Partition coefficients of plant cuticles for monoterpenes

Summary Cuticle/water partition coefficients (K_c/w) for d-limonene, -pinene and -pinene were determined by an extrapolation and a desorption method. The sorption experiments were carried out with isolated angiosperm and gymnosperm cuticles and with [¹⁴C]-labelled monoterpenes, which were obtained biosynthetically. Both methods were suitable for the determination of the K_c/w of volatile hydrophobic compounds. For the angiosperm cuticles the partition coefficients are of the order of 10⁴, which indicates a high accumulation of monoterpenes in the cuticle. The values of the conifer cuticles of Picea abies (L.) Karst. and Abies alba Mill., however, are lower due to their high lignin content. This is proved by the increase of the partition coefficients after removal of polar and phenolic components. The K_c/w can be estimated with good accuracy from the octanol/water partition coefficient, which was determined experimentally.     

Thermodynamic functions of biopolymer hydration. I. Their determination by vapor pressure studies,discussed in an analysis of the primary hydration process

The primary hydration process of native biopolymers is analyzed in a brief review of the literature, pertaining to various aspects of biopolymer–water systems. Based on this analysis, a hydration model is proposed that implies that the solution conformation of native biopolymers is stable at and above a critical degree of hydration (h_p′ = 0.06–0.1 g H₂O/g polymer). This water content corresponds to the fraction of strongly bound water, and amounts to ～20% of the primary hydration sphere. In order to test this model, detailed sorption–desorption scanning experiments were performed on a globular protein (α-chymotrypsin). The results obtained are consistent with the proposed hydration model. They show that under certain experimental conditions, sorption isotherms can be obtained that do not exhibit hysteresis. These data represent equilibrium conditions and are thus accessible to thermodynamic treatment. Valid thermodynamic functions, pertinent to the interaction of water with biopolymers in their solution state, can be obtained from these sorption experiments.     

Decomposition and sorption characterization of plant cuticles in soil

The sorption of organic compounds by plant cuticular matter has been extensively investigated; however, little has been studied regarding the effect of plant cuticle degradation on their role in the sorption of organic compounds in soils. The sorption of phenanthrene was studied in soil samples which had been incubated for up to 9 months with three different types of plant cuticle isolated from tomato fruits, pepper fruits and citrus leaves. The main change in the diffuse reflectance Fourier-transform infrared (DRIFT) spectra during incubation of the cuticles was related to cutin decomposition. The peaks assigned to methyl and ethyl vibration and C=O vibration in ester links decreased with decomposition. In general, with all samples, the phenanthrene sorption coefficients calculated for the whole incubated soils (K _d) decreased with incubation time. In contrast, the carbon-normalized K _d values (K _oc) did not exhibit a similar trend for the different cuticles during incubation. The origin of the cuticle also affected the linearity of the sorption isotherms. With the tomato and citrus cuticle samples, the Freundlich N values were close to unity and were stable throughout incubation. However with the green pepper cuticle, the N values exhibited a significant decrease (from 0.98 to 0.70). This study demonstrates that the structural composition of the plant cuticle affects its biodegradability and therefore its ability to sorb organic compounds in soils. Of the residues originating from plant cuticular matter in soils, the cutan biopolymer and lignin-derived structures appear to play a dominant role in sorption as decomposition progresses. Responsible Editor: Alfonso Escudero.     

Characteristics of bacterial lipopolysaccharides depending on extraction method

Carbohydrate-containing biopolymers have been isolated from Erwinia carotovora subsp. atroseptica 549 by two methods--the aqueous-phenol and with using physiological solution--with addition and without addition of ethylenediaminetetraacetate (EDTA). The biopolymers yield from the cells of bacteria are shown to depend on the extraction method. Lipopolysaccharide-protein complex have been isolated by the sparing method. The purest lipopolysaccharide have been isolated by the aqueousphenol method. The preliminary treatment of cells by EDTA increased the biopolymers output. Carbohydrate containing biopolymers isolated from the cells of bacteria by different methods possess the similar qualitative composition of monosaccharides but they differ in the quantitative content of monosaccharides, spectrum of fatty acids of lipid components as well as in the protein content.     

Moisture Sorption Isotherms of Broccoli Interpreted with the Flory-Huggins Free Volume Theory

In this work, the Flory Huggins Free Volume theory is used to interpret the sorption isotherms of broccoli from its composition and using physical properties of the components. This theory considers the mixing properties of water, biopolymers and solutes and has the potential to describe the sorption isotherms for varying product moisture content, composition and temperature. The required physical properties of the pure components in food became available in recent years and allow now the prediction of the sorption isotherms with this theory. Sorption isotherm experiments have been performed for broccoli florets and stalks, at two temperatures. Experimental data shows that the Flory Huggins Free Volume (FHFV) theory represents the sorption isotherm of fresh and blanched broccoli samples accurately. The results also show that blanching affects the sorption isotherm due to the change of composition via leaching solutes and the change of interaction parameter due to protein denaturation.     

Enzymatic activities involved in incorporation of N-acetyldopamine into insect cuticle during sclerotization

During sclerotization of insect cuticle, N-acetyldopamine (NADA) is enzymatically oxidized before reaction with cuticular proteins. Not all oxidized NADA reacts with cuticular structural materials, a small fraction reacts with water or other available low molecular weight compounds to give soluble products. Various types of cuticle were incubated with excess NADA and the products studied by reversed phase high performance liquid chromatography (RP-HPLC) to obtain information on the enzymatic activities in the cuticle. The occurrence of at least two enzymes competing for NADA and present in different proportions in the various types of cuticle can explain the results. NADA may be incorporated into cuticle via α,β-dehydro-NADA (β-sclerotization) or via quinone methides and o-quinones, and the actual course of sclerotization will depend upon the relative activities of the enzymes involved. The various pathways may all be used simultaneously.     

Protecting against water loss: analysis of the barrier properties of plant cuticles

The cuticle is the major barrier against uncontrolled water loss from leaves, fruits and other primary parts of higher plants. More than 100 mean values for water permeabilities determined with isolated leaf and fruit cuticles from 61 plant species are compiled and discussed in relation to plant organ, natural habitat and morphology. The maximum barrier properties of plant cuticles exceed that of synthetic polymeric films of equal thickness. Cuticular water permeability is not correlated to the thickness of the cuticle or to wax coverage. Relationships between cuticular permeability, wax composition and physical properties of the cuticle are evaluated. Cuticular permeability to water increases on the average by a factor of 2 when leaf surface temperature is raised from 15 degrees C to 35 degrees C. Organic compounds of anthropogenic and biogenic origin may enhance cuticular permeability. The pathway taken by water across the cuticular transport barrier is reviewed. The conclusion from this discussion is that the bulk of water diffuses as single molecules across a lipophilic barrier while a minor fraction travels along polar pores. Open questions concerning the mechanistic understanding of the plant cuticular transport barrier and the role the plant cuticle plays in ensuring the survival and reproductive success of an individual plant are indicated.     

Viscoelastic nature of isolated tomato (Solanum lycopersicum) fruit cuticles: a mathematical model

Viscoelastic behaviour of isolated tomato fruit cuticle (CM) is well known and extensively described. Temperature and hydration conditions modify the mechanical properties of CM. Mechanical data from previous transient‐creep analysis developed in tomato fruit cuticle under different temperature and hydration conditions have been used to propose a rheological model that describes the viscoelastic nature of CM. As a composite material, the biomechanical behaviour of the plant cuticle will depend not only on the mechanical characteristics of the individual components by themselves but also on the sum of them. Based on this previous information, we proposed a two‐element model to describe the experimental behaviour: an elastic hookean element connected in parallel to a viscous element or Voigt element that will describe the mechanical behaviour of the isolated CM and cutin under the studied conditions. The main parameters of the model, E₁ and E₂ will reflect the elastic and viscoelastic behaviour of the cuticle. Relationship between these physical parameters and the change in CM properties were discussed in order to elucidate the rheological processes taking place in CM. This model describes both the influence of temperature and hydration and the behaviour of the isolated cutin and the inferred contribution of the cuticle fraction of polysaccharides when the whole cuticle is tested.     

Water Binding in Legume Seeds

The physical status of water in seeds has a pivotal role in determining the physiological reactions that can take place in the dry state. Using water sorption isotherms from cotyledon and axis tissue of five leguminous seeds, the strength of water binding and the numbers of binding sites have been estimated using van't Hoff analyses and the D'Arcy/Watt equation. These parameters of water sorption are calculated for each of the three regions of water binding and for a range of temperatures. Water sorption characteristics are reflective of the chemical composition of the biological materials as well as the temperature at which hydration takes place. Changes in the sorption characteristics with temperature and hydration level may suggest hydration-induced structural changes in cellular components.     

Sorption von Cellulase an Weizenstroh und seine Komponenten

By comparing different activity data of the buffered cellulase solution before and after contact with the substrate the interaction between Penicillium janthinellum cellulase and wheat straw, resp. its components (holocellulose and isolated lignin) has been investigated. The loss of activity due to sorption or denaturation has been found to differ widely between the different activity data and between the various substrates. A remarkable loss of enzyme activity was observed after contact with isolated straw lignin. The differences in activity decrease between the cellulose and the lignin moiety were found to be largent with the cellobiase activity.     

Leaf cuticle ultrastructure of Pseudofrenelopsis dalatzensis (Chow et Tsao) Cao ex Zhou (Cheirolepidiaceae) from the Lower Cretaceous Dalazi Formation of Jilin,China

The cheirolepidiaceous conifer Pseudofrenelopsis dalatzensis from the Lower Cretaceous Dalazi Formation, Jilin Province, Northeast China is studied in detail based on abundant material. The gross morphology of vegetative shoots shows a greater variation than previously known. Additional information of microstructure is that the adaxial cuticle from the free part of leaves is also papillate as the abaxial cuticle. The excellent preservation of cuticles allows for the first time in this family to four distinct types of cuticle in ultrastructural level: subsidiary cells, guard cells, epidermal cells with and without papillae. Based on 30 measurements the statistic approach on each type of cell cuticle, i.e. not only the total thickness of the cuticle but also details and proportions of all different layers. A key is provided using a combination of 7 significant ultrastructural characters. These results seem to be very promising for the identity of each taxon within the Cheirolepidiaceae family. The cuticular ultrastructure of this family is characterized by having a cuticle proper A composed of A1 wavy polylamellate layer and A2 granular layer, above the cuticular layer B with B1 fibrillate and B2 granular layers. The importance of ultrastructural characters at different levels of taxonomy and palaeoecology is also discussed.     

表面活性剂对链霉素在内蒙古牧区土壤中吸附解吸的影响

通过静态吸附实验,研究了3种不同类型的表面活性剂(阳离子:十六烷基三甲基溴化铵,CTAB;阴离子:十二烷基苯磺酸钠,SDBS;非离子,曲拉通100,TX-100)对链霉素(Streptomycin,STR)在内蒙古牧区土壤中吸附解吸的影响。结果表明,3种表面活性剂的存在均会增加STR在土壤中吸附的线性程度。CTAB的存在抑制了STR在土壤表面的吸附同时抑制了STR的解吸,然而SDBS的存在降低了STR在土壤中的吸附量并增加了吸附过程的可逆性。与CTAB和SDBS不同,TX-100对STR在土壤中的吸附的影响取决于其添加浓度。低浓度的TX-100对STR的吸附促进作用大于高浓度。随着TX-100浓度的增加,TX-100对STR的增溶作用加剧。促使吸附在土壤表面的STR迁移到水相中,从而抑制了STR的吸附,进而促进了STR的解吸。     

Fourier transform IR study of enzymatically isolated tomato fruit cuticular membrane

Fourier transform ir study on enzymatically isolated tomato fruit cuticle has been performed. Assignments of the observed frequencies to functional groups present in the cuticular membrane yield information on the polyester cross-links and the interactions among the different components that form this plant protective barrier. © 1992 John Wiley & Sons, Inc.     

Lignocellulose degradation by microorganisms from termite hills and termite guts: A survey on the present state of art

Abstract: In several aspects termites are a fascinating group of insects having attracted the interest of many researchers. They exhibit a complex social behavior and caste differentiation occurring elsewhere only among the hymenoptera. In an enlarged part of the hindgut, the paunch, termites have established a unique symbiotic association with prokaryotic and eukaryotic microorganisms. A similar flora is also found in wood-eating roaches of the genus Cryptocercus . The study of symbiosis between termites and their intestinal microbes is of general interest, because due to this symbiotic interaction termites can feed on complex biopolymers such as wood. Flagellates and bacteria occur in the gut of lower termites, while higher termites possess only bacteria. In particular spirochetes are abundant in the termite gut. Apart from spirochetes and other more common bacteria, actinomycetes, yeasts and fungi have also been isolated from different species of termites. This review summarizes the distinct role of the intestinal flora in degradation of wood components such as cellulose, hemicellulose and lignin.     

Dialyzability of iron, zinc, and copper of different types of infant formulas marketed in Spain

The bioavailability of trace elements in infant formulas is affected by different physiological and dietetic factors. In vitro methods based on element dialyzability have been proposed to estimate the bioavailability. Infant formulas of the same type but from different manufacturers can differ in the salt used for supplementation and in the contents of other components that can affect mineral bioavailability. The aim of our study is to estimate the dialyzability of iron, zinc, and copper of formulas marketed in Spain, in order to detect possible differences in formulas of the same type coming from different manufacturers. At the same time, the effects of the type of formula, the composition of the protein fraction, and the mineral content on the element dialyzability are also studied. Differences are found in the dialysis percentages of the elements studied in formulas of the same type but from different manufacturers. The formulas giving the highest dialysis percentages for the three considered elements are the hypoallergenic ones based on protein hydrolysates. No differences are observed in formulas having whey or casein as the main protein fraction. Significant correlations are obtained between the element contents and the dialyzability of the elements.     

Hydrogen bonding in lignin: a Fourier transform infrared model compound study

Hydrogen bonding plays an important role in the thermal and mechanical properties of biopolymers. To investigate hydrogen bond formation in lignin, an abundant natural polymer found in plants, Fourier transform infrared (FTIR) analysis of various lignin model compounds was performed. Four monomeric model compounds and one dimeric model compound were studied under various conditions. FTIR analysis revealed aliphatic hydroxyl groups form stronger hydrogen bonds than phenolic hydroxyl groups. Further, the dimeric biphenyl-type structure formed significantly stronger intermolecular hydrogen bonds as compared to the other monomeric model compounds. Results from the model compound studies were used to explain the observed complex hydrogen-bonding system present in both softwood and hardwood technical lignins. Together with chemical analysis, we discuss the difference in hydrogen bonding between hardwood and softwood lignin and the observed differences in the glass transition temperature.     

Pesticide desorption from soils facilitated by dissolved organic matter coming from composts: experimental data and modelling approach

Dissolved organic matter (DOM) interaction with pesticides was examined studying the ability of DOM to desorb 8 pesticides previously sorbed to soil. DOM was originating from municipal waste composts at two maturity degrees, recovered at 20°C and by hot-pressurised subcritical water. Pesticide desorption depended on their previous sorption on soil. When sorption was low (K_OC ≤ 50, sulcotrione, metalaxyl), water was more efficient than DOM for desorption. On the contrary, when sorption was high (K_OC ≥ 2000, trifluraline), little effect of DOM was observed. For the moderately sorbed pesticides, DOM favoured pesticide desorption compared to water. For the lowest sorbed pesticides (K_OC ≤ 100), hysteresis was increased with larger proportions of DOM extracted with subcritical-water. Dissolved organic matter extracted from fresh-immature compost had larger capacity to mobilize the sorbed pesticides than the DOM from the mature compost. The pesticide desorption resulted from the positive and competitive interactions between pesticide, DOM and soil surfaces. These interactions were modelled considering separate partitioning coefficients. A general equation allowed the deduction of specific coefficients describing interactions in solution between pesticides and the non-sorbed fraction of DOM remaining in solution. This fraction was supposed to contain the most hydrophilic fraction of DOM and was able to interact with the most polar pesticide (amitrol). When pesticide hydrophobicity increased, the partitioning between pesticide and DOM decreased. Modelling the three-phase system (liquid, DOM and solid phases) pointed out that the solid phase played the most important role on pesticide behaviour through the sorption process of DOM and pesticides.     

The effects of hemicelluloses and lignin removal on water uptake behavior of hemp fibers

This study investigated the individual influences of hemicelluloses and lignin removal on the water uptake behavior of hemp fibers. Hemp fibers with different content of either hemicelluloses or lignin were obtained by chemical treatment with 17.5% sodium hydroxide or 0.7% sodium chlorite. Various tests (capillary rise method, moisture sorption, water retention power) were applied to evaluate the change in water uptake of modified hemp fibers. The obtained results show that when the content of either hemicelluloses or lignin is reduced progressively by chemical treatment, the capillary properties of hemp fibers are improved, i.e. capillary rise height of modified fibers is increased up to 2.7 times in relation to unmodified fibers. Furthermore, hemicelluloses removal increases the moisture sorption and decreases the water retention values of hemp fibers, while lignin removal decreases the moisture sorption and increases the water retention ability of hemp fibers.     

Bifunctional in vivo role of laccase exploited in multiple biotechnological applications

Laccases are multicopper enzymes present in plants, fungi, bacteria, and insects, which catalyze oxidation reactions together with four electron reduction of oxygen to water. Plant, bacterial, and insect laccases have a polymerizing role in nature, implicated in biosynthesis of lignin, melanin formation, and cuticle hardening, respectively. On the other hand, fungal laccases carry out both polymerizing (melanin synthesis and fruit body formation) as well as depolymerizing roles (lignin degradation). This bifunctionality of fungal laccases can be attributed to the presence of multiple isoforms within the same as well as different genus and species. Interestingly, by manipulating culture conditions, these isoforms with their different induction patterns and unique biochemical characteristics can be expressed or over-expressed for a targeted biotechnological application. Consequently, laccases can be considered as one of the most important biocatalyst which can be exploited for divergent industrial applications viz. paper pulp bleaching, fiber modification, dye decolorization, bioremediation as well as organic synthesis. The present review spotlights the role of fungal laccases in various antagonistic applications, i.e., polymerizing and depolymerizing, and co-relating this dual role with potential industrial significance.

     

Heats of water vapor sorption in swelling biopolymers

Heats of water vapor sorption by three biopolymers, polygalacturonic acid, sodium hyaluronate, and calcium salt of bovine submaxillary mucin, were determined calorimetrically. These calorimetric heats of sorption were compared with the isosteric heats of sorption as a function of water uptake. Maxima in both of these functions occur at “monolayer” coverage. The differences between the calorimetric and isosteric heats are explained in terms of the irreversibility of the sorption process, especially in terms of the structural changes that occur in the biopolymers during swelling.