EP2462235A2

EP2462235A2 - Process for producing sugars from lignocellulosic biomass involving a step of alcohol-alkaline delignification

Info

Publication number: EP2462235A2
Application number: EP10717481A
Authority: EP
Inventors: Karin Fackler; Kurt Messner; Chularat Krongtaew; Ortwin Ertl
Original assignee: Annikki GmbH
Current assignee: Annikki GmbH
Priority date: 2009-08-06
Filing date: 2010-04-30
Publication date: 2012-06-13
Also published as: CA2768159A1; CO6511213A2; US9970038B2; AU2010281334A1; CN102575268A; ECSP12011707A; RU2012108372A; BR112012002707A2; RU2617938C2; CA2768159C; AU2010281334B2; ZA201200989B; JP2013500727A; WO2011014894A2; MX350376B; TW201114907A; MX2012001450A; EP3121285A1; BR112012002707B1; US20180230503A1

Abstract

The invention relates to a method for producing carbohydrate cleavage products, characterized by the combination of the measures in which lignocellulosic material having an aqueous solution that contains an alcohol, in particular a C_1-4 alcohol or a phenol, and has a pH between 11.0 and 14.0 is treated in order to cleave lignocellulose and to remove cleavage products from the material, a material enriched with cellulose and hemicellulose being obtained, and the obtained material enriched with cellulose and hemicellulose being treated with at least one carbohydrate-cleaving enzyme in order to obtain the carbohydrate cleavage products.

Description

Process for the preparation of carbohydrate cleavage products from a lignocellulosic

material

The present invention relates to a process for the preparation of

Carbohydrate split products, in particular sugars, such as pentoses and hexoses, from a lignocellulosic material. The invention further relates to a process for the production of alcohol from the sugars. For the purposes of the present description and

Claims, the term "sugar" should also include "sugar oligomers".

In connection with the scarcity of crude oil and the discussion about grain as an energy supplier, the renewable raw material lignocellulose (straw, wood,

Paper waste, etc.) as a starting material for fuels or chemical products very important. Lignocellulose can be converted in two fundamentally different ways: 1) the "Thermochemical Platform", in which the lignocellulose is first gasified and the syngas is synthesized into desired products, and 2) the "Sugar Platform", where the main interest is in the Use of the bound in the polymers cellulose and hemicelluloses sugar, while lignin is still mainly used for energy. The present invention is to be associated with the second route.

In contrast to starch, the sugars of lignocellulose are present in tightly crosslinked, polymeric, crystalline structures of cellulose and hemicelluloses, which are additionally surrounded by a lignin coat, resulting in an extremely dense complex. The most obvious way to extract sugar from lignocellulose would be the direct use of cellulases and hemicellulases. However, this is made more difficult on the raw material straw or wood by the density of the above-mentioned complex. Due to their high molecular weight enzymes are unable to penetrate through the narrow pores in the lignocellulose. This means that a first step must be taken which increases the porosity of the lignocellulose and thereby allows further enzymatic saccharification.

This first step is referred to as "pretreatment" (pretreatment, digestion), which is very time-consuming, so that, for example, in the production of "second generation biofuels" up to 1/3 of the production costs have to be spent, which has a negative impact on profitability. The applied methods are aimed either at primarily liquefying the hemicelluloses (eg steam explosion, dilute acid-pretreatment) or at increasing the porosity by liquefying lignin (eg urn, ammonia-pretreatment).

The digested lignocellulose substrate can be treated enzymatically for the recovery of sugars or their oligomers, wherein the type of pretreatment can have a strong influence on the enzyme activity and the yield. At high

Reaction temperatures often give rise to toxic degradation products (for example furfural) which, in the case of an immediately connected ethanol fermentation, can inhibit the yeasts; see, for. Chandra et al., Advances in Biochemical Engineering / Biotechnology, 108: 67, 2007; Mansfield et al., Biotechnol. Prog. 15: 804, 1999.

These processes have the serious disadvantage that they are energy-consuming and run mainly at temperatures just below 200 ° C.

A technological improvement in this area, e.g. By developing low temperature processes (i.e., at a temperature below 100 ° C), significant progress in any material use of the raw material would be lignocellulose. This is the object of the present invention.

EP 1 025 305 B1 discloses a chemical process for lignin depolymerization (Cu system). It relies on the catalytic action of complexed copper in conjunction with hydrogen peroxide or organic hydroperoxides and is capable of oxidatively cleaving lignin at temperatures below 100 ° C. The used

Complexing agents are pyridine derivatives. Synthetic lignin models have been shown to cleave ether bonds of the lignin molecule when H ₂ O _{2 is used} as the oxidant, causing the lignin polymer to break down into oligomeric subunits. When using the Cu system with an excess of organic hydroperoxides, it is possible to delignify wood. The H ₂ O ₂ -based system appears to be better technically feasible, was used as a bleach additive in peroxide bleaching of kraft pulp and resulted in an improved delignification rate and higher whiteness.

Further, from "Oxidation of wood and its components in water-organic media", Chupka et al., Proceedings: Seventh International Symposium on wood and Pulping Chemistry, Vol. 3, 373-382, Beijing PR China, 25.-28. May 1993, that the efficiency of alkaline catalysis of the oxidation of wood and lignin increases considerably when an organic solvent, eg DMSO, acetone, ethanol, is added to the aqueous reaction medium, and the authors state that at pH values above 11 a sharp increase in the oxidation of wood and lignin takes place.

From WO 01/059204 a process for the production of pulp is known in which the starting material is subjected to a pretreatment, wherein the material is treated with a buffer solution and a delignification catalyst (transition metal). The delignification is carried out in the presence of oxygen, hydrogen peroxide or ozone.

In contrast, the inventive method for the production of sugars

characterized by the combination of measures that

- lignocellulosic material with an aqueous solution containing an alcohol, especially a C _I-4 - treated contains alcohol or a phenol and having a pH 11.0 to 14.0, to cleave lignocellulose and cleavage products from separating the material to obtain a cellulosic and hemicellulose enriched material, and

the resulting cellulosic and hemicellulose enriched material is treated with at least one carbohydrate-cleaving enzyme to recover the carbohydrate cleavage products.

Suitable alcohols are aliphatic or cycloaliphatic, monohydric or polyhydric alcohols or phenols, eg. B. Ci _-6 - alcohols, in particular a such as methanol, ethanol, propanol and butanol, including their isomers; Glycols (ethanediols, propane, butane, pentane, hexanediols), glycerol, propenol, butenol, cyclopentanol, cyclohexanol, benzyl alcohol; or phenols, such as phenols, cresols, catechols, naphthols, but also amino alcohols, such as ethanolamine, methanolamine and hexanolamine. Preferred is a C _1-4 alcohol. For the purposes of the present patent application, phenols are disclosed in U.S. Patent Nos. 5,429,648, 4,329,688, 4,348,359, and 5,348,347

Generic term "alcohol" included.

The alcoholic solution of the lignin extract also offers agreeable options in the further processing of the lignin or xylan cleavage products.

Alcohol is in an aqueous solution in the inventive method preferably in an amount of 10 to 70 vol%, z. B. 20 to 50 vol%, preferably from 30 to 40 vol% before.

In the process according to the invention, the lignocellulosic material is preferably present in the aqueous solution in a consistency of 3-40% by weight, such as 5-40% by weight, in particular 5-20% by weight.

Preferably, the lignocellulose is at a temperature of below 100 ° C, such as below 80 ° C, z. B. cleaved below 60 ⁰ C.

The pH can be adjusted with a base, preferably an inorganic base, for example sodium hydroxide solution.

The present invention is based on the realization that a with an aqueous basic solution containing an alcohol, especially a Ci _-4 - containing alcohol or phenol, and having a pH of 11.0 to 14.0, treated lignocellulosic Material can be processed enzymatically in higher yield to carbohydrate cleavage products, such as sugars, as a delignified in any other way material, in particular without the addition of alcohol.

As carbohydrate cleavage products mainly pentoses and hexoses are formed.

Preferred sugars include xylose and glucose. A preferred embodiment of the method according to the invention is characterized in that the cellulosic and hemicellulose-enriched material is treated with a xylanase and a cellulase to recover the sugars.

As lignocellulosic material is preferably straw, energy grasses, such. B.

Switchgrass, elephant grass or abaca, sisal, bagasse, or atypical

Lignocellulosic substrates such as husks, e.g. Rice husks, preferably straw, energy grasses bagasse or husks, particularly preferably straw or bagasse, z. As straw used. Straw has a highly hydrophobic surface, so wetting with aqueous solutions is a problem. It has been found that it is possible by the use of alcohol, even without pressure to introduce the reaction solution into the pores of the substrate and to replace the existing air by reaction solution. It has also been shown that alcohol accelerates the extraction of the cracking products from straw and helps to keep the lignin cleavage products in solution. Furthermore, it has been shown that, in contrast, alcohol reduces the solubility of the hemicellulose and its cleavage products and thus the hemicellulose is held in the substrate.

By pressing the liquid phase from the substrate after the digestion process, the substrate concentration is increased, so that smaller amounts of enzyme to the enzymatic

Hydrolysis, or in other enzymatic processing are required.

In alcohol production, enzyme costs are a crucial cost factor.

Alcohol leads to the fact that the solubility of the hemicelluloses possibly released in the alkaline range during the reaction, in addition to the lignin, and their cleavage products are greatly reduced and these remain bound to the substrate. The advantages for the process are high selectivity of the Ligninabbaus, in the case of a separation of the

Extraction solution from the solid a very low concentration of hemicellulose and their cleavage products in the extraction solution, because the hemicellulose remains in the

Solid content and thereby obtained for enzymatic hydrolysis and sugar extraction.

The alcoholic solution of the lignin extract also offers improved possibilities in the further processing of the lignin and the production of products from lignin. It has also been found that the use of alcohol, in particular a C4 alcohol or a phenol, in the alkaline digestion below 100 ° C, the degradation of hemicelluloses is largely prevented, so that almost all of the hemicellulose for further enzymatic cleavage and conversion xylose is available for higher value products and not, as with other processes, partly in

Digestion is degraded and obtained as a lignin / sugar mixture.

The delignification carried out in the digestion increases the porosity of the cell walls of the lignocellulosic material, for example in the case of straw, to such an extent that almost all xylose becomes accessible to the xylanase and approximately 100% of the xylan hydrolyzed and xylose can be recovered. This makes the process according to the present invention particularly suitable for producing higher-value products in conjunction with an enzymatic conversion of the xylose. The enzymatic conversion can take place either directly in the mixture of xylose solution and solid, or else with the xylose solution separated off from the solid.

In another, after the enzymatic hydrolysis of xylan and the

According to the invention conversion of xylose to xylitol following alcohol production from the remaining solid, enzyme costs are a crucial cost factor. These also partly result from unspecific binding of enzymes to the lignin, see, for example, Chandra et al, 2007, ibidem. The partial removal of lignin reduces this loss of activity and has a cost effective.

The advantages for a subsequent enzymatic process are, for example, that from the high selectivity of lignin degradation with almost complete preservation of the sugar polymers a very low concentration of hemicellulose and their cleavage products in the

Extraction solution results, the hemicellulose remains in the solid content and thus for the enzymatic hydrolysis and sugar extraction and their further conversion is obtained. This results according to the invention a maximum substance utilization rate and, for example in conjunction with the use of xylose dehydrogenases, high profitability of

described process. Performing a xylose conversion process to xylitol may be followed

enzymatic release of xylose directly in the solid solution mixture obtained according to the present inventive method, which further increases the profitability of the overall process.

In the case of conversion to xylitol, the residual alcohol remaining in the substrate after pressing the solid can be used directly as a substrate for the decomposition process

Alcohol dehydrogenase can be used for the regeneration of NAD to NADH. If the process is designed so that the residual alcohol remaining in the reaction mixture is (partially) consumed from the digestion, an alcohol removal from the

Product solution (partially) superfluous and thus the efficiency of the overall process further increased.

In the case of conversion of the lignin cleavage products, the alcohol acts as a radical scavenger and solvent for cleavage products from enzymatic, biomimetic or chemical depolymerization of the higher molecular weight lignin cleavage products

low molecular weight.

The low proportion of hemicelluose and their cleavage products in the extract and the increased solubility of lignin, increase the throughput rates in a separation of the solid from the conversion products, as well as their processing by filtration.

The inventive method allows, for example, the separation of the three

Main components of straw, namely glucose, xylose and lignin in very low-contaminant streams and their further conversion to higher-value products, such as xylitol, and thus meets the requirements of an ideal biorefinery process.

Another advantage of the method according to the invention compared to others

Digestion, which occur predominantly in the temperature range between 150 ° C and 200 ⁰ C, is its reaction temperature below 100 ° C. The low energy consumption allowed It is important to use the lignin obtained during digestion not as an energy source for the digestion process, but as a valuable substance.

After treatment with the aqueous solution containing an alcohol, in particular a C _1-4 -alkyl or phenol, and H ₂ O ₂ , the lignin-containing solution is separated off according to the method of the present invention, and the digested solid is preferably co-precipitated a xylanase, e.g. B. 6-72 hours at 30-90 ° C and the liquid phase separated from the solid, whereupon the liquid phase to

Derived products, eg. B. xylitol is further reacted.

The remaining after separation of the liquid phase solid is preferably treated with cellulase, which can be obtained by further fermentation of the solid / glucose solution, ethanol, butanol or other fermentation products; or the remaining solid is subjected to a thermal or thermochemical material conversion and the resulting products, such as fuel components, fuel additives and / or other chemical products, such as. As phenols are separated; or the remaining solid is subjected to microbial conversion by bacteria, yeasts or fungi; or the remaining solid is subjected to a further delignification step for the purpose of obtaining a cellulosic fibrous material.

The remaining solid can be fermented in a biogas plant and biogas

be further processed.

One of the most economically interesting derivatives of xylose is xylitol.

The main sources of xylose recovery are pulping liquors from the pulp industry, which contain a wealth of degradation products, mainly lignin and hemicellulose, so that xylose must first be obtained through laborious separation and purification steps. So describes z. BH Harms in "Welcome to the natural world of Lenzing, world leader in cellulose fiber technology", autumn conference of the Austrian paper industry, Frantschach (15. 11. 2007) the extraction of xylose from the caustic solution by gel filtration, a technically very complex method usually not for Bulk products application finds. The thus obtained xylose is then catalytically converted to xylitol.

In a further aspect, the xylose obtained according to the present invention is fermentation-free converted into xylitol by reaction with a xylose reductase, e.g. B. a xylose dehydrogenase, for example from Candida tenuis, wherein optionally a xylose reductase and optionally a co-substrate for the regeneration of the co-factor and optionally alcohol dehydrogenase and optionally NAD (P) H is added to the xylose solution; in particular, wherein the obtained xylitol by filtration of the

Ligninspaltprodukten is separated.

With the following Example 1 and Comparative Example IA, the influence of

Pretreatment in the presence of alcohol on the yield of reducing sugars after enzymatic hydrolysis is documented.

example 1

Pretreatment of wheat straw

Wheat straw is crushed to a particle size of about 2 cm. 5 g crushed

Wheat straw is suspended in a 500 mL reaction vessel in 200 mL of a solution consisting of 49.5% water, 50% ethanol and 0.5% hydrogen peroxide. The suspension is heated to 50 ° C. in a water bath, thermostated and the pH of the suspension is adjusted to a starting pH of 12 using aqueous NaOH solution. The mixture is continuously magnetically stirred at 200 rpm, 60 ° C. for 24 hours. Thereafter, the solid content is filtered off and washed with distilled water II.

For enzymatic hydrolysis, 100 mg pretreated substrate of each parallel experiment was adjusted to pH 4.8 with 9.8 ml of 50 mM Na acetate buffer and admixed with 200 μl of Accellerase 1000 Suspension (www.genencor.com). Accellerase is an enzyme mixture of cellulases and hemicellulases. The enzymatic hydrolysis was carried out at 50 ^° C. in a shaking water bath. The soluble monomers of hexoses and pentoses released after 48 hours were determined in the form of reducing sugars by the DNA method (Miller et al., Analytical Chemistry 31 (3): 426, 1959) in 1 mL of liquid supernatant, weighed out to the amount pretreated Substrate and expressed in percent of the maximum theoretical yield.

The theoretical maximum yield of reducing sugars was determined separately and is 705 mg +/- 5% per g of untreated straw.

For each test batch, 5 parallel experiments were carried out. The yield of reducing sugars was 99% +/- 4%.

Comparative Example IA

Example 1 was repeated, but without the addition of alcohol. The yield

reducing sugars was only 64% +/- 3%.

Example 2

Pretreatment of wheat straw

Wheat straw is crushed to a particle size of about 2 cm. 2.5 g of crushed wheat straw is suspended in 200 mL of a solution consisting of 49.5% water and 50% isopropanol in a 500 mL reaction vessel. The suspension is at 50 ° C in Heated, thermostated and the pH of the suspension with aqueous NaOH solution to a starting pH of 13 (or 14) adjusted. The mixture is continuously magnetically stirred at 200 rpm, 60 ^° C. for 24 hours. After that, the

Solids were filtered off and washed with distilled water II.

For enzymatic hydrolysis, 100 mg pretreated substrate of each parallel experiment was adjusted to pH 4.8 with 9.8 ml of 50 mM Na acetate buffer and admixed with 200 μl of Accellerase 1000 Suspension (www.genencor.com). Accellerase is an enzyme mixture of cellulases and hemicellulases. The enzymatic hydrolysis was carried out at 50 ° C in a shaking water bath. The soluble monomers of hexoses and pentoses released after 48 hours were determined in the form of reducing sugars by the DNA method in 1 mL of liquid supernatant, pre-treated to the amount weighed out

Substrate and expressed in percent of the maximum theoretical yield.

In each case 5 parallel experiments were carried out per test batch. The yields of reducing sugars was 97% +/- 4%.

Example 3

Enzymatic xylitol production from a xylose solution prepared from straw according to the method described in Example 2. As a cosubstrate is

Isopropanol used.

The reaction solution contains 5 mg / mL xylose.

Xylose reductase (XR) from Candida tenuis reduces xylose to xylitol. This XR requires as coenzyme NADH (nicotinamide adenine dinucleotide reduced), which is oxidized in the reaction to the coenzyme NAD ⁺ . The regeneration of the oxidized cofactor is carried out by parallel activity of an alcohol dehydrogenase (ADH: enzyme-linked regeneration). Isopropanol is used as the co-substrate. Isopropanol and NAD ⁺ are converted by the ADH to NADH and acetone as shown in Reaction Scheme 1: REACTION SCHEME 1

Xylose _{NADH + H +} NAD ⁺ xylitol

isopropanol

acetone

Table 1 shows the reaction ratios in the 5 different experimental reactions # 049, # 050, # 051, # 052, # 053 and # 054:

Table 1

Total volume: 1 mL

Temperature: 26 ± 2 ^° C Magnetic stirrer: 200 rpm

Time: 15 hours

To deactivate the enzymes, all samples were heated to 95 ° C for 15 minutes and centrifuged in preparation for subsequent HPLC analysis.

Analysis - HPLC:

Column SUGAR SP0810 + Pre-column SUGAR SP-G

Detector: refractive index detector

Eluent: deionized H ₂ O

Flow: 0.75 mL / min

Sample amount: 10 μL

HPLC quantification precision: ± 10%

Retention time:

Xylose: 13.97 min

Xylitol: 37.73 min

Isopropanol: 16.69 min

Acetone: 16.54 min

Results:

The substrate concentration of sample # 049 was determined by HPLC to be 0.9 mg / mL.

Reaction mixture # 050 contains only xylose reductase (0.1 U / mL) and NADH (1 mM). After the 15 hour reaction, 0.085 mg of xylose was consumed. The xylitol concentration was below the detection limit.

Reaction # 052 is similar to Reaction # 050, but with the difference that the regeneration system is used here. It comes to the total sales of

used xylose. Concentrations used: XR (0.1 U / mL), NADH (1 mM), ADH (0.25 U / mL) and isopropanol (5%). The xylose concentration of sample # 053 was determined to be 2.121 mg / mL, which corresponds to the expected xylose concentration.

Reaction # 054 is similar to Reaction # 052, but involves a factor of 2 increased xylose start concentration (50% substrates in the reaction). The concentration of xylitol produced was measured with 0.945 mg of xylitol. Used concentrations: XR (0.1 WmL), NADH (1 mM), ADH (0.25 U / mL) and isopropanol (5%).

Table 2 summarizes the results of the reactions based on HPLC data (xylose consumed and xylitol recovered; "u.D.L." means "below the detection limit"):

Table 2

Example 4

Enzymatic xylitol production from a xylose solution made from straw after im

Example 2 was prepared. The cosubstrate used is ethanol.

The volume of the substrate solution was reduced to 50% (see Example 2) using a rotavapor to increase the xylose concentration (~10 mg / mL xylose).

The regeneration of the oxidized cofactor was carried out by the activity of the candida tenius xylose reductase (XR) used and the additional activity of an aldehyde dehydrogenase from Saccharomyces cerevisiae used (Sigma-Aldrich: catalog number A6338; (EC) Number: 1.2.1.5; CAS Number: 9028-88-0). These are both about a substrate-coupled as well as an enzyme-coupled reaction. The cosubstrate used is ethanol. Ethanol and NAD ⁺ are converted in the first step by the activity of the XR to NADH and acetaldehyde. In the second step, acetaldehyde and NAD ⁺ by the activity of aldehyde dehydrogenase (AIdDH) to acetate implemented (see to Sigma-Aldrich: catalog number A6338; and "Characterization and Potential Roles of Cytosolic and Mitochondrial aldehyde dehydrogenases in ethanol Metabolism in.

Saccharomyces cerevisiae ", Wang et al., Molecular Cloning, 1998, Journal of Bacteriology, pp. 822-830). Per mol of cosubstrate reacted would in this case be 2 moles

Reduction equivalents (NADH) are formed (see Reaction Scheme 2).

REACTIVE SCHEME 2

CH ₃ COO ^■

Essigsäureanion

Table 3 shows the reaction conditions of the 4 different reaction reactions 247, 249, 250 and 253. There were different ethanol concentrations and AldDH concentrations used. The cofactor and substrate concentrations were kept constant.

Table 3

Total volume: 0.5 mL

Temperature: 25 ± 2 ° C

Thermomixer: 500 rpm

Time 112 hours

To deactivate the enzymes, all samples were heated to 70 ^° C. for 15 minutes and centrifuged and filtered (PVDF, 0.2 μm) in preparation for subsequent HPLC analysis.

Analysis - HPLC:

Column SUGAR SP0810 + Pre-column SUGAR SP-G

Column temperature: 90 ° C

Detector: refractive index detector

Eluent: deionized H ₂ O

Flow: 0.90 mL / min

Sample amount: 10 μL

HPLC quantification precision: ± 10% Results:

The maximum yield (reaction 249) could be achieved with an ethanol concentration of 1.2 mol / L. A total of 1.38 mg / mL xylitol was produced, which corresponds to a yield of 21.2% of theory of xylitol.

Table 4 summarizes the results of the reactions based on the HPLC measurement data.

Table 4

From the results, it can be seen that ethanol can be used as a cosubstrate. As can be clearly shown by comparing the reaction 249 (reaction mixture includes AldDH) and 253 (reaction mixture without AldDH), the addition of the aldehyde dehydrogenase leads to a significant increase in the yield of xylitol. The difference in converted xylose to xylitol is ~ 8%. This result, in conjunction with the abovementioned references, only allows the conclusion that AldDH further oxidizes the acetaldehyde formed in the first partial reduction to acetic acid (cf.

Reaction scheme 2). This energetically favorable reaction and the concomitant increased concentration of NADH shifts the equilibrium of the educt towards the product xylitol in the first partial reaction.

Claims

claims

1. A process for the preparation of carbohydrate split products, in particular sugars, characterized by the combination of the measures that

lignocellulosic material is treated with an aqueous solution containing an alcohol, in particular a C 1 -C 4 alcohol or a phenol, having a pH between 11.0 and 14.0, to cleave lignocellulose and fission products from the material Separate, with one with cellulose and

Hemicellulose-enriched material is obtained, and

- The obtained, enriched with cellulose and hemicellulose material with

at least one carbohydrate-cleaving enzyme is treated to the

To win carbohydrate cleavage products.

2. The method according to claim 1, characterized in that the aqueous solution has a pH between 11.0 and 13.0.

3. The method according to any one of claims 1 or 2, characterized in that the

Cleavage takes place at a temperature of less than 100 ° C,

4. The method according to claim 3, characterized in that the cleavage in a

Temperature is below 40 ° C,

5. The method according to one of Ansprüpche 1 to 4, characterized in that as

lignocellulosic material straw, bagasse, energy grasses and / or husks is used.

6. The method according to any one of claims 1 to 5, characterized in that the

lignocellulosic material is present in the aqueous solution in a consistency of 5-40% by weight.

7. The method according to any one of claims 1 to 6, characterized in that the cellulosic and hemicellulose-enriched material is treated with a xylanase and / or a cellulase to recover the sugars.

8. The method according to any one of claims 1 to 7, characterized in that the

obtained sugar are fermented to alcohol, which is separated and recovered.

9. The method according to any one of claims claim 1 to 8, characterized in that the digested solid reacted with a xylanase and the resulting

Liquid phase reacted to xylitol, and the remaining solid

- Is further reacted with cellulase to obtain various fermentation products; or

- subjected to a thermal or thermochemical conversion;

or

is subjected to microbial transformation by bacteria, yeasts or fungi;

or

- Is subjected to a further delignification step for the purpose of obtaining a cellulose fiber material.

10. The method according to claim 9, characterized in that the digested solid reacted with a xylanase and the resulting liquid phase by xylose

Dehydrogenase reacted to xylitol, and the remaining solid

- Is further reacted with cellulase to obtain various fermentation products; or

- subjected to a thermal or thermochemical conversion;

or

is subjected to microbial transformation by bacteria, yeasts or fungi;

or

11. The method according to any one of claims 9 or 10, characterized in that the after separation of the (fermentation) products remaining solid fermented in a biogas plant and processed into biogas.