A METHOD OF TREATING A SUNFLOWER PLANT STEMS

Abstract

A method of treating a sunflower plant stem is disclosed. The method comprises the steps of: selecting a sunflower plant, removing the flower head and leaves from the stem and preparing the stem for enzymatic treatment by slitting the stem lengthways, removing the inner core from the stem; a) treating the cut stem with a pectinase containing a first buffer solution, for 24 hours with shaking at a pH of 3.8-8.5, and at a temperature of from 20-60 C.; b) removing the stem and washing with water, c) placing the stems into a second buffer solution containing xylanase, at a pH of from 7.0-8.0 and at a temperature of from 37-50 C. for 24 hours with shaking; d) removing the stems and washing with water e) placing the stems into a third buffer solution containing feruloyl esterase, at a pH of 7.2-8.0 containing 0.01-0.05% feruloyl esterase, at a temperature of from 37-50 C. for up to 24 hours, f) removing the stems and washing with water, g) pressing the stems to remove unwanted plant matter.

Claims

1. A method of treating a sunflower plant stem, the method comprising the steps of: a) selecting a sunflower plant, removing the flower head and leaves from the stem and preparing the stem for enzymatic treatment by slitting the stem lengthways, removing the inner core from the stem; b) treating the cut stem with a pectinase containing a first buffer solution, for 24 hours with shaking at a pH of 3.8-8.5, and at a temperature of from 20-60 C.; c) removing the stem and washing with water, d) placing the stems into a second buffer solution containing xylanase, at a pH of from 7.0-8.0 and at a temperature of from 37-50 C. for 24 hours with shaking; e) removing the stems and washing with water f) placing the stems into a third buffer solution containing feruloyl esterase, at a pH of 7.2-8.0 containing 0.01-0.05% feruloyl esterase, at a temperature of from 37-50 C. for up to 24 hours, g) removing the stems and washing with water, h) pressing the stems to remove unwanted plant matter.

2. A method according to claim 1, wherein one or more of the following is selected to break open the stem: mechanical rollers, hydrothermal or enzymatic.

3. A method according to claim 1, wherein the first buffer solution is a tris-buffer solution containing 0.01-0.20% pectinase.

4. A method according to claim 3, wherein the pectinase is from Aspergillus niger.

5. A method according to claim 1, wherein the first buffer solution is at a pH of 7.2.

6. A method according to claim 1, wherein the temperature is maintained during step b) at a temperature of 26 C.

7. A method according claim 1, wherein the second buffer solution is a Tris-buffer solution containing a xylanase.

8. A method according to claim 7, wherein the pH of the second buffer solution is 8.0.

9. A method according to claim 1, wherein the temperature is maintained during step d) at 37 C.

10. A method according to claim 1, wherein the third buffer solution is a Tris-buffer solution containing a feruloyl esterase.

11. A method according to claim 10, wherein the feruloyl esterase is from Anaeromyces mucronatus.

12. A method according to claim 10, wherein the stems are maintained in the third buffer solution for up to 48 hours.

13. A method according to claim 1, wherein step h) is carried out using a roller.

14. A method according to claim 1, wherein the pressed stems are treated with a basic solution for 12 hours at 30 C.

15. A method according to claim 1, wherein the washing in step g) is carried out with boiling water.

16. A method of treating a fibre yarn with a wax obtained from a sunflower seed to waterproof a yarn, the method comprising the steps of: a) pre-treating the fabric with a water wash and drying the fabric; b) contacting the fabric with a solution of a cationic starch at a concentration of 2-10 g/l, c) applying a layer of a sunflower wax suspension in water to the fabric, by soaking or by spraying, the particles of wax having a particle size of from 100-160 m; d) repeating the application of a starch layer and wax layer alternately, preferably to give four layers of each of the starch and the wax; e) curing the fabric.

17. A method according to claim 16, wherein the concentration of the starch is 5 g/l.

18. A method according to claim 16 or claim 17, wherein the a fabric rinse step with water is included after the first application of cationic starch solution.

19. A method according to claims 16-18, wherein the curing step is carried out at a temperature of from 72-85 C.

20. A method according to claims 16-19, wherein the curing step is carried out for 20-45 minutes.

21. A method according to claims 16-20, wherein the fabric is contacted by soaking with the cationic starch solution.

22. A method according to claim 21, wherein the fabric is rinsed with water following the soaking step.

23. A method according to claims16-20, wherein the fabric is contacted by spraying with the cationic starch solution.

24. A method according to claims 16-23, wherein the fabric is contacted by soaking with the wax suspension.

25. A method according to claims 24, wherein the fabric is rinsed with water following the soaking step.

26. A method according to claims16-23, wherein the fabric is contacted by spraying with the wax suspension.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0028] The drive to utilise a renewable source for fabric materials is increasing as manufacturers seek to reduce the carbon footprint of clothing and other materials and to reduce reliance on fossil fuels for the raw materials, due to the increasing costs thereof and also the finite nature of such fossil fuel resources. There is also an increased push to diversify the plant fibres that are used for clothing and textiles and to decrease our reliance on cotton, which has resource-intensive cultivation.

[0029] Cottonized hemp is being championed as a cotton alternative. However, hemp has to undergo an additional degumming process after the fibres have been obtained to achieve a cotton-like fibre. This can be lengthy and can also heavily rely on a chemical-intensive process, reducing its commercial viability to compete with cotton.

[0030] One such renewable source which has hitherto not been considered is the sunflower plant. Although the obtention of an oil from sunflower seeds is well known, the use of other parts of the sunflower, such as the stem, is less well advanced.

[0031] The present invention in one aspect relates to a multi-stage process for the provision of a fibre which can be used in the textile industry to produce a woven, knitted, non-woven textiles, or alternative down material, which is more like cotton than the equivalent retted hemp fibres, without the additional degumming process. In the disclosed process, the stems of a sunflower are treated to remove the materials surrounding the fibres in the stem, leaving the fibres available to be formed into the fabric.

[0032] In broad terms, the process used is an enzyme retting process, following a pre-treatment series of steps. The pre-treatment steps involve breaking down xylan, pectin, and hemicelluloses in the plant stem. The breakdown products can then be more easily removed from association with the fibre materials to enable intact fibres to be isolated and processed for post treatment.

[0033] In more detail, in an exemplary process, the following stages and stage-steps are undertaken. In the first stage, a xylanase enzyme is obtained for use in the subsequent treatment of the plant stem. In the second stage, the stems are prepared and the pectin removed to loosen the links between cells in the plant-stem cell walls, and thus allow the cellular material to be more easily disrupted. This is followed by removal of cinnamoyl residues from the plant cell wall to further aid the degradation of the plant cell walls. Finally, the degraded plant cell walls can be further removed in a mechanical or chemical washing procedure to leave the required plant fibres for purification and drying.

[0034] In more detail, the first stage of isolating a suitable hemicellulase, xylanase, is described. The purified xylanase can be commercially purchased or obtained through recombinant expression in a microbial system. The steps undertaken to purify xylanase from a recombinant expression system in E. coli are described below. This method provides a cheaper and more sustainable alternative to purchasing pre purified enzymes commercially and can be scaled up as desired. A version of this process can also be applied to other enzymes used in this text.

Step (i)

[0035] Steps (i)-(iii) are for protein expression & scaling and can be applied to obtain all enzymes outlined with appropriate modifications. Commercially available enzymes can also be used which skip out steps (i)-(iii).

[0036] A vector expressing xylanase under a Isopropyl -D-1-thiogalactopyranoside (IPTG) inducible promoter is inserted in Escherichia coli strain BL21 competent cells by chemical transformation. Other methods are equally suitable. The BL21 containing the xylanase vector is selected by growing the cells in Luria Broth Agar plates containing selective antibiotic and grown at 37 C. overnight.

Step (ii)

[0037] In this step, 5 single colonies are selected and transferred to 10 ml Luria Broth liquid media containing the appropriate selective antibiotics. The mixture obtained is then incubated overnight at 37 C. with shaking at 180 rpm.

Step (iii)

[0038] In this step, the bacterial culture grown in Step (ii) are scaled-up in size. The 10 ml overnight cultures are inoculated in a total volume of 1 L Luria Broth culture containing suitable antibiotics and placed in 2 L Erlenmeyer flasks for optimal aeration. These are then incubated at 37 C., with shaking at 200 rpm until the optical density (OD.sub.600nm) reaches 0.6. IPTG is then added to a final concentration of 0.2 mM to each flask, which is then incubated overnight at 18 C. with 200 rpm shaking.

[0039] The cells produced are then harvested, by firstly centrifuging the incubated suspension at 5000 rpm for 10 minutes. The cell pellets obtained are then suspended in an aqueous Tris-buffer solution (15 ml), having a pH of 8 and containing tris(hydroxymethyl)aminomethane (Tris) (at 2.42 g/L) sodium chloride (17.53 g/L). At this stage the suspension can be frozen at 20 C. for later use if so desired. The suspension is sonicated for 5 minutes, while kept in an ice bath, using 30 s pulses, and then centrifuged at 6000 rpm for 5 minutes. The xylanase enzyme aqueous mixture is collected from the supernatant and kept for further use.

Step (iv)

[0040] The xylanase generated in the above steps is then utilised in the retting process as now described. The stems from sunflowers are prepared by the removal of the head and the leaves from the stem. The prepared stems are prepared by crushing or cutting lengthways, and, optionally, its inner core removed. Other methods known in the art, including mechanical, hydrothermal or enzymatic can also be used, followed by the inner core preferably being removed. The cut stems are then added to a vessel containing a buffer solution preferably; Tris-buffer solution at a pH of from 3.8-8.5 , and preferably 7.2. Pectinase, such as the commercially available ones obtained from Aspergillus niger, is added to the buffer solution at a concentration of 0.01-0.20 v/v. At this stage it is advisable that the stems are at least 50% to 100% submerged in the buffer mixture. Optionally, a buffer solution can be sprayed onto the stems to reduce reagent consumption. The container holding the buffer solution and the stems is closed and incubated at a temperature of from 20-60 C. and preferably 26 C. for between 18 and 48 hours, preferably 24 hrs with shaking. The stems are then removed from the buffer solution and washed with boiling water.

[0041] The treated stems are then added to a buffer solution preferably Tris-buffer solution at a pH of from 6.0-9.0 and preferably 8.0 and at a temperature of from 37-50 C. and preferably 37 C., and it is advisable that the stems are at least 50% to 100% submerged. Optionally, a buffer solution can be sprayed onto the stems to reduce reagent consumption. The buffer solution contains the xylanase from step (iii) or equivalent commercially available enzyme above at a concentration of from 0.01-1.00% v/v, although the concentration chosen depends on the activity of the xylanase obtained. The container holding the buffer solution and the stems is closed and incubated at a temperature of 25-60 C. and preferably 37 C. for between 18 and 48 hours, preferably 24 hrs with shaking. The stems are then removed from the buffer solution and washed with boiling water.

[0042] The stems from the previous stage are then added to a buffer solution preferably Tris-buffer solution, at a pH of from 5.0-8.5, preferably from 7.2-8.0, and it is advisable such that the stems are at least 50% to 100% submerged. Optionally, a buffer solution can be sprayed onto the stems to reduce reagent consumption. Feruloyl esterase as a solid or in solution, optionally from Anaeromyces mucronatus, is added to a concentration of 0.01-0.05 % v/v. The container holding the buffer solution and the stems is closed and incubated at 37-50 C. for 24 hours with shaking. If preferred, the incubation can be carried out for up to a 48 hour period. The stems are then removed from the buffer solution and washed with boiling water. The washed stems are then pressed with a roller to flatten them out and separate the fibres. Any other known method including mechanical, hydrothermal or enzymatic treatment can be used for stem post processing.

Step (v)

[0043] The next stage of the process to soften the fibres is optional depending on end use of the fibre. The treated stems from the previous stage are then soaked in a hydroxide solution, preferably; sodium hydroxide solution (1.6% w/v), overnight at 26-30 C., preferably 30 C. to further soften the fibres or washed with industrial soap. If the separation is acceptable, the stems are washed with boiling water or autoclaved at 120-130 C., preferably 125 C. for 15 minutes to remove excess degraded plant material. Other steam-based methods known in the art can be used. The stems are further washed to remove degraded plant material and processed suitably for desired end use.

Step (vi)

[0044] The fibres thus obtained can be used as a down alternative, for non-woven fabrics or are suitable for being spun together to form a yarn which is suitable for knitting or weaving. The fibres can optionally also be blended with other natural fibres such as flax, hemp or cotton, if desired.

[0045] With regard to a second aspect of the invention relating to a method for rendering a fibre yarn such as that obtained above to be waterproof, then the following exemplifies such a method in accordance with the current invention.

[0046] To boiling water, a cationic starch is added to give a final concentration of 2-10 g/L, preferably 5 g/L, with agitation, such as stirring for 15 minutes. Separately, sunflower wax is added to boiling water at a concentration of 10 g/L and with sonication to obtain a homogeneous solution. <Does this form a solution or a distribution of liquid wax in water?> The sonicated mixture is cooled quickly in an ice bath and the suspension is passed through a sieve with pores ranging from 100-160 m with the flow-through being collected and retained for the further stages.

[0047] The fabric to be treated is pre-washed with water and fully dried. As examples of fabrics treated, then 100% cotton poplin and 100% hemp can be cited. The coating is applied using an alternate layer of the starch solution and the wax solution prepared as above. The fabric is coated with the starch solution by either fully soaking in the solution or spraying therewith. The fabric is then rinsed in water, particularly if soaking has been used to deposit the layer. Where spraying has been used to apply the layer, then the rinse stage can be omitted. The starch-coated fabric is then soaked or sprayed with the wax suspension. A rinse step is then carried out, especially where soaking has been used. These steps are then repeated 7-10 times to give 4 or more coats of each of the starch and the wax. The fabric is then left to dry overnight. Finally, the fabric is cured in an oven at 72-85 C. for 20-45 minutes. Utilising the above process, a fabric can be produced which holds a water droplet for over 90 minutes. After the waterproof ability is reduced, the treatment can be repeated as many times as needed.