chickens given the control and chitin-containing diets weighed more, had consumed more feed and had lower feed conversion ratios (g feed/g weight gain) than chitosan-fed birds. Feeding of chitosan-containing diets generally reduced total plasma cholesterol and high-density-lipoprotein (HDL)-cholesterol concentrations and gave an increased HDL:total cholesterol ratio in comparison with chickens given the control and chitin-containing diets. However, no significant reductions in plasma triacylglycerol concentrations resulting from feeding of the chitosan-containing diets were observed. The reduction in total cholesterol concentration and increased HDL: total cholesterol ratio were probably caused by enhanced reverse cholesterol transport in response to intestinal losses of dietary fats. The suggestion that dietary fat absorption was impeded by the chitosans was strengthened by the observation that ileal fat digestibility was reduced by 26% in comparison with control and chitin-fed animals. In a plasma triacylglycerol response study on day 21, feeding of 94 and 76%-chitosan-containing diets generally reduced postprandial triacylglycerol concentrations compared with chickens given the chitin-containing diet. Duodenal digestibilities of nutrients amongst chickens given the chitin-containing diet were generally lower than those of control and chitosan-fed birds indicating decreased intestinal transit time. The reduced caecal short-chain fatty acid concentrations of chickens given chitosan diets compared with the control diet illustrates the antimicrobial nature of chitosan. The fact that the three chitosan-containing diets affected the registered variables similarly indicated that the level of inclusion of chitosans in the diet exceeded the level at which the effect of the different viscosities could be significant.

Bien que la chitine soit synthétisée par un grand nombre d'espèces animales, unicellulaires ou métazoaires, appartenant notamment aux groupes zoologiques de la lignée des Coelomates Spiralia, la production de chitine en milieu marin est essentiellement due aux Crustacés. Une étude comparée des quelques données analytiques disponibles a permis de tenter de calculer les valeurs de biomasse et de production de chitine dans quelques grands types d'écosystèmes marins, et d'évaluer ainsi l'importance quantitative de la chitine dans les cycles biogéochimiques du carbone et de l'azote. Les principales données actuellement disponibles concernent le plancton de la baie de Calvi (Corse) en Méditerranée, le krill arctique et antarctique, une population de langoustes des côtes de l'Afrique du Sud, et les communautés benthiques infralittorales à algues photophiles des côtes rocheuses de la Corse. Dans tous les cas, la production de chitine a pu être estimée à environ 1g par an et par m2 de substrat rocheux ou de surface océanique. Sur base de ces valeurs de production et de l'étendue relative des principaux écosystèmes marins, la productiontotale annuelle de chitine par les crustacés marins a été évaluée à ± 2,3 milliards de tonnes.