Hydrolysis of cellulosic fines in primary clarified sludge of paper mills and the addition of a surfactant to increase the yield

Abstract

A method for processing a stream of cellulosic fines containing inorganic particles, to increase a hydrolysis yield of polysaccharide degradation enzymes, such fines in a waste stream from a recycled packaging paper mill to produce a stream of fermentable sugars, comprising treating the fines with a surfactant which selectively binds to the inorganic particles and which reduces binding to the inorganic particles by the polysaccharide degradation enzymes, and degrading polysaccharides in the waste stream with the polysaccharide degradation enzymes.

Claims

1. A method for processing a stream of cellulosic fines rejected from a repulped old corrugated containerboard process for recycling old corrugated containerboard, containing cellulosic fines, and a remainder of 25-65% by oven dry weight of solids being ash-producing components including inorganic particles comprising at least one of calcium carbonate and kaolin, having an affinity for polysaccharide degradative enzymes and reducing the activity of the polysaccharide degradative enzymes in degrading the cellulosic fines, comprising: adding at least one polysaccharide degradative enzyme to the stream; adding at least one non-ionic surfactant to the stream in an amount of between 3% and 11% based on the oven dry weight of the stream, adapted to selectively bind surfaces of the at least one of calcium carbonate and kaolin to reduce affinity for the polysaccharide degradative enzymes without inactivating the polysaccharide degradative enzymes, to thereby increase a hydrolytic activity of the at least one polysaccharide degradative enzyme on the cellulosic fines as compared to an absence of the at least one non-ionic surfactant; and maintaining a solution comprising the cellulosic fines, inorganic particles, at least one non-ionic surfactant, and at least one polysaccharide degradative enzyme for a sufficient period of time to degrade at least a portion of the cellulosic fines into fermentable sugars.

2. The method according to claim 1, further comprising receiving the stream of cellulosic fines as a rejected waste stream from a repulped old corrugated containerboard (OCC) mill.

3. The method according to claim 1, wherein the inorganic particles comprise calcium carbonate.

4. The method according to claim 1, wherein the inorganic particles comprise precipitated calcium carbonate.

5. The method according to claim 1, wherein the inorganic particles comprise kaolin.

6. The method according to claim 1, wherein the at least one polysaccharide degradative enzyme comprises at least one of a cellulase and a hemicellulase.

7. The method according to claim 1, wherein the at least one non-ionic surfactant comprises polysorbate.

8. The method according to claim 1, wherein the at least one non-ionic surfactant comprises polysorbate 80.

9. A method for enzymatically hydrolyzing a mixed stream from a repulped old corrugated containerboard process, comprising cellulosic fines separated from pulp suitable for recycling, containing primarily cellulose and hemicelluloses, and a remainder of 25-65% by oven dry weight of solids as ash-producing constituents including inorganic particles comprising at least one of calcium carbonate and kaolin, having a competitive binding affinity for hydrolytic enzymes, comprising: adding at least one hydrolytic enzyme to the mixed stream; adding at least one non-ionic surfactant to the mixed stream in an amount of between 3% and 11% based on the oven dry weight of the mixed stream, to decrease a binding affinity of the at least one hydrolytic enzyme for the inorganic particles and thereby increase a hydrolytic activity of the at least one hydrolytic enzyme as compared to an absence of the at least one non-ionic surfactant on the cellulosic fines; and hydrolyzing the cellulosic fines with the hydrolytic enzyme.

10. The method according to claim 9, further comprising receiving the mixed stream from a repulped old corrugated containerboard (OCC) mill as rejected material after separation of cellulose fibers for recycling.

11. The method according to claim 9, wherein the inorganic particles comprise calcium carbonate.

12. The method according to claim 9, wherein the inorganic particles comprise precipitated calcium carbonate.

13. The method according to claim 12, wherein the inorganic particles further comprise kaolin.

14. The method according to claim 9, wherein the at least one hydrolytic enzyme comprises at least one of a cellulase and a hemicellulase in an amount of at least 10 FPU (filter paper units).

15. The method according to claim 9, wherein the at least one non-ionic surfactant comprises polysorbate.

16. The method according to claim 9, wherein the at least one non-ionic surfactant comprises polysorbate 80.

17. The method according to claim 9, wherein: the at least one non-ionic surfactant and the at least one hydrolytic enzyme are added as a mixture to the mixed stream; and the cellulosic fines are hydrolyzed with the hydrolytic enzyme in an incubator, to produce a solution comprising fermentable sugars from the hydrolyzed cellulosic fines.

18. A method for enzymatically hydrolyzing cellulosic fines in a mixed stream from an old corrugated cardboard recycling process in which the cellulosic fines are separated from pulp for recycling, with at least one hydrolytic enzyme, the mixed stream comprising cellulosic fines containing lignin and a remainder of 25-65% by oven dry weight solids as ash producing inorganic particles comprising at least one of calcium carbonate and kaolin, comprising: adding at least one non-ionic surfactant to the mixed stream in an amount of between 3% and 10% based on the oven dry weight of the mixed stream, to selectively reduce an affinity of at least one hydrolytic enzyme for the at least one of calcium carbonate and kaolin and to selectively increase a hydrolytic activity with respect to the cellulosic fines of the at least one hydrolytic enzyme as compared to an absence of the at least one non-ionic surfactant; adding the at least one hydrolytic enzyme to a solution containing the mixed stream of cellulosic fines and inorganic particles and the at least one non-ionic surfactant; and hydrolyzing the cellulosic fines with the at least one hydrolytic enzyme.

19. The method according to claim 18, wherein the inorganic particles comprise calcium carbonate, the at least one non-ionic surfactant comprises polysorbate and the at least one hydrolytic enzyme comprises at least one of a cellulase and a hemicellulase.

20. The method according to claim 18, wherein the at least one hydrolytic enzyme comprises at least one of a cellulase and a hemicellulase, the inorganic particles having a competitive binding affinity for the at least one hydrolytic enzyme comprise precipitated calcium carbonate, and the at least one non-ionic surfactant comprises a polysorbate surfactant, further comprising: separating the inorganic particles from a hydrolysate formed during the hydrolyzing; and fermenting fermentable sugars in the hydrolysate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows hydrolysis yield of synthetic substrate of varying composition after addition of different concentration of surfactant (Tween80) and enzyme.

(2) FIG. 2 shows hydrolysis yield of synthetic substrate of Calcium Carbonate (15%) after addition of different concentration of surfactant (Tween80) and enzyme.

(3) FIG. 3 shows hydrolysis yield of screw press fines with addition of different concentrations of surfactant (Tween 80)

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(4) Hydrolysis experiments were conducted on two different feedstocks. The first was a simulated waste feedstock, consisting of a sample of unbleached kraft softwood pulp (UBSWKP) that is typical of repulped old corrugated containerboard stocks (OCC). The second was an actual reject fines waste stream from a recycled paper board mill. (Supplied by Minimill LLC, Dewitt N.Y. in conjunction with Greenpak LLC, Niagara Falls N.Y.). The reject stream consisted of cellulosic fines (35%) with the remainder as ash-producing constituents. The non-cellulosic portion contains kaolin and precipitated calcium carbonate fillers from the waste paper and smaller amounts of plastic and other residues.

(5) The non-cellulosic portion of the feedstock acts a competitor for enzyme adsorption, and reduces the net yield and productivity of the hydrolysis per unit enzyme reactant. This leads to increased costs and inefficiencies in the hydrolysis process.

(6) Table 2 below shows the enzymatic hydrolysis yields of a sample of waste fines solids from a recycled paper mill. Although the yields are relatively low, an increase would be expected upon routine optimization with respect to enzyme dosages.

(7) The present approach to resolve this problem is to preferentially or selectively cover the inorganic components with a suitable surfactant so that enzyme binding and action is localized to the cellulosic components. For this purpose, cationic, non-ionic and anionic surfactants were tested at different dosages.

(8) Results are shown for the case of the nonionic surfactant. The ionic surfactants tested were not seen as being as effective as the nonionic surfactant.

(9) TABLE-US-00002 TABLE 2 Enzymatic hydrolysis of paper mill waste (recycled paper mill, fines from screw press). EH 3 days yield increase surfactant w/o based on Fines (% on EH surfac- standard No. FPU fines) yield Average tant increase EH 1 10 3  8.1% 2 10 3  6.2%  7.2%  3.1%  4.1% 131.0% 3 10 10  6.7% 4 10 10  4.9%  5.8%  3.1%  2.7%  86.9% 5 25 3 25.3% 6 25 3 24.6% 25.0% 14.8% 10.2%  68.9% 7 25 10 25.4% 8 25 10 22.8% 24.1% 14.8%  9.3%  62.9%

(10) A pulp sample (unbleached kraft softwood pulp) was chosen as a model of the OCC pulp. FIG. 1 below shows the hydrolysis yield when a mixture of surfactant and enzyme was applied to this sample mixed with fillers. Hydrolysis yield was defined as the mass of cellulose dissolved (by the action of the enzyme) to the original (oven dry) mass of the sample. Different dosages of the enzyme are represented on the abscissa by FPU. The surfactant added was Tween 80, a polysorbate nonionic carbohydrate based detergent.

(11) ##STR00001##

(12) FIG. 1 shows that the addition of the surfactant increases the hydrolysis yield when the enzyme activity is greater than 10 FPUs. The untreated calcium carbonate filler suppresses enzyme hydrolysis, whereas the kaolin filler is more benign to the action of the enzymes. FIG. 2 shows the hydrolysis yield as a function of dosage of the surfactant with enzyme loading chosen as 20 FPUs. The maximum effect surfactant dosage appears to be close to 7% based on the oven dry weight of the biomass. FIG. 3 shows that the hydrolysis yield of mill waste rejects containing fines also increases with the addition of the same nonionic detergent.

(13) The numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

(14) TABLE-US-00003 TABLE 3 Characterization of Fines Physical characteristics of waste solids from a recycled paper mill. Parameter Value pH 6.4 Solid content 52% Particle size 2.1-3μ Zeta Potential −9 mV Ash content % solids Total 33% Calcium Carbonate 15% Other fillers and 18% residuals

(15) TABLE-US-00004 TABLE 4 Properties of Non-ionic surfactant (Polysorbate 80) Polyelectrolytes: Tween 80 Property Value Unit Charge Non-ionic Critical Micelle 0.01 (mM) Concentration HLB 15 Surface tention 16 (dyne/cm) Molecular weight 1310 Dalton