A hand tool to assess the strength of flax and other fibrous materials

Flax fibres may become weakened during retting. A simple tool is described which can be used to assess their tensile strength. Other applications are also suggested.     

Study on microbe retting of kenaf fiber

Retting is the predominant problem in the application of kenaf fiber in high-grade products. While the traditional retting method is water retting, that is, the harvested bast kenaf is immersed in natural water (rivers or tanks) in which indigenous bacteria colonize noncellulosic materials in an anaerobic process resulting in severe environmental problems and low-grade fiber, therefore it is inevitable to seek for a pollution-free or little-pollution retting method. With the more application of biotechnology in textile industry, the more biology-treatments have been researched recently. So microbe retting was employed in this work. The fungus strain was isolated from the river in which kenaf fiber was retted, then microbe retting was performed with this fungus. Substrate species, the initial pH of the culture medium, cultivation temperature, retting time and inoculum size are involved in the experiments and the evaluation of retting is based on the residual gum content in retted kenaf fiber. As a result, the removal of pectin in microbe retting of kenaf is 91.31% under the optimal retting conditions. In addition, the effective retting fungus is also observed with microscope as one kind of filamentous epiphyte.     

亚麻脱胶菌种的选育及脱胶过程的初步研究

从沤麻主生物期的水中分离产果胶酶的菌株经初筛、复筛获得了三株专性厌氧细菌,初步鉴定为费氏芽孢杆菌,对其亚麻脱胶性能进行了初步研究,确定人工加菌沤麻的最适工艺条件为：加菌量2％,加菌时间：沤麻进入主生物期零时,菌株A优于其它菌株．结果表明：采用上述工艺进行沤麻实验,可缩短沤麻时间30％,并可提高麻纤维质量。     

The retting of flax after preservation with sulphur dioxide

Experiments were carried out to compare the retting of moist flax preserved with sulphur dioxide with that of green dried flax, using whole straw samples. When retted in water at either a constant 20°C or 28°C dried flax was fully retted after 15 and 10 days respectively whereas the sulphur dioxide treated flax (20 g sulphur dioxide kg“¹ flax DM) had undergone almost no retting after 20 days at 20dC or 10 days at 28°C. Pre-soaking the treated flax for 24 h in water and changing the acidified water, raised the pH of the retting liquor to a more normal value but did not significantly increase the rate of retting. Addition of the pectinase enzyme preparation ‘Flaxzyme’ to retting liquor at the rate of either 1.5 g kg^-1 or 3.0 g kg^-1 water, and at a constant temperature of 20°C, substantially increased the rate of retting of both sulphur dioxide treated and dried flax. Optimum degree of retting was achieved at 24 h with the treated flax and at 97 h with the dried flax. Pre-rinsing of the sulphur dioxide treated straw only served to reduce the rate of retting. It was concluded that natural water retting of sulphur dioxide treated flax is retarded by the presence of acidic residues of sulphur dioxide, while enzyme retting is enhanced by these. In further smaller scale experiments using bundles of cut flax straw Flaxzyme was added at concentrations ranging from 0–8.0 ml litre ¹ to containers containing flax in water at ratios from 1:10 to 1: 600 flax:water and the producion of galacturonic acid was used as an indicator of retting progress. Retting took place more rapidly at higher flax to water ratios for a given enzyme concentration. This effect was attributed to the lower pH of higher flax to water ratios which created pH conditions closer to the pH optimum for the retting enzymes. When enzyme retting was compared at a range of buffered pH's the optimum was pH 4.0. At a buffered pH of 4.0 and a temperature of 19°C, retting of sulphur dioxide treated moist flax (flax to water ratio of 1:10) was achieved with Flaxzyme concentrations as low as 0.5 ml litre”‘,much lower than the previously reported minimum of 3.0 ml litre’.     

Bacterial Population Structure of the Jute-Retting Environment

Jute is one of the most versatile bast fibers obtained through the process of retting, which is a result of decomposition of stalks by the indigenous microflora. However, bacterial communities associated with the retting of jute are not well characterized. To investigate the presence of microorganisms during the process of jute retting, full-cycle rRNA approach was followed, and two 16S rRNA gene libraries, from jute-retting locations of Krishnanagar and Barrackpore, were constructed. Phylotypes affiliating to seven bacterial divisions were identified in both libraries. The bulk of clones came from Proteobacteria ( approximately 37, 41%) and a comparatively smaller proportion of clones from the divisions-Firmicutes ( approximately 11, 12%), Cytophaga-Flexibacter-Bacteroidetes group (CFB; approximately 9, 7%), Verrucomicrobia ( approximately 6, 5%), Acidobacteria ( approximately 4, 5%), Chlorobiales ( approximately 5, 5%), and Actinobacteria ( approximately 4, 2%) were identified. Percent coverage value and diversity estimations of phylotype richness, Shannon-Weiner index, and evenness confirmed the diverse nature of both the libraries. Evaluation of the retting waters by whole cell rRNA-targeted flourescent in situ hybridization, as detected by domain- and group-specific probes, we observed a considerable dominance of the beta-Proteobacteria (25.9%) along with the CFB group (24.4%). In addition, 32 bacterial species were isolated on culture media from the two retting environments and identified by 16S rDNA analysis, confirming the presence of phyla, Proteobacteria ( approximately 47%), Firmicutes ( approximately 22%), CFB group ( approximately 19%), and Actinobacteria ( approximately 13%) in the retting niche. Thus, our study presents the first quantification of the dominant and diverse bacterial phylotypes in the retting ponds, which will further help in improving the retting efficiency, and hence the fiber quality.     

Bacteria Responsible for the Retting of Brazilian Flax

Twenty-two species of bacteria were isolated from Linum usitatissimum stored for retting. Achromobacter parvulus, Clostridium beijerinckii, C. saprogenes, C. saccharoacetoperbutylicum, C. perenne, and Pseudomonas aeruginosa and its achromogenic variety are retting agents. The last species mentioned performs the retting in only 72 hr. This is the first time A. parvulus has been shown to be a retting agent.     

Studies on the microbiology of cassava retting for foo-foo production

O kafor N. I jioma B. O yolu , C. 1984. Studies on the microbiology of cassava retting for foo-foo production. Journal of Applied Bacteriology 56 , 1–13.
Five bacteria ( Bacillus, Lactobacillus, Klebsiella, Leuconostoc, and Corynebacterium ) and a yeast ( Candida spp.) were isolated from cassava being fermented for foo-foo production. Retting of cassava was assessed by determining the weight required to crush cylindrical cassava pieces. A weight in excess of 2.5 kg was required to crush an unfermented peeled cassava cylinder 4 mm diameter and 4 cm long whereas a weight as small as 20 g could crush the same piece after retting. The organisms were studied for their ability to cause retting of sterile cassava pieces, alone or in various combinations. Retting did not occur unless either the Bacillus sp. or the Corynebacterium sp. was present. Only these two organisms hydrolysed starch. The lactic acid bacteria lowered the pH of the fermenting medium although they did not bring about retting. The typical aroma of foo-foo was produced, however, only when the lactic acid bacteria were present in the mixture. Only the Corynebacterium sp., was, however, shown to produce pectinolytic enzymes and it is possible that the Bacillus sp. caused retting by disintegrating other cell components. The typical aroma of foo-foo is disliked by some individuals and it seems possible that foo-foo with a bland aroma, which will presumably be more acceptable to this group, can be produced by using organisms causing retting while excluding those forming lactic acid.     

亚麻微生物脱胶菌种的筛选与鉴定

在研究天然水沤法脱胶的过程中,通过初筛、复筛,从沤麻主生物期的沤麻液中筛选出两株茵落周围产生透明圈较大、脱胶酶活较高的菌株。通过形态观察,并对其多项生理、生化指标进行了分析研究,初步鉴定并命名为枯草芽孢杆菌A1和B1。初步加茵脱胶实验表明：枯草芽孢杆菌A1产生果胶酶、木聚糖酶,而不产生纤维素酶,脱胶周期为72小时;枯草芽孢杆茵B1产生果胶酶、木聚糖酶和纤维素酶,脱胶周期为50小时。     

Changes in the bacterial community structure and diversity during bamboo retting

Microbial retting is a critical step in obtaining fiber bundles from bamboo culm using indigenous microorganisms. A cultivation-independent technique for monitoring the changes in bacteria community during bamboo retting was applied in this work. This technique involves genetic profiling of PCR-amplified small-subunit rRNA and the single-strand conformation polymorphism (SSCP) gel analysis of the PCR-amplified 16S rDNA fragments. The study revealed that both the structure and the diversity of investigated communities varied with the incubation periods and sample locations. The bacteria bands from SCCP gel profiles related to Bacillus sp. decreased in intensity, and Phaeospirillum sp. and Azospirillum brasilense completely disappeared during the 4(th) and 5(th) month of incubation, while the bands related to the Sphingomonas japonica, Alphaproteobacterium Ellin335 and Microbacterium sp. increased. The bands closely related to Sphingomonads, Brevundimonas brasilense, Pseudoclavibacter sp., Agrococcus jenensis and Oxalophagus oxalicus remained dominant during the whole incubation period. This study showed that the use of PCR assay targeting 16S rRNA and SCCP profiling provided valuable information on monitoring the bacteria dynamic changes occurring in the bacteria community during bamboo retting, which is crucial for controlling the quality of the retting process and improving the retting efficiency, and thus benefits for fiber recovery.     

Polygalacturonase is the key component in enzymatic retting of flax

Seven commercial enzyme mixtures were tested for their ability to perform retting of flax (i.e. to separate flax fibers by partly removal of middle lamella) and were assayed for hydrolysis of xylan, cellulose and four kinds of pectin. The only activity that showed correlation to the ability to perform retting was the degradation of low esterfied pectin. A purified Aspergillus niger polygalacturonase was also shown to be able to perform retting. From this data it is hypothesized that degradation of the smooth regions (i.e. non-methylated polygalacturonase) in the middle lamella pectin is the most important step in enzymatic retting.     

The active component in the flax-retting system of the zygomycete Rhizopus oryzae sb is a family 28 polygalacturonase

The zygomycete Rhizopus oryzae sb is a very efficient organism for retting of flax, the initial microbiological step in the process of making linen. An extracellular polygalacturonase, when isolated could perform retting, and therefore probably is the key component in the retting system of R. oryzae. This was purified and characterized. The purified enzyme has a molecular mass of 37,436 Da from mass spectrometric determination, an isoelectric point of 8.4, and has non-methylated polygalacturonic acid as its preferred substrate. Peptide sequences indicate that the enzyme belongs to family 28, in similarity with other polygalacturonases (EC. 3.2.1.15). It contains, however an N-terminal sequence absent in other fungal pectinases, but present in an enzyme from the phytopathogenic bacterium Ralstonia solanacearum. The biochemical background for the superior retting efficiency of R. oryzae sb is discussed.     

Drastic changes in lake ecosystem development as a consequence of flax retting: a multiproxy palaeolimnological study of Lake Kooraste Linajärv,Estonia

This study demonstrates the power of multiproxy palaeolimnological analyses in investigating environmental changes in the Lake Kooraste Linajärv ecosystem through historical time in response to flax retting. Flax retting history was proven by applying pollen and macrofossil evidence and by using several biotic and geochemical proxies on a sediment core. Continuous findings of flax pollen and macrofossil remains in lake sediments were considered as strong evidence for the occurrence of retting. Analyses of the well-dated sediment core show the consequences of flax retting in the lake. As a result, the once clear soft water oligotrophic endorheic lake with limited sedimentation has turned into a hypertrophic high-sedimentation lake with anoxic bottom water, strong stratification and intense water blooms. Despite the fact that flax retting was forbidden in Estonia around ad 1950s and retting has not occurred over the last six decades, anthropogenic alterations were so pervasive in the past, that they have prevented any lake water improvements until the present-day.     

The influence of the pH on the pectinolytic activity of flax-retting bacteria

The pectinase produced during the anaerobic retting of flax appeared to have a pH optimum between 5.4 and 5.6. Continuous neutralization during the fermentation, however, induced the production of a pectinase with a pH optimum of 7.1.The majority of the pectin splitting bacteria in the acid and in the neutral retting liquors belonged to the speciesClostridium pectinovorum.Pure culture studies withCl. pectinovorum at fixed pH levels showed that the pectinase produced is adapted to the pH of the environment. No differences in pH dependency could be established between the hemicellulases from the acid and the neutral retting liquor.Although a pH of 6.5 is far from optimal for the hemicellulase, the actual hemicellulolytic activity in the neutral pH retting method is greater than the activity of the normal, acid retting liquor. This fact supports the theory that hemicellulase is responsible for losses in fibre quality and quantity in the neutral pH retting method.     

Retting pits for textile fibre plants at Danish prehistoric sites dated between 800 b.c. and a.d. 1050

During the last decade, a new type of structure has been found at several archaeological sites in Denmark. These structures can be interpreted as having been used for retting the stems of textile plants such as Linum usitatissimum L. (flax), Cannabis sativa L. (hemp) and Urtica dioica L. (nettle). In order to obtain fine threads for textile production, these plants need to pass through several biological and technical processes. The first process is the retting of the plant stems to dissolve the pectin which fixes the fibres to the stalk. This can either be done by water retting, where the plant stems are soaked in lakes, rivers or waterlogged pits, or by field retting, where the stems are laid out in a field in order to absorb dew. The first method is shorter in time and the process is easier to control. In this article, details of archaeological structures are presented from eight sites in southern Scandinavia that can be interpreted as textile plant retting pits. The constructions of the pits are described, as well as the archaeological contexts and the relevant associated archaeobotanical records. Some of the presented sites, of which the oldest are dated to the late Bronze Age and early pre-Roman Iron Age (800–250 b.c.) and the youngest to the Viking Age (a.d. 750–1050), indicate a large-scale production of flax that had been underestimated up to now.     

Further observations on the bacteriology of jute retting

Bacteria capable of retting jute are present in pond water, in the soil of jute fields, and on the surface of jute plants. They probably enter stems over the whole surface through stomata, as well as through cut ends and leaf scars, after immersion for retting. Under laboratory conditions the shortest period of retting, three days, was achieved withBacillus polymyxa at a temperature of 40°. Retting in a tank was appreciably hastened by using the same water for successive batches of jute. Prolonged immersion involves the risk of over-retting, probably because of the action of cellulolytic bacteria. For natural retting, still the most appropriate process in East Pakistan, large clean ponds are thought to provide the most suitable 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%.     

Investigation of the bacterial retting community of kenaf (Hibiscus cannabinus) under different conditions using next-generation semiconductor sequencing

The microbial communities associated with kenaf (Hibiscus cannabinus) plant fibers during retting were determined in an effort to identify possible means of accelerating this process for industrial scale-up. Microbial communities were identified by semiconductor sequencing of 16S rRNA gene amplicons from DNA harvested from plant-surface associated samples and analyzed using an Ion Torrent PGM. The communities were sampled after 96 h from each of three different conditions, including amendments with pond water, sterilized pond water, or with a mixture of pectinolytic bacterial isolates. Additionally, plants from two different sources and having different pretreatment conditions were compared. We report that the best retting communities are dominated by members of the order Clostridiales. These bacteria appear to be naturally associated with the plant material, although slight variations between source materials were found. Additionally, heavy inoculations of pectinolytic bacteria established themselves and in addition their presence facilitated the rapid dominance of the original plant-associated Clostridiales. These data suggest that members of the order Clostridiales dominate the community and are most closely associated with efficient and effective retting. The results further suggest that establishment of the community structure is first driven by the switch to anaerobic conditions, and subsequently by possible competition for nitrogen. These findings reveal important bacterial groups involved in fiber retting, and suggest mechanisms for the manipulation of the community and retting efficiency by modifying nutrient availability.     

Relationship of pectic enzyme of macrophomina phaseoli with stem-rot disease and retting of jute

Summary Culture filtrates of three strains ofM. phaseoli were found to have pectic enzymes which macerated potato discs and separated the fibre strands of jute stem, but were not toxic. The filtrates with this principle also caused, under controlled conditions, defoliation and wilting of jute plants which are the symptoms of the stem-rot disease.The pectic enzyme contained in the strain MP-C was found to be more virulent in causing the disease and more effective in retting Jute. Thus a relationship of pectic enzyme ofM. phaseoli with stemrot disease and retting of jute has been indicated.Microbiologist, Assistant Biochemist, Research Assistant and Director, respectively.     

Changes in microbial populations during anaerobic flax retting

D onaghy , J.A., L evett , P.N. & H aylock , R.W. 1990. Changes in microbial populations during anaerobic flax retting. Journal of Applied Bacteriology 69 , 634–641.
The bacterial flora of industrial and laboratory scale anaerobic flax rets were determined at intervals throughout the rets. Although after an initial lag period total bacterial numbers remained roughly constant there were fluctuations in the bacterial species constituting the total. Pure culture rets and enzyme assays were used to determine which strains had retting potential. Of the strains demonstrated to have retting ability Bacillus licheniformis and B. subtilis were numerically dominant from 10 to 40 h and were succeeded in dominance by Clostridium acetobutylicum and Cl. felsineum .