Study of water sorption on modified Agave fibres

Polymer composite materials are usually reinforced by synthetic matter such as carbon or glass fibres. However, owing to their good mechanical properties and low density, natural fibres are now increasingly being considered as reinforcement. With the aim of a new natural fibre based composite, various chemical treatments have been performed on Agave (Americana L.) fibres in order to improve their compatibility with the polymer matrix and to reduce their affinity for water. The effect of these treatments on the fibre water sorption power has been investigated by means of a micro-balance. Equilibrium water sorption isotherms have been deduced from weight variations of the fibres under water vapor pressure increments. Several specific physico-chemical models have been tested to describe the water sorption isotherms. The Park’s model was found to describe the experimental results accurately and over a wide activity range. The sorption kinetics was also exploited in order to evaluate the diffusivity of water in the fibres. The variation of the water diffusion coefficient with water concentration is in agreement with the triple sorption mode described by the Park’s model. These results show a global increase of moisture resistance of the fibres after chemical treatment. This effect is interpreted in terms of chemical and structural modifications of the cell-wall structure.     

Pectinase treatments on technical fibres of flax: Effects on water sorption and mechanical properties

This study is focused on enzymatically upgrading the functional properties of flax fibres. Green flax fibres were treated with a polygalacturonase and a pectate lyase (PaL) and their properties were compared with dew-retted fibres. Morphological observations, vapour-sorption analyses and mechanical measurements showed that PaL-treatment was able not only to mime retting in terms of bundle division, but also to improve the mechanical properties of technical fibres. Conversely, these properties were shifted down after the polygalacturonase treatment, mainly due to the presence of contaminating glycanases. At the level of the elementary fibres, nanoindentation data indicated the highest stiffness of the secondary wall for PaL-treated fibres. The tensile properties exhibited equal, but moderate values of the Young's modulus (∼37 ± 14 GPa) and breaking strength (∼650 ± 300 MPa) for retted and PaL-treated fibres; we hypothesize an impact of the growth conditions on the fibre chemical structure with an excess of matrix pectins compared to the amount of glucomannan coating the cellulose microfibrils.     

Determining the physical properties of flax fibre for industrial applications: the influence of agronomic practice

Field trials of fibre flax were sown in 2002 and 2003 comprising 29 and 26 flax varieties, respectively. In 2002, two nitrogen treatments of 40 and 80 kg ha^?1 were imposed. The trials were sprayed with a desiccating herbicide prior to retting at 35 and 15 days after midpoint of flowering in 2002 and 2003, respectively, and were harvested once retting had completed. Fibre was extracted from the flax stems using a laboratory‐scale scutcher and hackling pins, and long and total fibre yields were determined. The breaking load of flax technical fibres was assessed using a novel technique employing ‘zero twist’ yarns. Fineness was assessed using the Wool Industries Research Association airflow method. The tenacity of a single technical fibre was then derived from the average breaking load of the yarn and knowledge of its fineness. Both flax variety and season were found to contribute to variations in fibre fineness and strength, with the dry season in 2003 leading to less variation across the varieties and much finer fibres. Few of the varieties were found to be stable across seasons, and environmental variation accounted for 96% of the variation in fibre fineness between years, and 69% of the variation in tensile strength and breaking load. Fibre yield was found to be related to fibre fineness, with the coarser fibres corresponding to higher yields. The new yarn test presented herein has been shown to be a valid and useful method for determining the tensile properties of technical flax. The varieties and the sample sizes required to adequately measure variation in fibre properties are discussed.     

Assessment of flax and hemp fibres in terms of their impact on the growth performance and health status of weaned piglets

Weaning is a critical phase in intensive piglet production marked by the frequent occurrence of digestive disorders posing health and economic burden. To stave off such weaning-related problems, antibiotics and supplements containing high levels of ZnO are often used. In this study, we investigated whether natural fibres obtained from two plants known for their dietary fibre profile and antioxidant properties: flax (Linum usitatissimum L.) and hemp (Cannabis sativa L.), can serve as a health-promoting diet supplement. The study was conducted on a total of 191 Polish Large White piglets from 18 L, from their birth to 56 days of age. Piglets were divided by litters into six groups: W1.5, F1.5, H1.5, W2.0, F2.0, and H2.0. Groups W1.5, F1.5, and H1.5 received feed supplemented with 1.5% fibre from wood cellulose (W), flax (F), and hemp (H), respectively, while groups W2.0, F2.0, and H2.0 received feed with a higher 2.0% content of the same fibres. Flax and hemp fibres were characterised by a complex composition, antioxidant properties due to the presence of phenolic acids, and low risk of mycotoxin contamination. Flax fibre resulted in best weight gains and feed conversion ratio (P ≤ 0.05) of piglets, while hemp fibre had higher positive effect on antioxidant status (P ≤ 0.05) compared to the other two fibre additives. Neither flax nor hemp fibres had any adverse effect on the haematological and biochemical blood parameters. Piglets receiving a diet with 1.5% added fibre showed better growth performance, while diet supplementation with 2% fibre had a beneficial effect on the content of butyric acid in the small intestinal chyme (P ≤ 0.05). The results suggested that both flax and hemp fibres can be innovative feed additives for weaned piglets. However, further studies should be conducted in commercial farms, as the effects of dietary fibre could vary in more challenging environmental conditions.     

Studies on chemical and enzyme retting of flax on a semi-industrial scale and analysis of the effluents for their physico-chemical components

Retting trials carried out in this study have shown that chemical and enzyme retting could be carried out at a semi-industrial scale. The yield from enzyme retted fibres was higher than chemical or water retted flax fibres. The variation in fibre fineness, strength, fluidity and moisture regain was not significantly different, thereby proving that chemicals and enzymes do not degrade or depolymerise the cellulose chains. The activity of the enzymes at the end of retting, when investigated, remained quite high, suggesting that the waste liquor could be recycled after removing the suspended solids present in the liquor. Biochemical oxygen demand (BOD) and chemical oxygen demand (COD) were highest in effluent from enzyme retting compared to effluents from chemical or water retting. All three effluents were analysed for N₂, PO₄, Cl, SO₄, Na and K. Aeration of the effluents reduced the level of BOD and COD by more than 50%.     

Influence of fibre architecture on the biodegradability of FLAX/PLA composites

Polymers derived from renewable resources are known for their low impact on the carbon footprint as they are recyclable by decaying processes. When these materials are blended with natural fibres to form composites, they are also highly suitable for technical applications but maintain their outstanding recycling potential. However, as natural fibres increase the strength and alter the polymers' structure, they can also affect the decaying processes. The objective of this study is to investigate the influence of flax fibre reinforcements on the decaying process of poly(lactic) acid (PLA) in flax – PLA composites under composting conditions. The results indicate that the fibres enhance the biodegradation by enlarging the potential surface contributing to the decaying process. At the same time, the fibres act as channels and distribute water and microorganisms in the composite. The decaying process is attributed to fibre decomposition and hydrolysis of PLA which leads to increased degradation rates for composites with high fibre weight content.     

Enzymatic grafting of natural phenols to flax fibres: Development of antimicrobial properties

Unbleached flax fibres for paper production were treated with laccase from Pycnoporus cinnabarinus and low molecular weight phenols (syringaldehyde - SA, acetosyringone - AS and p-coumaric acid - PCA) to evaluate the potential of this treatment to biomodify high cellulose content fibres. After the enzymatic treatment with the phenols, an increase in kappa number was found, probably due to a covalent binding of the phenoxy radicals on fibres. Grafting was more evident in pulps treated with PCA (an increase of 4 kappa number points with respect to the laccase control was achieved). Paper handsheets from treated pulps showed antimicrobial activity against the bacteria tested: Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella pneumoniae. An important reduction on microbial count was obtained after incubation of liquid cultures of the bacteria with grafted handsheets. AS and PCA grafted fibres showed a high antibacterial activity on K. pneumoniae, getting a nearly total growth inhibition. AS fibres also caused a high reduction in bacterial population of P. aeruginosa (97% reduction). Optical properties of handsheets from treated pulps were also determined, showing a brightness decrease and increase in coloration, evaluated by CIE L*a*b* system, caused by the laccase induced grafting of the phenols. The results suggest that these low molecular weight phenols, covalently bound to the flax fibres by the laccase treatment, can act as antimicrobial agents and produce handsheets with antimicrobial activity.     

Treatment of cotton with an alkaline Bacillus spp cellulase: activity towards crystalline cellulose

We analysed the influence of several enzymatic treatment processes using an alkaline cellulase enzyme from Bacillus spp. on the sorption properties of cotton fabrics. Although cellulases are commonly applied in detergent formulations due to their anti-redeposition and depilling benefits, determining the mechanism of action of alkaline cellulases on cotton fibres requires a deeper understanding of the morphology and structure of cotton fibres in terms of fibre cleaning. The accessibility of cellulose fibres was studied by evaluating the iodine sorption value and by fluorescent-labelled enzyme microscopy; the surface morphology of fabrics was analysed by scanning microscopy. The action of enzyme hydrolysis over short time periods can produce fibrillation on cotton fibre surface without any release of cellulosic material. The results indicate that several short consecutive treatments were more effective in increasing the fibre accessibility than one long treatment. In addition, no detectable hydrolytic activity, in terms of reducing sugar production, was found.     

Production of N-acetyl-D-neuraminic acid by use of an efficient spore surface display system

Production of N-acetyl-d-neuraminic acid (Neu5Ac) via biocatalysis is traditionally conducted using isolated enzymes or whole cells. The use of isolated enzymes is restricted by the time-consuming purification process, whereas the application of whole cells is limited by the permeability barrier presented by the microbial cell membrane. In this study, a novel type of biocatalyst, Neu5Ac aldolase presented on the surface of Bacillus subtilis spores, was used for the production of Neu5Ac. Under optimal conditions, Neu5Ac at a high concentration (54.7 g liter⁻¹) and a high yield (90.2%) was obtained under a 5-fold excess of pyruvate over N-acetyl-d-mannosamine. The novel biocatalyst system, which is able to express and immobilize the target enzyme simultaneously on the surface of B. subtilis spores, represents a suitable alternative for value-added chemical production.     

Thermodynamic of Water Sorption of Grape Seed: Temperature Effect of Sorption Isotherms and Thermodynamic Characteristics

After determination of sorption isotherms of grape seeds using gravimetric method, five models with temperature effect were used to fit water sorption isotherms of grape seeds to investigate temperature effect on sorption isotherms and its thermodynamic characteristics. Halsey model had minimum mean relative percentage error (M _e ) and all other models used were good in fitting experimental data (with M _e of less than 10 %). Differential parameters such as net isosteric heat, isosteric heat, differential entropy and integral function such as equilibrium heat, net equilibrium heat, integral entropy and surface potential have been calculated. The net isosteric heat, isosteric heat and differential entropy decreased with moisture content. The net equilibrium enthalpy, equilibrium enthalpy and integral entropy decreased with moisture content. The surface potential at four temperatures (35, 45, 55 and 65 °C) was estimated, and low temperature effect was reported.     

In vitro and in vivo propagation of Monotheca buxifolia (Falc.) A. DC. An economical medicinal plant

Monotheca buxifolia an economic and medicinal plant is restricted to limited areas due to deforestation, overgrazing, low regeneration, slow rate of germination, unsuccessful germination from cuttings and dormancy. Hence to cope with the issue of seed dormancy various invitro and invivo experiments were designed. The accidental breaking of seed through fungi (Rhizophus stolonifer) is also reported for the first time in current study. Different techniques used for breaking of dormancy are mechanical, chemical treatments i.e. (priming, scarification, stratification, ethanol, sulphuric acid, organic matter treatment, hot water) and tissue culture. Seeds were treated through various experiments in field, green house and laboratory. The scarified seeds placed on Murashige and Skoog medium for proliferation and callus production was 60% proliferation. Explants (Meristematic tissues) from field and tubes were inoculated on M. S (Murashige and Skoog medium) + 2, 4-D+ Kinetin. Meristematic tissues collected from field shows 10% callus formation and meristematic tissues from tubes show significant result (70% callus formation). Our study concludes that the best suitable media for callus preparation of Monotheca is Murashige and Skoog medium. Moreover, propagation of Monotheca via cutting is not possible. Development of callus explant from test tube was found to be more promising than field. Interestingly, Rhizophus stolonifer fungi can break dormancy of Monotheca seeds and found to promote growth significantly.     

Genetic polymorphism of flax Linum usitatissimum based on the use of molecular cytogenetic markers

Using a set of approaches based on the use of molecular cytogenetic markers (DAPI/C-banding, estimation of the total area of DAPI-positive regions in prophase nuclei, FISH with 26S and 5S rDNA probes) and the microsatellite (SSR-PCR) assay, we studied genomic polymorphism in 15 flax (Linum usitatissimum L.) varieties from different geographic regions belonging to three directions of selection (oil, fiber, and intermediate flax) and in the k-37 × Viking hybrid. All individual chromosomes have been identified in the karyotypes of these varieties on the basis of the patterns of differential DAPI/C-banding and the distribution of 26S and 5S rDNA, and idiograms of the chromosomes have been generated. Unlike the oil flax varieties, the chromosomes in the karyotypes of the fiber flax varieties have, as a rule, pericentromeric and telomeric DAPI-positive bands of smaller size, but contain larger intercalary regions. Two chromosome rearrangements (chromosome 3 inversions) were detected in the variety Luna and in the k-37 × Viking hybrid. In both these forms, no colocalization of 26S rDNA and 5S rDNA on the satellite chromosome was detected. The SSR assay with the use of 20 polymorphic pairs of primers revealed 22 polymorphic loci. Based on the SSR data, we analyzed genetic similarity of the flax forms studied and constructed a genetic similarity dendrogram. The genotypes studied here form three clusters. The oil varieties comprise an independent cluster. The genetically related fiber flax varieties Vita and Luna, as well as the landrace Lipinska XIII belonging to the intermediate type, proved to be closer to the oil varieties than the remaining fiber flax varieties. The results of the molecular chromosome analysis in the fiber and oil flax confirm their very close genetic similarity. In spite of this, the combined use of the chromosome and molecular markers has opened up unique possibilities for describing the genotypes of flax varieties and creating their genetic passports.     

秸秆隔层对盐碱土水盐运移及食葵光合特性的影响

在内蒙古河套灌区通过微区试验,研究了秸秆深埋(S)、上盖秸秆下埋秸秆(简称上秸下秸,S+S)、上盖地膜下埋秸秆(简称上膜下秸,P+S)和地膜覆盖(对照,CK)4种耕作措施对0-40 cm土层水盐运移及食葵光合特性的影响.结果表明:(1)不同措施对土壤水盐调控的效果与作用时期差异较大.P+S在整个生育期内土壤盐分含量和盐溶质浓度较低,控盐效果显著;S+S仅在苗期能保墒控盐,但控盐效果比P+S差,后期出现水减盐增现象,保墒控盐效果也不佳;S在整个生育期内土壤盐分含量和盐溶质浓度最高,控盐效果最差;CK在整个生育期内土壤水分含量变化不大,而盐分含量较高,控盐效果也不明显.(2)不同措施对土壤水盐运移调控程度的差异,导致食葵光合特性也有明显变化.与CK、S、S+S相比,P+S由于其较低的盐溶质浓度环境,明显改善了其光合特性,在苗期、蕾期和花期能提高净光合速率(Pn)和蒸腾速率(Tr),增加气孔导度(Gs),降低胞间CO2浓度(Ci),从而使其作物长势和干物质积累明显高于其它措施.综合试验结果,P+S是内蒙古河套灌区盐碱地改良中优选的控抑盐耕作措施.     

Effects of injecting cadherin gene dsRNA on growth and development in diamondback moth Plutella xylostella (Lep.: Plutellidae)

Two laboratory diamondback moth (DBM) strains were used to study the effects of injecting cadherin gene double‐stranded RNA (dsRNA) on the growth and development of Plutella xylostella (L.). Specifically, the susceptible strain named DBM.1Ac‐S and the low resistant strain DBM.1Ac‐R selected with Cry1Ac toxin were studied. The third larvae of the two strains were injected dsRNA of cadherin gene and their corresponding controls, DBM.1Ac‐RH and DBM.1Ac‐SH, were both injected diethypyrocarbonate (DEPC)‐treated water respectively. The basic biological properties such as death rate, hatching ratio, fecundity, weight of pupa and eclosion rate of the strains mentioned above were likewise studied. Meanwhile, the length and width of the egg and pupa were also measured. The results showed that the cadherin gene dsRNA injection resulted in a significant increase of the death rate and sex ratio. On the other hand, hatching ratio, fecundity, weight of pupa, eclosion rate and adult longevity for male and female of treatments decreased compared to their corresponding controls. As such, there was no significant difference on the length of egg and pupa in between treatments and the corresponding controls. However, their width increased inversely with their corresponding controls. Hence, the results suggest that cadherin gene dsRNA injection retarded the larval growth and development of P. xylostella. Also, these results can help reveal the function of cadherin gene through the RNA interference technique.     

Effects of the application of chemical additives to desiccated flax on retting

Summary Application of chemical additives to alter the rate of retting of desiccated flax stems was successful. Treatment with ethylenediaminetetra-acetic acid (EDTA) and urea increased the rate of retting. Increases, in the population of fungal colonisers were observed on urea-treated stems but not after EDTA treatment. Enhanced PG activities were detected in stems treated with EDTA and maimum PL and xylanase activities were detected in stems treated with urea. Urea treated stems produced relatively finer fibres compared to fibres from EDTA treated stems of controls.     

Factors Affecting Bacterial Adhesion on Selected Textile Fibres

In sectors like healthcare and hospitality, it has been realized that fabrics play a pivotal role in transfer of nosocomial infections. However, there is a major gap in drawing correlation between different fibre types and their interaction with microorganisms. Such information is important to formulate guidelines for textile materials for use in these sectors. In the current study, the adherence of four important bacteria, Staphylococcus aureus, Acinetobacter calcoaceticus, Escherichia coli, and Pseudomonas aeruginosa was studied on six different fibre types namely polyester, wool, polypropylene, viscose, silk and cotton. Among these fibres, viscose showed maximum adherence while silk fibres showed the least attachment of bacterial strains. Bacterial adhesion was correlated with the surface characteristics (surface charge, hydrophobicity etc.) of bacteria, and nanoroughness of fibres. Adhesion of these bacteria was tested on five hydrocarbons of different hydrophobicities. E. coli, the weakest biofilm producer, and with the highest surface energy and lowest hydrophobicity amongst the bacteria compared in the study, had the lowest load on all fibres. Scanning electron microscopy revealed non-uniform binding of gram-negative and gram-positive bacteria. Nanoroughness of fibres favored bacterial adhesion. The study showed correlation between surface properties and adherence of bacteria on fibres, with the results being of direct significance to medical and hospitality sectors.Electronic supplementary materialThe online version of this article (10.1007/s12088-020-00903-5) contains supplementary material, which is available to authorized users.     

Testing achene germinationof Potamogeton praelongus Wulfen

The goal of this work was to determine the best method of breaking the achene dormancy in Potamogeton praelongus Wulfen. The ways of breaking achene dormancy studied in this experiment included methods of achene storage, stratification, UVA radiation, anaerobic conditions, mechanical disruption of achenes?outer layers and their chemical disruption by NaClO. Nine different treatments of achenes were combined with two methods of achene storage. Particular achene treatments and storage conditions were proven to have a significant impact on breaking dormancy. Although the highest germination rate (83.3%) was achieved when the dormancy was broken chemically by long effect of 100% concentrations of Savo detergent (containing 5% NaClO), the growth of the sprouts was subsequently inhibited due to toxic effects of Savo. Thus the most successful treatment was based on changing temperature, e.g. 2.5 months of cold storage followed by 14 days at room temperature (germination rate 32.7%). This treatment was also most similar to the natural process. Germinated achenes were also found in Petri dishes exposed to UVA radiation, anaerobic conditions and chemical disruption of the outer layers. Results of these treatments were influenced by the storage method.     

Immobilization of Bacillus licheniformis α-amylase onto reactive polymer films

Alpha-amylase was covalently immobilized onto maleic anhydride copolymer films preserving activity. The initial activity of the immobilized layers strongly depended on the immobilization solution, and on the physicochemical properties of the copolymer film. Higher enzyme loading (quantified by amino acid analysis using HPLC) and activity (measured by following starch hydrolysis) were attainable onto hydrophilic, highly swelling 3-D poly(ethylene-alt-maleic anhydride) (PEMA) copolymer films, while immobilization onto hydrophobic poly(octadecene-alt-maleic anhydride) (POMA) copolymer films resulted in low content enzyme layers and lower activity. No significant activity was lost upon dehydration/re-hydration or storage of enzyme containing PEMA copolymer layers in deionised water for up to 48 h. In contrast, α-amylase decorated POMA films suffered a significant activity loss under those conditions. The distinct behaviours may be attributed to the different intrinsic physicochemical properties of the copolymer films. The compact, hydrophobic POMA films possibly favours hydrophobic interactions between the hydrophobic moieties of the protein and the surface, which may result in conformational changes, and consequent loss of activity. Surprisingly, residual activity was found after harsh treatments of active α-amylase PEMA based layers revealing that immobilization onto the hydrophilic polymer films improved the stability of the enzyme.     

Site-specific interaction of ATPase-pumped protons with photosystem II in chloroplast thylakoid membranes

The chloroplast thylakoid ATPase proton pump-driven H+ accumulation in the dark was compared to the light-dependent proton pump driven by either photosystem II or I, in regard to the effects of the resultant acidity on chemical modification reactions. The assays used to detect the acidity effects were: (a)the incorporation of [3H]-acetic anhydride into membrane protein -NH2 groups, and (b) the effect of a certain level of that chemical modification on inhibition of photosystem II water oxidation activity. Based on labeling data with [3H]-acetic anhydride, 20-30 nmol.(mg chl)-1 of -NH3+ groups appear to be metastable in the dark in untreated membranes. The term metastable is used because proton leak-inducing treatments in the dark lead to about 20-30 nmol . (mg chl)-1 increase in acetic anhydride labeling probably due to reaction with the -NH2 form of amine groups. Addition of low levels of uncoupler or a brief thermal treatment caused a loss of protons from the membrane equivalent to the increase in acetic anhydride derivatization. The increase in acetic anhydride derivatization caused inhibition of water oxidation activity. Using thermally sensitized membranes, photosystem II but not photosystem I electron transport (each giving a steady-state proton accumulation of about 50 nmol H+ . (mg chl)-1 restored the lower level of acetic anhydride reactivity as in previous results (Baker et al., 1981). In dark-maintained, thermally treated membranes, ATPase activity, i.e., the proton pump associated with it, also restored the lower level of acetic anhydride labeling, and again acetic anhydride no longer inhibited water oxidation. Because photosystem I activity did not elicit this type of response to acetic anhydride, there appears to be a pathway for ATPase pumped protons which allows them to reach a restricted domain, perhaps intramembrane, common with the photosystem II water oxidation mechanism and unavailable to protons pumped by photosystem I. The membrane structure(s) which determines this site specificity is not yet understood.