MODIFICATION ENZYMATIQUE DE LA LIGNINE POUR SA SOLUBILISATION ET APPLICATIONS

Abstract

Disclosed is a lignin that is soluble in a medium having a pH greater than or equal to 4, a solution containing same, a method for producing same, and uses thereof, in particular for preparing lignin fibers and carbon fibers. Soluble lignin may be obtained by enzymatic modification.

Claims

1. A lignin soluble in water at a pH greater than or equal to 4 and less than 12 wherein said soluble lignin is obtained by the enzymatic route.

2. The soluble lignin according to claim 1, wherein said lignin is infusible.

3. A process for the solubilization of lignin wherein said process comprises bringing a lignin into contact with at least one bilirubin oxidase enzyme (BOD), in the presence or absence of a redox mediator, and obtaining a water-soluble lignin with a pH greater than or equal to 4.

4. The soluble lignin according to claim 1, wherein said lignin is a lyophilizate.

5. A solution with a pH greater than or equal to 4 comprising a lignin soluble in water at a pH greater than or equal to 4 and less than 12, wherein said soluble lignin is obtained by the enzymatic routes.

6. The solution according to claim 5, wherein said solution comprises at least 5% by mass of soluble lignin relative to the weight of the total mass of the solution.

7. The solution according to claim 5, wherein the solvent of the solution comprises or consists of water.

8. The solution according to claim 5 wherein said solution comprises a water-soluble polymer, and, for example, a water-soluble polysaccharide, and more particularly alginate.

9. Fibers comprising a lignin soluble in water at a pH greater than or equal to 4 and less than 12, wherein said soluble lignin is obtained by the enzymatic route, and at least one polymer that is soluble in water.

10. The fibers according to claim 9, wherein said fibers comprise an alginate.

11. The fibers according to claim 9, wherein said fibers comprise a mass concentration of lignin greater than or equal to 60% in the lignin fiber.

12. A process for the production of lignin fibers, wherein said process comprises: preparing lignin soluble in water at a pH greater than or equal to 4 and less than 12, wherein said soluble lignin is obtained by the enzymatic route, bringing the soluble lignin into contact with an aqueous solution, optionally in the presence of a water-soluble polymer, coagulation or crosslinking of lignin, optionally in the presence of the water-soluble polymer, with a coagulating or crosslinking agent, and obtaining lignin fibers.

13. The process for manufacturing carbon fibers, wherein said process comprises the calcination of lignin fibers as defined in claim 11.

14. A process for manufacturing carbon fibers by aqueous process, wherein said process comprises: preparing lignin soluble in water at a pH greater than or equal to 4 and less than 12, wherein said soluble lignin is obtained by the enzymatic route, bringing the soluble lignin into contact with an aqueous solution, optionally in the presence of a water-soluble polymer, coagulation or crosslinking of lignin with a coagulating or crosslinking agent, obtaining lignin fibers, possibly washing with water and then drying the lignin fibers, calcining said lignin fibers, and obtaining carbon fibers.

15. The lignin according to claim 1, wherein said lignin is soluble in water at a pH greater than or equal to 7.

16. The lignin according to claim 1, wherein said lignin is soluble in water at a pH less than 10.

17. The process according to claim 3, wherein said lignin is soluble in water at a pH, greater than or equal to 7.

18. The process according to claim 3, wherein said lignin is soluble in water at a pH less than 10.

19. The fibers according to claim 9, wherein said lignin is soluble in water at a greater than or equal to 7.

20. The fibers according to claim 9, wherein said lignin is soluble in water at a pH less than 10.

21. The process for the production of lignin fibers according to claim 12, wherein said lignin is soluble in water at a greater than or equal to 7.

22. The process for the production of lignin fibers according to claim 12, wherein said lignin is soluble in water at a pH less than 10.

23. The process for manufacturing carbon fibers by aqueous process according to claim 14, wherein said lignin is soluble in water at a greater than or equal to 7.

24. The process for manufacturing carbon fibers by aqueous process according to claim 14, wherein said lignin is soluble in water at a pH less than 10.

Description

EXAMPLES

Example 1aSolubilization of Lignin with a Purified Enzyme

[0097] 2 g of kraft lignin, purchased from Sigma-Aldrich under the reference (370959) are taken up in 100 ml of 50 mM Borate pH9 buffer and sonicated for 30 min under the following conditions: amplitude 20%, 0.5 s ON, 0.5 s OFF (Branson).

[0098] 5.4 mg of BOD of Bacillus pumilus are then added to this solution at 37 C. with stirring with a magnetic bar at 100 rpm and a bubbling of compressed air at 0.1 l/min.sup.1, for 16 hours. The solution is then sonicated for 30 min under the conditions described above, and then dialyzed in a 100 ml 10 kDa dialysis rod, in three 4 l baths of mQ water, the first of 2 hours, the second of 4 hours, and the third for the night. The solution is centrifuged for 5 minutes at 1500 rpm. The supernatant containing soluble lignin is lyophilized overnight and stored at room temperature.

Example 1bSolubilization of Lignin with an Unpurified Enzyme

[0099] 2 g of kraft lignin, purchased from Sigma-Aldrich under the reference (370959) are taken up in 100 ml of 50 mM Borate pH9 buffer and sonicated for 30 min under the following conditions: amplitude 20%, 0.5 s ON, 0.5 s OFF (Branson).

[0100] 20 g of E. coli Origami B DE3 pellet containing the BOD of Bacillus pumilus, obtained as described in Gounelle et al. (J. Biotechnol, 19-25 2016), is resuspended in 120 ml of Borate pH9. The bacteria are comminuted by 3 passages in a cell mill (Constant Systems Ltd, CellD) at 2200 bar. The solution is centrifuged at 21,000 g for 1 hour and the supernatant is filtered at 0.22 m and stored in a 20 ml aliquot at 80 C.

[0101] 20 ml of supernatant containing the BOD of Bacillus pumilus, previously prepared, are added to the lignin solution at 37 C. with stirring with a magnetic bar at 100 rpm and bubbling with compressed air at 0.1 l/min.sup.1 for 16 hours. The solution is then sonicated for 30 min under the conditions described above, and then dialyzed in a 100 ml 10 kDa dialysis unit, in three 4 l baths of mQ water, the first of 2 hours, the second of 4 hours, and the third for the night. The solution is centrifuged for 5 minutes at 1500 rpm. The supernatant containing soluble lignin is lyophilized overnight and stored at room temperature.

Example 2Manufacture of Composite Lignin Fibers

[0102] The lyophilized lignin obtained in Example 1 is resolubilized in water. Sodium alginate (Protanal LF200 FTS, FMC Corporation) is added to obtain a homogeneous, aqueous solution containing 5.67% by mass of lignin and 0.66% by mass of alginate. This solution is then injected, at a speed of 12 ml/h into a coagulation bath containing a solution of 100 mM of calcium chloride, using a syringe pump and a 300 m nozzle. The coagulated fiber is then removed continuously at a speed of 1.3 m/min, then continuously rinsed in a tank for washing with distilled water at a speed of 1.7 m/min. The washed composite lignin fiber is then dried at 60 C. in an infrared oven at 1.7 m/min and then directly formed into a coil at a speed of 1.8 m/min. At the end of the manufacturing process, a homogeneous lignin fiber is obtained at a mass concentration of 90.9% lignin.

Example 3Preparation of Carbon Fibers

[0103] Lignin fibers obtained according to Example 2 are used in this example.

[0104] A carbon fiber is obtained after calcination under an inert atmosphere of this fiber at 1000 C. (temperature rise of 5 C./min and a plateau of 30 min). Since the lignin used is infusible, it is not necessary to carry out a stabilization treatment for carbonization, thus making the process even less expensive and faster than the processes with fusible lignin.

[0105] Such a process according to Examples 1 to 3 is easily transposable to the industrial scale.

Example 4 (Comparative)Use of Mixed Lignin Solutions (Water+Acetone) for Spinning

[0106] The same percentages of lignin and alginate as in Example 2 were resolubilized in solutions containing 5, 25, 50, 90% acetone. Under these conditions, it was impossible to obtain coagulation of the fiber in a 100 mM calcium chloride bath, thus showing the need to resolubilize the mixture exclusively in water.