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1.
Summary The bacteria present on samples of desiccated flax stems were Bacillus mycoides, B. subtilis, Erwinia carotovora, Pseudomonas fluorescens, P. putida and Micrococcus sp. and the fungi present were Cladosporium herbarum, Fusarium culmorum, Botrytis cineria, Epicoccum nigrum and yeast. When inoculated on autoclaved stems or in liquid culture, B. subtilis produced mainly pectin-lyase and xylanase. However, only pectin-lyase was detected in significant levels in autoclaved stem sections or in liquid cultures inoculated with E. carotovora. Enhanced pectin-lyase and xylanase levels were detected in field-retted stems sprayed with B. subtilis compared with enzyme levels in stems sprayed with E. carotovora or the control stem tissues. Increases in the fungal population coincided with a reduction in the bacterial population on treated stems at the later part of retting. Enhanced retting was observed in stems sprayed with B. subtilis and consequently the stems produced finer fibres than fibres from E. carotovora-sprayed or control stems.  相似文献   

2.
Seven strains of filamentous fungi and one yeast were isolated from flax that was dew retted in the United States. These filamentous fungi were subcultured to purity and identified, and six appear not to have been reported earlier as isolates from dew-retted flax. Five of the purified U.S. strains, two fungi isolated from flax that was dew retted in Europe, and a laboratory culture of Aspergillus sojae were tested for their ability to ret flax stems. The monocultures were evaluated for the degree of retting, fiber strength, dry weight loss, and tactile response (i.e., feel of softness) as reflected in the retted fiber. Structural modifications of representative samples of the retted flax were assessed by scanning electron microscopy. All of the filamentous fungi were able to carry out some retting, whereas the isolated yeast could not. All organisms produced pectinases when they were cultivated in shake flasks on ball-milled flax as the sole carbon source. Some fungi also produced cellulases, mannanases, and xylanases. Rhizomucor pusillus and Fusarium lateritium were noteworthy as retting organisms by their high level of pectinase activity, ability to attack noncellulosic cell types without attacking cellulose, capacity to penetrate the cuticular surface of the stem, and efficient fiber release from the core. The results indicated that these organisms deserve further study as potential organisms for retting of bast fibers in industrial applications.  相似文献   

3.
A wide range of concentrations of ethylenediaminetetra acetic acid (EDTA) was tested as a retting agent at a range of temperatures, pHs and stem: liquor ratios. Treatment of stems at 2 and 3 g/litre at 40 °C in a liquor ratio of 1:10 at pH 11 produced the finest and strongest fibre. Dried-green stem retted slightly better than the glyphosate-desiccated stem and after multiple retting with EDTA, Trilon TB and diethyltriaminepenta acetic acid (DTPA), the dried-green stem produced the finest fibre. Trilon TB and DTPA retted better than EDTA and produced a high yield of fibres. The fluidity of fibres scutched from the dried-green stem was lower than the fluidity of the fibres from glyphosate-desiccated stem.  相似文献   

4.
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.  相似文献   

5.
Flax dew-retting is widely adopted in most flax-growing countries, but it does not represent a practical solution where dry weather conditions occur after harvest. A study of the local microbiological aspects was undertaken as a contribution to improve field-retting of flax under southern European climates. Fungi were isolated from soil and dew-retted flax in northern Italy, and 23 representative strains were chosen to test their ability to ret flax stems. Experiments were performed in vitro on flax stem pieces artificially inoculated with single fungal strains. Retting degree was assessed with a mechanical test, to evaluate the ease with which the bast was detached from the wood core, and by the analysis of the residual fibre pectins using uronic acid. Uronic acid dosage provided a better differentiation of the strains than the mechanical test. There was a large variability in retting ability among the species assayed and even among strains of the same species. The best results were obtained with all Aspergillus and Penicillium strains, while Mucor and Rhizopus strains showed a variable retting ability. Fusarium, Trichoderma strains and Epicoccum nigrum had the poorest retting abilities among all the fungal strains assayed.  相似文献   

6.
Samples of barley straw, chopped to 5 cm nominal particle length, were treated with 7.5 g NaOH in 120 ml solution per 100 g dry matter (DM) and either dried immediately after treatment or stored at ?15°C for 24 days prior to drying. The samples were either dried at 100°C in a forced-draught oven, or were freeze-dried. For the samples dried immediately after treatment, incubation in vitro commenced 40 h after treatment. Digestibility in vitro was higher for oven-dried than for freeze-dried samples, particularly when the samples were incubated 40 h after treatment with alkali. Digestibility was also higher for samples which were stored prior to being dried than for those dried directly after treatment with alkali. This suggests that the reaction of alkali with straw continued during the storage of undried material at ?15°C.  相似文献   

7.
Sowing density and harvest time are considered important crop management factors influencing fibre quantity and quality in hemp (Cannabis sativa). We investigated whether the effects of these factors are essentially different or that both factors affect stem weight and thereby total and long‐fibre content. The effects of all combinations of three sowing densities and three harvest times were studied for six different stem parts. Almost 500 samples consisting of stem parts from 50 plants and with a length of 50 cm were tested. Fibres were extracted by a controlled warm‐water retting procedure, followed by breaking and scutching. The initial sample weight was fractionated into retting losses, wood, tow and long fibre. In both Italy and the Netherlands, crops were successfully established with different stem densities (99–283 m?2), plant heights (146–211 cm) and stem diameters (4.5–8.4 mm) at harvest. Stem dry matter yields (6.8–11.7 Mg ha?1) increased with a delay in harvest time but were not affected by sowing density. Retting loss percentages were lower in lower stem parts and decreased with later harvest because maturation was associated with increasing amounts of fibre and wood. Within a certain stem part, however, the absolute retting losses were constant with harvest time. Multiple linear regression analyses showed that the amount of fibre in a hemp stem is almost completely determined by the weight and the position of that stem part. When the plant grows, the increase in dry matter is split up into fibres and wood in a fixed way. This total fibre/wood ratio was highest in the middle part of the stem and lower towards both bottom and top. Sowing density and harvest time effects were indirect through stem weight. The long‐fibre weight per stem increased with the total fibre weight and hence with stem weight. Stem weight increased with harvest time; as harvest time did not affect plant density, the highest long‐fibre yields were obtained at the last harvest time. The long fibre/total fibre ratio was lowest in the bottom 5 cm of the stems but similar for all other parts. Sowing density and harvest time effects again were indirect. Fibre percentages in retted hemp decreased with increasing stem weights towards a level that is presumably a variety characteristic. The dry matter increase between harvests, however, is much more important with respect to total and long‐fibre yield.  相似文献   

8.
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.  相似文献   

9.
Legume root-nodules, dried at oven temperature (70°C for 48 h) were suitable for Rhizobium strain identification by immunofluorescence and agglutination. The fluorescence of bacteroids of R. japonicum, R. leguminosarum, R. meliloti, R. phaseoli , and Rhizobium spp. from oven-dried nodules was the same as those from frozen, desiccated, or nodules dried at room temperature (28°C). Oven-dried nodules did not require further steaming for agglutination. Bacteroid agglutinations gave 2–16 fold lower titres than those of the cultured cells. Fresh and oven-dried soybean rhizobia from a mixed inoculation gave exactly the same results when identified by immunofluorescence or agglutination.  相似文献   

10.
Greater numbers of fungi were isolated from stems of flax following treatment with the herbicide glyphosate than from untreated stems although there was also a general increase in numbers with time. The fungal genera isolated were the same from both treated and untreated plants, the most common being Cladosporium, Aureobasidium, Epicoccum and Botrytis with Cladosporium being predominant. Populations of bacteria were generally not enhanced after glyphosate treatment. Partial dew-retting of crops resulted in the reduction in numbers of Cladosporium compared with conventionally-treated flax. The increase in numbers of fungi was associated with an increase in retting. Overretting also occurred, particularly in discrete pale areas on the stem. These were associated with colonisation by Botrytis cinerea and the tensile strength of fibres from these areas was 15 times weaker than from surrounding darker areas of the stem. Light microscopy showed death of cells after glyphosate application, followed by invasion and degradation of the epidermis and cortex by fungi and other microorganisms. Fibre bundles were partially dissociated but the individual fibres remained largely intact as did the xylem and medulla.  相似文献   

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