Dew Retting Research Articles

Metaproteomics identifies key cell wall degrading enzymes and proteins potentially related to inter-field variability in fiber quality during flax dew retting

In this study, metaproteomics and biochemical analyses were used to identify for the first time specific proteins and associated micro-organisms responsible for cell wall degrading enzyme activity during dew retting of flax in two adjacent fields in northern France. This approach identified 6032 non-redundant proteins present at 4 key retting stages (R0/day 1, R2/day 6, R4/day 13, and R7/day 25), of which 75 contained CAZy (Carbohydrate Active Enzyme) motifs belonging to 31 different families from all 5 CAZy classes. 19 families were putatively related to the degradation of different plant cell wall polymers including lignin (AA1), pectins (CE13, CE8, PL1, PL3, GH28, GH35), hemicellulose (GH2, GH10, GH26, GH35, GH55, GH3, GH5, GH17) and cellulose (GH5, GH7, GH3, GH94, AA3). Taxonomy of identified proteins indicated that 85 % come from bacteria, 13 % from fungi, and 2 % from plants; however, ∼60 % of CAZymes involved in the degradation of plant wall polymers are of fungal origin. Although 88 % of total proteins and almost 65 % of cell wall degrading CAZymes were similar between the two investigated fields, certain differences in the abundance and dynamics of certain CAZymes might be related to observed inter-field variability in cell wall degrading enzyme activities, stem/fiber yield and industrial qualities of fibers harvested from the two fields. Overall, these results highlight the interest of using metaproteomics for improving our biological understanding of how retting impacts fiber quality. In addition, the identification of several new bacterial and fungal species in this study demonstrates that such an approach is also extremely powerful for generating novel taxonomic data.

The Influence of Dew Retting on the Mechanical Properties of Single Flax Fibers Measured Using Micromechanical and Nanomechanical Approaches

The mechanical properties of single flax fibers are characterized here as a function of dew retting. The fibers are measured using micromechanical and nanomechanical techniques over a large retting period (91 days). Damage-free single flax fibers in various stages of dew retting were manually extracted from retted flax plant stems. The flexural modulus and strength of the flax fibers were determined using micromechanical methods. The effective modulus of the outer surface of the single fibers was measured using AFM-based nanoindentation. The micromechanical methods revealed that the flexural modulus and strength of the manually extracted single fibers does not vary significantly as the retting progresses. The micromechanical methods revealed two distinct values of flexural strength in the fibers attributed to different failure modes. The values of these strengths do not vary significantly with retting or over-retting. The nanomechanical methods revealed that the effective modulus of the outer surface of the single fibers does evolve with retting. The physical/chemical origin of these observations remains to be established and could be the objective of future work.

Water retting process with hemp pre-treatment: effect on the enzymatic activities and microbial populations dynamic

Proper retting process of hemp stems, in which efficient separation of cellulose fiber from the rest of the stem is promoted by indigenous microorganisms able to degrade pectin, is essential for fiber production and quality. This research aimed to investigate the effect of a pre-treatment dew retting in field of hemp stalks on the pectinolytic enzymatic activity and microbiota dynamic during lab-scale water retting process. A strong increase in the pectinase activity as well as in the aerobic and anaerobic pectinolytic concentration was observed from 14 to 21 days, especially using hemp stalks that were not subjected to a pre-retting treatment on field (WRF0 0.690 ± 0.05 U/mL). Results revealed that the microbial diversity significantly varied over time during the water retting and the development of microbiota characterizing the water retting of hemp stalks of different biosystems used in this study was affected by pre-treatment conditions in the field and water retting process and by an interaction between the two methods. Although at the beginning of the experiment a high biodiversity was recorded in all biosystems, the water retting led to a selection of microbial populations in function of the time of pre-treatment in field, especially in bacterial populations. The use of hemp stems did not subject to a field pre-treatment seems to help the development of a homogeneous and specific pectinolytic microbiota with a higher enzymatic activity in respect to samples exposed to uncontrolled environmental conditions for 10, 20, or 30 days before the water retting process.Key points• Microbial diversity significantly varied over time during water retting.• Water retting microbiota was affected by dew pre-treatment in the field.• Retting of no pretreated hemp allows the development of specific microbiota with high enzymatic activity.

The Quantity and Quality of Flax and Hemp Fibers Obtained Using the Osmotic, Water-, and Dew-Retting Processes

This study presents the quantity and quality of flax (Linum usitatissimum L.) and hemp (Cannabis sativa L.) fibers obtained depending on the fiber extraction method. The extraction methods used in this study were osmotic degumming, dew retting, and water retting. The degummed straw was analyzed for fiber content, while the metrological, chemical, and physical properties were determined for the fibers obtained. It was shown that these properties change based on the method of fiber extraction used. The highest fiber content in the straw was obtained using the osmotic degumming method. These fibers are characterized by a light color, no unpleasant odor, low linear mass, good tenacity, lowest hygroscopicity, and reduced flammability compared to fibers obtained via the dew and water retting of straw.

Effect of enzyme retting conditions on bast bundle differentiation and mechanical properties of flax technical fibers

Compared to conventional dew retting, enzymatic retting has the potential to control fiber extraction process and produce high quality plant fibers for industrial scale composite applications where low Family videovariation in properties are desired. While most studies depend upon retting duration and fiber fineness as measures for effective retting degree, in this study we report the effect of enzyme concentration and enzyme retting duration on the flax bast-woody core bond strength and resulting technical fiber fineness. Fiber peel tests and microscopy coupled with statistical analysis showed that while only retting duration has significantly effect on fiber fineness, the bond strength between the bast-woody core interphase is significantly affected by both enzyme concentration and time. Single fiber tensile tests were conducted on flax fibers from different retting conditions at 10 mm and 30 mm gauge lengths. Fibers extracted from a high degree of enzymatic retting performed well at 10 mm gauge length but showed lower tensile strength at 30 mm gauge length, indicating over-retting. These findings can guide optimizing the enzyme retting process conditions at industrial scale for improved fiber properties with reduced variability.

How the interplay between harvest time and climatic conditions drives the dynamics of hemp (Cannabis sativa L.) field retting

Dew retting, the selective biodegradation of industrial hemp (Cannabis sativa L.) stems after harvest, is a key field process for plant fiber use. The stage of maturity of the crop and the weather conditions during the subsequent dew retting process differ with hemp harvest time, which depends on the hemp valorization scenario. In this work, the aim was to investigate and rank the important factors that drive hemp retting, such as hemp harvest date, weather during retting, soil type under hemp mulch, and their interactions under agricultural field conditions. To this end, an experimental field trial was set up in the northeastern area of France (Champagne region), with two hemp harvest scenarios and two types of soil common to the agricultural area. Physicochemical hemp characteristics and climatic conditions were dynamically monitored during the retting periods. Dynamics of stem characteristics determined at the biomass level (dry matter loss) and the outer tissue level (surface analysis, chemical and thermal analysis) showed that the kinetics of retting followed similar patterns regardless of soil type for both harvest date scenarios. The kinetics were strongly and linearly related to air temperature, expressed as the number of normalized days at 15 °C, and to cumulative radiation during retting periods. The cumulative amounts of rain and dew explained the kinetics less than temperature and radiation, regardless of the retting scenario considered. The strong relationship observed between colorimetry and infrared spectroscopic data for characterizing the retting progress for both harvest scenarios paves the way for the development of tools to monitor changes in hemp stem quality.

Assessing the promoting effect of compound microbial agents on flax dew retting: Based on the relationship between metabolites and core genera

In this study, 16S rRNA sequencing and GC–MS (gas chromatography–mass spectrometry) techniques were employed to examine the relationship between bacterial succession and metabolite alterations during the dew retting process of flax. The results indicated that the addition of compound microbial agents may affect the production and transformation of metabolites by re-establishing bacterial communities and promoting the degradation of pectic substances and the release of metabolites, and the best retting effect was achieved under the combined addition (BA). In addition, Chryseobacterium, Bacillus, and Pseudoonas were closely associated with the production of fatty acids and alcohols; the addition of compound microbial agents increased the content of critical metabolites while decreasing the environmental pollutant bis(2-ethylhexyl) phthalate. In summary, the addition of compound microbial agents can positively regulate the retting process of flax, shorten the retting cycle, improve the quality of flax fibre, and reduce the pollution of the environment.

IMPACT OF ALKALINE TREATMENT ON THE CONSTITUENTS, STRENGTH AND MORPHOLOGICAL CHARACTERISTICS OF BANANA FIBER

The readily availability of natural fibers have made them to be less expensive compared to the synthetic fibers. Hence, highest substitute for synthetic fibers in composites development today is natural fibers. In this research, banana fiber was extracted by dew retting and treated with alkaline for surface modification and possibly strengthening. Both treated and untreated fibers were tested with universal tensile testing machine and examined their surface morphology with scanning electron microscopy. The banana fiber's ultimate tensile strength (UTS) was assessed as a function of fiber diameter, test length and testing speed. It was observed from the results that chemical treatment improved the tensile strength of the fiber while surface morphology was noticed to be rough due to the removal of some fiber constituents. Hence, it was discovered that alkaline treatment improved the fiber condition, thus, making the fiber a suitable substitute for synthetic fibers in composite development

Effects of extraction techniques on textile properties of William banana peduncle fibers

In this research work, the effect of extraction methods on the physical (morphology, density, length, apparent diameter, and color) and mechanical (tensile and bending KAWABATA) properties of the William banana peduncle fibers were examined. Among the methods used to carry out those tests, can be cited; the extraction tests using water retting (WR), dew retting (DR), and rolling by mechanical extraction (ME). The mechanical tests were carried out using TEXTECHNO Vibromat ME (measurement of the vibration frequency of the fiber), tensile test (MTS 20/M), and a Bending KAWABATA KES-FB2-SH test. To analyze the microstructure of the longitudinal plane of William banana peduncle, Scanning Electron Microscopy (SEM) mapping was used. The results showed that, water retting, gave a high yield (42.55%) compared to fibers extracted by rolling (23.40%). The different methods of extraction by retting lead to a reduction of about 35% in the apparent diameter of the fibers compared to the fibers obtained mechanically. When studying the colors of the surfaces of the fiber, the results presented the fact that the fibers extracted by rolling (ME) were darker than those retted in water or dew (WR and DR). However, the retted fibers were redder and yellower compared to the fibers passed through a rolling mill. SEM mapping was a result of strips of flat fiber bundles, followed by the brittle fracture surface regardless of the extraction method used. water retted fibres are longer than those extracted by rolling. There was a high uniformity index (UI) value for WR (70. 89%), which showed that these fiber bundles were more uniform in length compared to the two other methods (66.4% for DR and 64.28% for ME). The density of the William banana peduncle was not very sensitive to the extraction method. Significant differences were revealed for the specific breaking strength, initial modulus, and elongation at break depending on the extraction method. The Kawabata bending test showed the fact that fibers extracted by rolling were stiffer (1.63 mNmm2/tex2) compared to retting method fibers (0.51 mNmm2/tex2 for WR and 0.73 mNmm2/tex2 for DR). There is a possibility of using William banana fiber for textile applications in view of the tensile and bending properties obtained.

Development of 100% Linseed Flax Yarns with Improved Mechanical Properties and Durability for Geotextiles Applications

Due to the ever-growing demand for bast fibres for technical and garment textiles, complementary sources to textile flax, whose cultivation in western Europe cannot really be extended, need to be proposed. In this study, the interest in harvesting and processing linseed flax straw is studied for geotextile applications. The main critical stages of fibre-to-yarn production for geotextiles were investigated. Different dew retting levels as well as different all-fibre extraction processes were investigated to achieve this objective. It was demonstrated that the fibres extracted from linseed flax stems subjected to 12 weeks of dew retting using breaking rollers, thresher and a breaking card exhibited the most suitable morphological and mechanical properties. The optimal fibres were converted into 100% linseed flax yarns using a flyer spinning machine, and the mechanical properties as well as the biodegradability of the linseed yarns were evaluated to understand their potential as geotextiles. These linseed flax yarns were further coated with linseed oil or chitosan to enhance their durability. It was observed that the linseed oil coating better preserved the yarn’s integrity and mechanical properties over time, and it permitted doubling their service life potential.

Effect of Surface Modification of Himalayan Nettle Fiber and Characterization of the Morphology, Physical and Mechanical Properties

Abstract The process of retting bast fiber plants for the production of long fiber has presented major challenges. Water retting, dew retting, chemical extraction, and micro-organism (fungi, enzymes) techniques were applied to the extraction of natural fibers. The two nettle samples were extracted with water retting for 14 days and dew retting for 4 weeks. This research investigated the effects on the traditional retting process of nettle fiber by fungi and bacteria formation in lignocellulosic. The latter biological extraction methods successfully degraded the lignin and pectin materials of the fiber and increases the cellulose content. These extraction methods produced high quality fiber and tensile strength at a low cost. This study determined the chemical, physical, and mechanical characteristics such as fiber cellulose, non-cellulosic content, tensile strength, tenacity, and elongation break to see how treatments affected them. The treated fiber surface morphology was characterized using scanning electron microscopy. To evaluate functional group alterations, Fourier-transform infrared spectroscopy was used on the fiber specimen.

Hemp Fibre Properties and Processing Target Textile: A Review.

Over the last several decades, Cannabis sativa L. has become one of the most fashionable plants. To use the hemp potential for the development of a sustainable textile bio-product sector, it is necessary to learn about the effect of the processes creating hemp’s value chain on fibre properties. This review presents a multi-perspective approach to industrial hemp as a resource delivering textile fibres. This article extensively explores the current development of hemp fibre processes including methods of fibre extraction and processing and comprehensive fibre characteristics to indicate the challenges and opportunities regarding Cannabis sativa L. Presented statistics prove the increasing interest worldwide in hemp raw material and hemp-based bio-products. This article discusses the most relevant findings in terms of the effect of the retting processes on the composition of chemical fibres resulting in specific fibre properties. Methods of fibre extraction include dew retting, water retting, osmotic degumming, enzymatic retting, steam explosion and mechanical decortication to decompose pectin, lignin and hemicellulose to remove them from the stem with varying efficiency. This determines further processes and proves the diversity of ways to produce yarn by employing different spinning systems such as linen spinning, cotton and wool spinning technology with or without the use of the decortication process. The aim of this study is to provide knowledge for better understanding of the textile aspects of hemp fibres and their relationship to applied technological processes.

On the origin of bast fiber dislocations in flax

Bast fibers of many fiber crops are valuable raw material for diverse applications. The isolated from flax stem technical fibers demonstrate numerous defects that are considered to accumulate both during plant growth and various steps of crop processing. We have performed quantitative estimation of dislocations in flax bast fibers within stems of developing plants and at different stages of stem processing, including drying in sheaves, dew retting, scutching and hackling. Scanning electron microscopy revealed no dislocations in fibers within the stem. Numerous defects appeared after scutching in ex-planta fibers and increased in frequency during subsequent technological step. We propose the disturbance of flax stem integrity and the mechanical treatments acting directly on fibers to serve the main factors of fiber deformation emergence.

Continuous Mechanical Extraction of Fibres from Linseed Flax Straw for Subsequent Geotextile Applications

Linseed flax is a multipurpose crop. It is cultivated for its seeds and particularly for its oil. The main contributors for this crop are Canada, France and Belgium. In general, straws of linseed flax are buried in the fields or burnt. However, these solutions are not good practices for the environment and from an economical point of view. In this study, straws of linseed flax (six batches in total) with different dew retting durations and harvesting techniques were studied to possibly use them for producing innovative geotextiles. Two different fibre extraction processes were investigated. A first process (A) involved horizontal breaker rollers and then a breaking card. A second one (B) consisted in using vertical breaker rollers, and an “all fibre” extraction device (fibre opener) followed by sieving. The chemical composition of fibres in parietal constituents appeared to be globally equivalent to the one of textile flax with a pectic content decreasing as a function of the dew retting duration. This contributed to an increase in the cellulose content. The fibre content was situated in a range from 29% to 33%, which corresponds to a good yield for linseed flax fibre. The level of purity can reach values of up to 90% for method A (without extra-sieving) and 96% for method B (with extra-sieving), and the length of the fibres (larger for method A than for method B) and their tensile properties make them suitable for structural geotextile yarn manufacturing.

Extraction, Treatment and Applications of Natural Fibers for Bio-Composites – A Critical Review

Abstract Nowadays, sustainable and eco-friendly products are gaining more attention in various engineering industries owing to their considerable strength-to-weight ratio, abundant availability, and recyclability. The properties of biofibers depend on the cultivation method, environmental conditions, and extraction method. Biofibers are hauled out by dew retting, water retting, and mechanical decortication methods. The properties of natural fiber–reinforced composites can be enhanced by proper physical and chemical treatments. The aim of this study is to propose a complete evaluation of the different extraction methods applied on natural fibers. Various physical and chemical treatment methods were used to ascertain the properties of optimized natural fiber-reinforced composites for various industrial applications. The key findings derived from various existing data and the chemical treatment results of the biofiber-reinforced composite are specifically highlighted with critical assessment. The properties and use of natural fiber-reinforced composites in the various fields of applications have made them candidates of choice over synthetic petroleum–based fibers.

Influence of structural physiognomies of pawpaw fiber–glass fiber hybrid–based green composites on mechanical properties and biodegradation potential of epoxy composites

The demand for durable and sustainable eco-friendly materials in recent times has caused many researchers to consider the use of plant fibers in composite development. In this research, the suitability of treated pawpaw fiber as a substitute for glass fiber was considered. The pawpaw fiber was extracted from the plant stem by dew retting and treated before been incorporated into the epoxy matrix. Two distinct fiber structures in linear and network forms were identified, separated, and used for the development of the composites. The composites were produced by incorporating a fixed amount of pawpaw fiber with a varied amount of glass fiber within 3–15 wt% in epoxy-based polymer matrix after which mechanical and biodegradation tests were carried out on the developed samples. Fractured surface morphology was also observed using a scanning electron microscope. The results revealed that the fiber structures influence the properties of the material. While mechanical properties were mostly enhanced by treated linear structure pawpaw fiber, biodegradation was highly promoted by treated network structure pawpaw fiber. Tensile (except for strain), hardness, and flexural properties were enhanced by the linear-structured treated pawpaw fiber, while biodegradability, impact, and tensile strain were improved by the network-structured treated pawpaw fiber compared to the control sample.

Exploring the dew retting feasibility of hemp in very contrasting European environments: Influence on the tensile mechanical properties of fibres and composites

Retting of fibrous plants such as flax is an essential step in the extraction of fibre bundles and their transformation into textiles and reinforcement fabrics for use in garments and composites. Dew-retting is traditionally performed from Northwest France to the Netherlands, as the climate is highly favourable for this process. Hemp is a plant that can be grown almost all over Europe with a low environmental impact. A retting step is also required to facilitate the separation of the hemp fibres before their transformation into textiles for garments or for 1D to 3D reinforcement composites, which requires thoroughly separated fibres. Dew-retting is currently used in flax production zones. The present work demonstrates that dew retting can be conducted under different climates on different soils, from dry Mediterranean environments up to the cooler regions of eastern France. If the ternary combination of moisture, temperature and solar radiation is appropriate, field retting (dew-retting) can be as short as about three weeks. In less favourable conditions, such as in dryer areas or when retting is performed late in the season after seed maturity (cooler temperatures), it lasts longer, but it can reach suitable levels. When conducted with care and with proper monitoring of the retting level, the dew-retting process does impact neither the tensile properties of elementary hemp fibres (by degrading crystalline cellulose I) nor the tensile properties of unidirectional and injected composite materials. Consequently, if extracted with a suitable process such as scutching and hackling, fibres suitable for load-bearing composites can be produced from dew-retted hemp stems produced in a wide range of climates and locations, therefore not limited to the conventional “dew retting zone” of flax production areas.

Quality optimization of flax fibre through durational management of water retting technology under sub-tropical climate

The ascendancy of flax fibre strongly depends on the duration and process of its retting. In sub-tropical areas, warm and dry season quickly following the cold flax growing season does not allow dew retting of flax. Hence, development of suitable retting technology is utmost need under such climate. Therefore, an experiment was designed with seven tank-retting durational treatments [0 day (unretted), 1 day, 2 days, 4 days, 6 days, 8 days and 10 days] to find out the best retting period. The data revealed that the rate of weight loss was augmented upto fourth day of retting, while, rate of pectin loss was the highest on the second day of retting. Overall, it was also observed that the best quality flax-fibre was obtained with tank-water retting of 4–6 days. Retting of less than 4 days resulted in lower degumming, higher non-cellulosic material, while, more than 6 days caused over retting owing to poor quality fibre.

A review of natural fiber composites: Extraction methods, chemical treatments and applications

Developing sustainable products from renewable materials represents a large dispute in the last few years. Bio-fibers obtained by retting process from plants are receiving more attention from material experts owing to their sustainability, bio degradability, renewability and recyclability nature. The physical and mechanical properties of natural fibers depend on the cultivation method, environmental condition, extraction method and microfibrillar angle. Plant fibers are separated either by dew retting, water retting and/or mechanical decortications method. The properties of natural fiber reinforced composites could be enhanced by suitable chemical treatment processes. This literature survey proposes an in depth review of the extraction methods, chemical treatments and applications for natural fiber composites. We recapitulate the conclusion from the various recent literatures and the chemical treatment outcomes on the mechanical performance of the natural fibers are being highlighted.

Multiscale modeling of microbial degradation of outer tissues of fiber-crop stems during the dew retting process

Dew retting of fiber crops, such as hemp or flax, in the field after harvest promotes the microbial biodegradation of the tissues surrounding cellulosic fibers, which helps preserve the quality of fibers during their extraction and valorization for industry. This bioprocess is currently the bottleneck for plant fiber valorization because it is empirically managed and its controlling factors have not been properly quantified. A novel multiscale model representing tissue and polymer biodegradation was developed to simulate microbial growth on the stem during retting. The model was evaluated against experimental hemp retting data. It consistently simulated the mass loss of eight plant polymers belonging to two tissues of the stem outer layer, i.e., parenchyma and fiber bundles. Microbial growth was modeled by Monod equations and modulated by the functions of temperature and moisture. This work provides a tool for gaining more insights into microorganism behavior during retting under local climate conditions.