Regular articleConstruction of a pilot plant for producing fine linen fibers for textiles
Graphical abstract
Highlights
► A pilot plant for producing fine flax fibers with a new bioprocess was constructed. ► The plant was operated for one year and 140 kg of fine fibers were produced. ► The process is reliable, easy to scale-up and the equipment needed is simple. ► All process liquors could be reused several times producing high quality fibers. ► The new process avoids weather-related risks of traditional fiber production methods.
Introduction
Flax, Linum usitatissimum is an annual herb cultivated since antiquity for its useful textile fibers (linen). The fibrous cells, localized in the periphery of the stem, form bundles of overlapping fibers from 30 to 90 cm in length. The fibers are glued together by pectic material and account for only 30% of the flax plant. As the pectic material is degraded, the fibers divide during retting, carding and spinning. Short, broken fibers (tow) are used to make coarse fabrics and cordage, while long fibers, the most valuable part of the plant, are used for strong threads and fine linen [1].
The traditional methods used to extract the fibers from the stem are dew and water retting. In both procedures microorganisms (bacteria and fungi) break down the woody tissues and dissolve the pectic substances binding the fibers. In water retting the stems are submerged in water for some days. This method produces the highest quality fibers, but the waste liquors are highly polluting. In dew retting the fibers are spread out on the field and exposed to dew and sun for several weeks. Nowadays dew retting is common practice in the flax industry in Western Europe [1], [2], [3]. Dew retting is highly weather dependent. A wet weather produces weak and degraded fibers or even the loss of the entire crop. A dry weather produces under-retted coarse fibers with contaminating shives. In both cases the quality of the fibers is negatively influenced [4]. After dew or water retting the stems are dried and scutched to separate the fibers from the rest of the stem. The remaining nonfibrous matter is removed by hackling [1].
Recently we described a laboratory-scale process for refining the flax fibers using the pectinolytic strain Geobacillus thermoglucosidasius PB94A (DSM 21625). This strain degraded selectively hemp and flax pectin at high temperatures in alkaline environments (60 °C and pH 8.5) [5]. An advantage of using a process with a thermophilic strain, is that the temperature of 60 °C, serves as a barrier against mesophilic cellulolytic contaminating microorganisms that damage the flax fibers.
In contrast to some commercial pectinases, the enzymes excreted by G. thermoglucosidasius PB94A were free of cellulolytic side-activity that could damage the cellulose of the flax fibers. Moreover, using a whole cell system instead of the crude enzyme supernatant or a commercial pectinase preparation allows to use the treatment liquor more than once. This is positive for the environment and helps to decrease the costs.
Pilot or industrial scale facilities to test if this new process is a technically feasible alternative to dew and water retting do not exist but were needed. Existing processes for treating flax use the whole plant [6], this is not suitable for our new process that uses green decorticated fibers, because the fibers would bend and tangle. Using decorticated fibers for the new process has the advantage that they are only 30% of the weight of the flax plant, this allows to save resources. Therefore, a pilot plant for the testing the new process on a technical scale was designed and built.
Section snippets
Materials and methods
Chemicals were purchased from Merck (Darmstad, Germany), Fluka (Neu-Ulm, Germany), Sigma–Aldrich (Munich, Germany), Roth (Karlsruhe, Germany). Adulcinol BUN was a gift from Zschimmer & Schwarz Mohsdorf GmbH & Co KG (Burgstädt, Germany).
The flax plants used for this work were grown in 2004 in Mielsdorf, Germany. The plants were decorticated green and the fibers were baled and stored for using in the experiments.
The water used for the analysis and the media preparation was HPLC-grade. For the
Pilot plant concept
A laboratory-scale process for the production of high quality fibers was developed, wherein the fibers were cooked in a mild alkaline bath with Na2CO3 at 90–100 °C, followed by an incubation with the thermoalkaliphilic and pectinolytic strain G. thermoglucosidasius PB94A at 50–60 °C and pH 8–9, followed by a shive-removal wash with H2O2 at 50 °C, and finally by a wash with a softener solution at 50 °C and pH 4–5 [5]. In these experiments carried out in beakers the fibers were allowed to float
Conclusions
A 200-L-scale pilot-plant for producing fine linen fibers was designed, built and operated for one year. In the pilot-plant a process using whole cells of the thermoalkaliphilic pectinolytic strain G. thermoglucosidasius PB94A and raw decorticated fibers was established. In experiments reusing the bacterial culture six times, all treated fibers reached the desired quality. The new process is a reliable option for the production of valuable fine long linen fibers on a technical scale and leads
Acknowledgements
This study was supported by the Fachagentur Nachwachsende Rohstoffe with the project 22006303.
The pilot plant was built with the help of Bernhard Pallaks, Gerhard Schietke, and Cord Heineking of the TUHH.
We thank the students Ricardo Martínez Banda and Ranganathan Budhi Venkatesan for their collaboration in the experiments at the pilot plant.
We want to thank the company HiTec Zang GmbH (Herzogenrath, Germany) for providing the RI-CAD software for the technical diagrams.
We thank the company
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