WO2011061400A1

WO2011061400A1 - Method of processing a carbohydrate raw-material

Info

Publication number: WO2011061400A1
Application number: PCT/FI2010/050933
Authority: WO
Inventors: Anne Kallioinen; Satu Vuorela; Niklas Von Weymarn; Jaana Uusitalo; Matti Siika-Aho; Tiina Riekkola; Timo Repo; Markku Leskelä; Petro Lahtinen; Maija Hakola
Original assignee: Valtion Teknillinen Tutkimuskeskus
Priority date: 2009-11-18
Filing date: 2010-11-18
Publication date: 2011-05-26
Also published as: FI20096199A0

Abstract

The present invention relates to a method of fractionating lignocellulosic biomass into at least one cellulose rich solid fraction and at least one liquid fraction, wherein an alkaline agent and water are added to the biomass to form a mixture and the biomass is contacted in the mixture with an oxidizing agent until most of the lignin is solubilised to produce a solid fraction comprising a cellulosic material having a reduced content of lignin and a liquid fraction comprising dissolved lignin. The method of invention is particularly useful for processing and pre-treating lignocellulose containing biomass e.g. for the production of chemicals and for other non- fibrous applications.

Description

METHOD OF PROCESSING A CARBOHYDRATE RAW-MATERIAL

Field of the Invention The present invention relates to modification of biomass. In particular, the present invention relates to methods of processing and pre-treating lignocellulose containing biomass e.g. for the production of chemicals and for other non- fibrous applications.

Description of Related Art

Conversion of biomass to value-added products, especially to different forms of energy has received growing attention as a mean of replacing energy and other end-products derived from fossil raw materials. For instance, of the conventional biofuels for transport (ethanol, ETBE, pure vegetable oil, biodiesels and bio methane), ethanol has a long proven history and in some cases also environmental advantages compared to fossil fuels. In addition, biomass is considered a major renewable source for bulk chemicals and materials.

Biomass can also be converted into various chemicals by fractionating processes yielding its components either in native or modified (e.g. hydrolysed or oxidized) form. The mixture of components obtained by such a conversion can be used as chemicals as such or after further processing. The further processing methods can be physical (e.g. fractionation and separation), chemical (e.g, use of components as raw materials for synthesis or chemical modifications) or biochemical (e.g. fermentation processes or enzymatic modification). By this way it is possible to utilize all the most abundant components of biomass: cellulose (or glucose derived from it), hemicellulose (or sugars or

oligosaccharides derived from it), lignin (or its fragments) and minor biomass components depending on the specific raw materials used (e.g. proteins, pectins, extractives), and their degradation products. Chemicals, including ethanol can be produced from a variety of renewable raw materials by fermentation processes. This is done using a procedure known as the sugar route: the carbohydrate polymers of the biomass are first hydrolysed to monosaccharide sugars, and these are then in a second stage further converted to ethanol or other products by micro organisms. Traditionally, for example ethanol has been produced from starch or sugar- containing agricultural crops but currently it is seen that utilization of different raw materials rich in lignocellulose will be pre-requisite for large scale bio fuel production. Suitable lignocellulose rich raw materials include agricultural and forestry residues, side streams from food and forest industries, municipal and industry wastes, as well as energy crops. These "second generation" raw materials (lignocellulosics) combined with efficient technologies to convert these into ethanol are expected to decrease the carbon dioxide footprint of ethanol production, besides widening the raw material basis and possibly improving the economics of production, Conversion of biomass into ethanol or other chemicals via the sugar route is a biotechnical process. In a sequence of catalytic reactions micro-organisms (typically yeast) convert sugars (preferably glucose or sucrose) into ethanol and by-products such as carbon dioxide. In conventional ethanol production the sugars are obtained by simply pressing out the sucrose-rich juice from e.g. crushed sugar cane and sugar beet. Alternatively, starch is hydro lysed in the presence of cheap enzymes and moderate heat increase to a glucose-rich solution. The structure of hgnocellulosic materials is, however, much more complex, and a release of the sugars requires much harsher processing. Enzymes are typically chosen to perform the main hydrolysis of available polysaccharides in lignocellulose. However, before enzymes can work efficiently the Hgnocellulosic material must first be pre-treated by breaking down or modifying the native structure of lignocellulose. Several such methods are known in the art. These include steam explosion, with or without chemicals, such as sulphuric acid, ammonia (AFEX), etc., hot water treatment, mild acid hydrolysis, CaO treatment, wet oxidation, organic solvent treatment, ammonium treatment, etc. To give some examples of known solutions, the following documents are cited:

International Patent Application WO 94/03646 discloses methods for the pre-treatment of lignocellulose-containing biomass comprising the addition of calcium hydroxide and water to the biomass and subjecting the mixture thus formed to relatively high temperatures for a period of time sufficient to render the biomass amenable to digestion.

WO1994/003646 (Holzapple et al.). describes a method of pretreating.lignin containing biomass to render the biomass amenable to digestion. In the method water and calcium hydroxide and optionally oxygen containing gas are added to the biomass at a temperature of 40 tol50 °C and an elevated pressure at a pH between 8,5 and 10.5. The aim of the known method is achieve oxidation without degradation of the lignocellulose.

WO2004/081185 (Burdette et al.) describes methods of hydrolyzing lignocellulose at mild or moderate conditions, such as at a temperature of about 10 to 90 °C and a pH of about 4.0 to 10.0. A treatment using e.g. sodium percarbonate or Na₂CC"3 in a pre-treatment step is shown to increase sugar yield when compared to sole enzymatic treatment. A wide range of oxidizing agents, including hydrogen peroxide, sodium and calcium hypochlorite and potassium permanganate, are used in the examples.

The main difficulties associated with existing techniques are incomplete decomposition or modification of the lignocellulosic material and the formation of toxic compounds during pre-treatment, which makes the further processing less feasible and efficient. In particular, the crude hemicellulose or cellulose filtrate from conventional pretreatment contains usually various degradation products of lignocellulose. These can be lignin and sugar decomposition products, including furfural, hydroxymethyl furfural and formic and acetic acid. Most of these components are toxic to enzymes and microorganisms and will slow any subsequent hydrolysis and fermentation process. Ineffective enzymatic hydrolysis step reduces the process economy remarkably.

An improved pretreatment method is disclosed in our previous International Patent Application No. WO2009/034235 which describes a way of processing carbohydrate raw- material for use in non- fibrous applications wherein the lignocellulosic raw-material is treated in the presence of transition metal catalyst with an oxygen-containing gas under elevated pressure and temperature.

Summary of the Invention

It is an aim of the present invention to provide a novel method for processing

carbohydrate-rich raw material of plant, especially wood origin so as to provide, for example, an improved starting material for production of ethanol or other chemicals. It is another aim of the present invention to provide an alternative method of fractionating a lignocellulosic feedstock to produce novel aqueous suspensions containing a solid fraction and dissolved carbohydrates and lignin. The invention is based on the finding that by subjecting cellulosic or lignocellulosic raw- material, optionally after size reduction and slurrying with liquid, to a treatment carried out in an alkaline aqueous medium, selected from alkali metal hydroxides, carbonates and percarbonates, in the presence of oxygen, a fibrous fraction can be obtained which can be surprisingly easily hydro lyzed with enzymes. Further, partial or even total hydrolysis of the material can be achieved at least essentially without harmful generation of toxic byproducts which accompanies the performance of traditional pre-treatment processes. Thus a second fraction is obtained which comprises dissolved lignin and carbohydrates.

It should be pointed out that none of the references cited above proposes a non-catalytic method comprising using a combination of an alkali metal hydroxide or carbonate, or percarbonate, to provide an alkaline environment having a pH typically in excess of 11.5, a pressurized gas containing oxygen in hydrolysis of lignocellulosic raw-materials under conditions sufficient for dissolving most of the lignin preparatory to produce at least one fraction particularly well suited for non-fibrous applications.

According to the present invention, the raw material treated in alkaline slurry in the presence of oxygen gives rise to a suspension of solids and dissolved components. The suspension, or at least a part thereof, is recovered and subjected to further processing. Typically, its components are separated.

More specifically, the method according to the present invention is mainly characterized by what is stated in the characterizing part of claim 1.

Considerable advantages are obtained by the present invention. Thus, the present invention offers a method for efficiently modifying the lignocellulosic material with greatly reduced formation of inhibiting compounds and without using a catalyst thereby lessening the problems related to current pre-treatment techniques. Also, the carbohydrates obtained with the method described in the present invention are more susceptible to enzymatic hydrolysis making the further processing of plant material more feasible than with known methods.

The present invention provides efficient conversion of any lignocellulosic material (wood, straw, bagasse, etc.) to hydrolysable form. The present invention also provides separation of lignin from lignocellulosic materials and dissolution of the lignin thus separated into the water phase.

Brief Description of the Drawings

Figure 1 shows in graphical form the comparison of enzymatic hydro lysability (10 FPU/g Celluclast 1.5L FP and 100 nkat/g of dry weight Novozym 188) of spruce oxidized with various alkali. Figure 2 shows in graphical form the enzymatic hydrolysability of solid fractions obtained from alkaline oxidation, catalytic oxidation and steam explosion pretreatments of spruce.

Figure 3 shows the effect of consistency in alkaline oxidation on enzymatic

hydrolysability, presented as % of dry weight of materials, of obtained pulp.

Detailed Description of Preferred Embodiments

As discussed above, the present invention is based on the finding that raw-material composed of a carbohydrate material, especially a lignocellulosic material is

decomposed/modified in alkaline water solutions under 0₂-containing atmosphere elevated temperature and optionally elevated pressure. In particular, the lignocellulosic material becomes more susceptible to enzymatic hydrolysis when treated as described here.

Methods with oxygen and alkali have been earlier used in the manufacture of pulp, but there is no suggestion in the art that these methods could be used as a pre-treatment in the manufacturing of other products than paper pulp. Pulp and paper processes are so called "fibrous applications", where a carbohydrate raw material is converted to products that are based on a fibrous (self-supporting) network. A typical example of a fibrous application is paper manufacturing. Such processes aim to retain carbohydrates, especially cellulose without deleterious degradation.

The method of this invention is suitable for production of material for use in non- fibrous applications and especially for production of solid fraction that can be efficiently converted to monosaccharides such as for example glucose, xylose and mannose for further processing, e.g. by fermentation.

The term "non-fibrous applications" is used for designating all other applications. One important non- fibrous application for (ligno)cellulosic biomass is being a starting material for second generation bio fuels, especially for ethanol, or other chemicals obtained by fermentation processes via sugar route.

The term "chemical" includes products of chemical industry, including biofuels, bulk and speciality chemicals, nanoparticles (including whiskers) and non- fibrous structural materials (e.g. lignin used as a component in board and panels). For clarity, "chemical" does not include fibrous products, such as cellulose pulps.

The raw-material can be derived from biomass, including e.g. wood, pulp, agricultural and industrial sidestreams, forestry residues and thinnings; agricultural residues, such as straw, bagasse, olive thinnings; energy crops, such as reed canary grass, willow, switchgrass, Miscanthus; peat; bagasse and sea biomass. Also municipal and industrial wastes can be used, particularly organic, solid or liquid wastes, and they can be selected from refuse derived fuel (RDF); wastes from sawmills, plywood, furniture and other mechanical forestry wastes; and waste slurries (including industrial and municipal wastes).

According to an embodiment of the invention, the raw-material is lignocellulosic material comprising cellulose, hemicellulose, lignin or combinations thereof. The raw-material can be present in fibrous state.

According to a preferred embodiment, the raw-materials of the present method include wood, pulp, recycled fibres, straw, agricultural, municipal and industrial wastes and similar compositions which contain carbohydrates. The method is particularly advantageous when the material is difficult to be handled with traditional pre-treatment processes. An example of such material is wood, especially softwood material.

The raw-material, usually a solid material containing some moisture, is typically reduced in size and slurried with aqueous medium. The slurry obtained preferably has a consistency of about 0.1 to 75 %, in particular about 0.5 to 30 % by weight (d.w./w), preferably 1 to 20 %, and most preferably ca. 4 to 20 % calculated from the weight of the water or aqueous solution or slurry. In the slurry, the lignocellulosic material is modified by degrading it at least partially in order to produce an aqueous slurry comprising solids and dissolved components. During processing a large portion of lignin and at least some carbohydrates are solubilised. At least a part (e.g. at least about 5 wt-%, preferably 20 to 100 wt-%) of the aqueous slurry is recovered, and at least a part (e.g. at least about 10 wt-%, preferably 20 to 100 wt-%) of the recovered slurry is used for non- fibrous applications.

The slurry or dispersion is alkaline, which in practice means that it contains an alkaline agent in the aqueous liquid phase. The pH of the slurry is initially at least 11 , preferably at least 11.5 and most preferably at least 11.8. Final pH, as the alkali is consumed during process, is less than 10, preferably less than 9.0 most preferably less than about 8.7 or 8.5. Thus, generally, the pH of the slurry after fractionation is 7 - 10, in particular 7 to 9, preferably about 7.4 to 8.8; for example about 8.5.

The reaction temperature is typically about 50 to 200 °C, preferably 80 to 150 °C, more preferably about 100 to 140 °C and most preferably about 120 °C.

The treatment is carried out in air or in oxygen gas or in air enriched with oxygen. Thus, in the following, the term "oxygen" is used to denote both. The pressure is typically ambient (normal) pressure or excess pressure up to about 50 bar (abs.); the partial pressure of oxygen is generally 1 to 50 bar (abs.), in particular 1 to 25 bar and preferably about 2 to 20 bar (absolute pressure). Treatment times may range from 0.1 to 48 hours, preferably from about 15 minutes to about 30 hours, most preferably from 1 to 24 hours, in particular from 4 to 20 h.

As is well known, reaction rate increases as temperature increases. Higher treatment temperature can be combined with shortened reaction time and vice versa. Therefore e.g. 5 h treatment at 140 °C can result in comparable result to that of 20 h at 120 °C.

The alkaline agent of the solution is selected from the group of alkali metal hydroxides and carbonates and bicarbonates and percarbonates, preferred alkaline agents are NaHC0₃, Na₂C0₃ and NaOH and mixtures thereof. Addition of NaOH allows effective regulation of the pH of the reaction suspension. On the other hand excellent results have surprisingly been obtained with the somewhat less alkaline sodium carbonate.

During the treatment, about 10 to 90 % by weight of the raw-material is dissolved and at least a part thereof is present in the aqueous phase of the aqueous suspension. Typically, material amounting to at least about 10 %, in particular about 15 to 85 %, for example 20 to 80 %, of the weight of the original raw-material is recovered in the soluble form in the aqueous slurry. Generally, the solubilization of the raw-material in the reaction mixture is 5 to 85, particularly 10 to 75, preferably 20 to 75, particularly preferably about 30 to 60, for example 40 to 50 % by weight. As will be discussed below, in a preferred embodiment, the solid fraction obtained represents preferably at a maximum 70 %, in particular 65 % or less of the weight of the original dry matter, which signifies a considerable dissolution of lignin and similar compounds along with, naturally, some of the carbohydrate material. The slurry obtained from the treatment contains solids and dissolved components; cellulose being present as a polymer, while most of the hemicellulose can be partly or fully hydro lyzed/degraded. Lignin is mostly dissolved, and in addition there are small-molecular degradation products (e.g. acids) in the solution. The lignin content of the insoluble fraction of the water slurry is decreased during the treatment. At the end of the treatment the lignin content is at the most 20 % (by weight) of the original content, in particular 15 % or less. The recovered material can be used for the production of glycans, including polysaccharides and chemicals derived therefrom, as well as for the production of various polyphenolic compounds, such as lignin and lignin derivatives, and compounds derived therefrom.

In particular, the fractions obtained are used for producing polysaccharides and the corresponding monosaccharides, disaccharides and oligosaccharides, alcoholic

compounds, lignin, chemicals and nanoparticles and nanowhiskers. The aqueous slurry can be fractionated into separate portions. Solid and liquid fractions can be separated by e.g. filtration and lignin can be recovered from liquid fraction by e.g. acid precipitation.

The recovered portion, i.e. either the solid matter, the liquid portion or a mixture of solids and liquid, is subjected to a further treatment step of mechanical treatments, chemical treatments, enzymatic treatments or combinations thereof. In particular the material is subjected to hydrolysis, fermentation and oxidation and combinations thereof optionally in further combination with preceding or subsequent mechanical treatments. The recovered material can also be subjected to a second treatment for increasing the yield or concentration of carbohydrates, chemicals, lignin, or nanoparticles or nano fibres. By extended hydrolysis of the polysaccharides and oligosaccharides, the yield of

monosaccharides is increased. The monosaccharides, such as xylose and glucose and galactose, are capable of being used for production of ethanol or other chemicals by fermentation.

Enzyme hydrolysis is one preferred option for extended hydrolysis. Preferably a mixture of enzymes containing cellulases and hemicellulases and optionally other enzymatic activities such as pectinases is used. Examples of suitable enzymes are cellulases e.g. EC 3.2.1.4, 3.2.1.21, 3.2.1.91, 3.2.1.132, xylanases e.g. EC 3.2.1.8, 3.2.1.32, 3.2.1.37, 3.2.1.72,

3.2.1.136, 3.2.1.156, other depolymerising glycosyl hydrolases e.g. EC3.2.1.25, 3.2.1.78, 3.2.1.89, 3.2.1.99, 3.2.1.100, 3.2.1.145, 3.2.1.15, polysaccharide debranching enzymes e.g. EC3.1.1.72, 3.1.1.73, 3.1.1.6, 3.2.1.131, 3.2.1.139, 3.2.1.55 or lignin modifying enzymes e.g. EC 1.10.3.2, 1.11.1.13. ,1.11.1.14 or so that they are suitable to be used in simultaneous saccharification and fermentation (SSF).

Surprisingly, the solid fraction obtained after the treatment can be very easily hydrolyzed. Thus, using a standard test (cf. Example 5 below) with a combination of a cellulase mixture and a β-glucosidase (incubation at pH 5, 45 °C for 24 hours), hydro lysability (i.e. degree of hydro lyzation) of at least 80 %, preferably at least 85 %, in particular at least 90 %, calculated from the maximum amount that can be obtained from a carbohydrate composition of the material (determined as described in Example 4). The hydro lysability can be quantified by determining the release of reducing sugars, for example as discussed in the article by Bernfeld (1955).

Various combinations of treatment and fermentation can be employed. One preferred embodiment comprises conversion of cellulosic/lignocellulosic material to ethanol involving separate hydrolysis and fermentation (SHF). Enzyme preparations can be tailored to be active in elevated temperatures for use immediately after or even during pre- hydrolysis. Conversion may also be simultaneous saccharification and fermentation (SSF) when enzymes should be active in temperature that is suitable for fermentative organism. The latter alternative can be carried out as simultaneous saccharification and hemicellulose fermentation (SSHF), which is also referred to as simultaneous saccharification and co- fermentation (SSCF). Short enzymatic prehydrolysis can be applied before simultaneous saccharification. The prehydrolysis denotes the period of time when enzymes hydro lyse the lignocellulosic substrate in the slurry before the inoculation of fermentative organism. After the prehydrolysis, fermentative organism is added and thereby starting the SSF. In addition, the treated material can also alternatively be further processed by micro organisms producing hydro lytic enzymes simultaneously to fermentation of sugars to ethanol or other products. This process called consolidated bioprocessing (CBP) can be applied either with no external enzymes, or with addition of some complementary or specific supplementary enzymes.

Generally, these embodiments can be applied to the production of any chemicals that can be prepared by fermentation from monosaccharides, such as ethanol, lactic acid, sugar acids, acetic acid and similar. For producing ethanol, the fermentation step is carried out in the presence of a fermenting micro-organism, capable of fermenting major lignocellulose-derived carbohydrates (sugars), such as hexoses and pentoses. Typically, the fermenting organism is capable of producing ethanol from the major lignocellulose derived sugars at temperature of 30 - 70 °C.

Examples of suitable organisms are the following, including genetically modified strains obtained from them: Yeasts: Saccharomyces cerevisiae, including genetically modified strains, Pichia stipitis, Candida shehatae, Hansenula polymorpha, Pachysolen tannophilus, Brettanomyces naardenensis, Pichia segobiensis, P.guillermondii, P. naganishii, Candida tenuis, C. albicans, C. tropicalis, C. maltosa, C. torresii, Metschnikowia bicuspidate, M. zobelii, Sporopachydermia quercuum, Wingea robertsii,

Bacteria: Zymomonas mobilis, Escherichia coli (genetically modified organisms (GMO) strain/strains), Klebsiella oxytoca (GMO strain), Clostridium thermocellum,

Thermoanaerobobacterium saccharolyticum. Fungi: Fusarium oxysporum, Candida millerii, C. tropicalis, C. parapsilosis, Petromyces albertensis, Debaromyces hansenii, Cellulomonas cellulans, Corynebacterium sp., Serratia marcescens.

According to another embodiment the suspension of solids and dissolved components obtained from treatment, is taken to a liquid separation step, from which a liquid phase containing dissolved polymers (lignin, sugar oligomers, pectins, etc.) and other dissolved molecules (degradation products) are obtained. These can be recovered as such and/or upgraded. Thus, at least a part (generally 10 - 100 % by weight) of the liquid portion can also be recovered and subjected to further treatment in order to precipitate at least some of the dissolved carbohydrate material or lignin. The solid phase remaining after liquid separation consists mostly of cellulose. This portion of the raw-material can be used for cellulose hydrolysis to yield sugar monomers or as a starting material for the recovery of nanoparticles and other nanostructures. According to one option, the solid phase is treated as explained above as a fermentation substrate.

Based on the above, the present invention also comprises a method in which a cellulosic or lignocellulosic raw material is processed with the objective of modifying it, or a part of it, into a material, which has non-fibrous applications, as well as applications based on the formed nanoparticles or nanostructures of the solid fraction. The method comprises the steps of

- subjecting the raw material to a treatment in the presence of Na₂CC"3 or alkaline agent being selected from alkali metal carbonates, hydroxides and percarbonates and an overpressure (i.e. an absolute pressure of more than 1 bar of) oxygen in order to form a modified material;

- separating the modified material into at least two fractions, a first solid fraction comprising cellulosic material depleted in lignin and a second liquid fraction containing dissolved lignin;

- recovering the modified material or at least a part of it;

- optionally subjecting the modified material, or some part of it, to further treatment in order to increase the content of a preselected component (up-grading of the material); and

- using the recovered material in an application.

Before the processing, one of more fractions can first be separated from the raw-material and excluded from further processing. It is also possible to bring the raw material into a more homogenised form for example by milling or crushing before it is being contacted with the alkaline agent, such as sodium carbonate, and oxygen.

The invention is illustrated by the following non-limiting examples. It should be understood, however, that the embodiments given in the description above and in the examples are for illustrative purposes only, and that various changes and modifications are possible within the scope of the invention. Examples

Example 1

In one embodiment of the invention Norway spruce saw dust (5 % d.w./w) is slurried in a solution of 26.5 g/L (0.25 mol/L) Na₂C0₃. The slurry is mechanically stirred under 10 arm 0₂ initial pressure and kept at 120 °C for 20 hours. The pH of the slurry was initially 11.8 but dropped to about 8.4 at the end of the reaction. The reaction is carried out in a 1 -litre stainless steel autoclave equipped with magnetic stirring and oil bath heating. In the reference treatment, spruce chips are treated similarly but oxygen is replaced by argon gas. The reaction in the presence of oxygen yields a slurry with a solid and solution fractions which are suitable for further processing according to examples below. Solid fraction yields are 74%, and 56% for argon reference and oxygen treatment, respectively.

The lignin content of solid fraction is determined gravimetrically from of air-dried, ground sample after heptane extraction by Klason lignin method by hydro lysing with 72 % sulphuric acid (Browning, 1967). Lignin content of solid fraction is decreased from 33 % to 31 % and 3.9 %, for reference treatment and oxygen treatment, respectively.

Example 2

In another embodiment of the invention spruce saw dust (5 % d.w./w) is slurried in a solution of 26.5 g/L Na₂C0₃. The slurry is mechanically stirred under 10 arm 0₂ initial pressure and kept at 140 °C for 5 hours. The pH of the slurry was initially 12.0 but dropped to about 8.5 at the end of the reaction. The reaction yields a slurry with a solid (yield 50 %) and solution fractions which are suitable for further processing according to examples below. The lignin content is analysed as described in example 1. The lignin content of solid fraction after oxidation at 140°C for 5 hours is 12 %.

Example 3 This example discloses ethanol production from alkaline oxidation pretreated softwood according to Example 1 by using simultaneous saccharification and fermentation (SSF).

Spruce saw dust (5.0 % d.w./w) is alkaline oxidation pretreated according to Example 1. Alkaline oxidised material was filtered and the solid fibrous fraction was washed with water. The simultaneous saccharification and fermentation was carried out by suspending the solid fraction to the separated filtrate to the 5.0 % (d.w./w) concentration, adjusting the pH to 5.0 and adding commercial enzyme preparations. The commercial enzyme preparations used were Celluclast 1.5 FG (cellulase mixture, 10 FPU/g d.w.) and Novozym 188 (β-glucosidase dosage 100 nkat/g d.w.). The yeast (strain VTT-B-08014) to the concentration of 1 g/1 (d.w.) was inoculated immediately after enzyme addition. It was suspended before inoculation with nutrients in 10 vol-% (of the hydro lysate) of YNB (Yeast Nitrogen Base). The hydrolysis and fermentation was carried out at 30 °C in waterlock flasks using slow agitation (100 rpm).

Simultaneous saccharification and fermentation (SSF) after alkaline pretreatment resulted in 48 hours an ethanol concentration of 15.6 g/1 and in 120 hours ethanol concentration of 16.8 g/1. Results show that ethanol production rate is fast and ethanol yield is good from the sugars released by enzymes on alkaline pretreated saw dust.

Example 4

This example discloses ethanol production from alkaline oxidation pretreated softwood according to Example 1 by using enzymatic prehydrolysis before simultaneous saccharification and fermentation (SSF).

Spruce saw dust (5.0 % d.w./w) is alkaline oxidation pretreated according to Example 1. Alkaline oxidised material was filtered and the solid fibrous fraction was washed with water. The simultaneous saccharification and fermentation was carried out by suspending the solid fraction to the separated filtrate to the 5.0 % (d.w./w) concentration, adjusting the pH to 5.0 and adding commercial enzyme preparations. The commercial enzyme preparations used were Celluclast 1.5 FG (cellulase mixture, 10 FPU/g d.w.) and Novozym 188 (β-glucosidase dosage 100 nkat/g d.w.). After 4 hours enzymatic prehydrolysis at 45°C the temperature was decreased to 30°C and the yeast (strain VTT-B-08014) was inoculated to the concentration of 1 g/1 (d.w.). It was suspended before inoculation with nutrients in 10 vol-% (of the hydrolysate) of YNB (Yeast Nitrogen Base). The hydrolysis and fermentation was carried out at 30 °C in waterlock flasks using slow agitation (100 rpm).

Simultaneous saccharification and fermentation (SSF) with 4 hours enzymatic

prehydrolysis after alkaline pretreatment resulted in 48 hours an ethanol concentration of 13.6 g/1 and in 120 hours ethanol concentration of 14.4 g/1. Results show that ethanol production rate is fast and ethanol yield is good from the sugars released by enzymes on alkaline pretreated saw dust.

Example 4

Spruce saw dust (5.0 % d.w./w) was pretreated by alkaline oxidation according to

Examples 1 and 2 in a solution of 26.5 g/L Na₂CC"3.

Alkaline oxidised material was filtered and the solid fibrous fraction was washed with water. The carbohydrate composition of washed solid fraction was analysed after acid hydrolysis to monosaccharides (Puis et al, 1985). 100 mg of solid fraction was hydrolysed by 1 ml of 72% sulphuric acid at 30 °C for 1 h. After addition of 28 ml water the material was autoclaved for 1 h at 120 °C and then analysed for sugar composition by HPLC (Tenkanen and Siika-aho, 2000). Results show that after alkaline oxidation a solid fraction having increased glucose content and thus high cellulose content was obtained (Table 1) whereas after reference treatment the carbohydrate composition was changed only slightly.

Table 1. Carbohydrate composition (% of dry weight) of alkaline oxidised washed fibres after acid hydrolysis by HPLC.

Alkaline

Reference treated Alkaline oxidation (Argon, 120 °C, oxidation (120 (140°C, 5 h)

Untreated spruce 20 h) (V3) °C, 20 h) V1 V2

Glucose 43% 54% 80% 77%

Xylose 5.7% 4.5% 3.6% 3.6%

Mannose 13.0% 5.2% 8.1 % 6.8%

Galactose 2.1 % 0.8% 0.3% 0.3%

Arabinose 1 .5% 0.9% 0.5% 0.5%

Rhamnose 0.1 % <0.1 % <0.1 % <0.1 %

Fructose <0.1 % <0.1 % 0.1 % 0.1 % Monosaccharides 65% 65% 93% 88% s polysaccharides 59% 59% 84% 79%

Example 5 Washed, solid fractions obtained by alkaline treatments were hydrolysed enzymatically to monosaccharides (from Example 4). Solid fraction was suspended into 50 mM sodium acetate buffer pH 5 into 10 mg/ml concentration. Enzymatic reaction was started by adding commercial cellulase mixture Celluclast 1.5L FP 10 FPU/g dry weight and commercial β- glucosidase Novozym 188 100 nkat/g dry weight. Suspensions were incubated at 45 °C with magnetic stirring for 24 hours. The carbohydrate composition of hydro lysates was analysed by HPLC after the hydrolysis reaction (cf. Example 4).

As a result, the carbohydrates in the washed fibre fractions of reference treated, oxidised at 120°C for 20h, and oxidised at 140 °C for 5h were hydrolysed enzymatically by 8%, 90% and 87%, respectively in 24 hours. Results show that alkaline treatment produced solid fraction with high enzymatic hydrolysability. Alkaline oxidation at 140°C for 5h resulted comparable enzymatic hydrolysability with oxidation at 120°C for 20h.

Example 6

The aim of this experiment was to compare the different alkaline solutions in the alkaline oxidation pretreatment and compare the enzymatic hydrolysability of solid fractions obtained. Calcium hydroxide, sodium hydroxide, potassium hydroxide, and sodium carbonate were applied in alkaline oxidation treatments. Treatment conditions and yields are presented in Table 2.

Table 2. Alkaline treatment conditions and yields of solid fractions (% of original dry wood).

KOH 0.25 120 10 20 13.5 7.8 60.5

Na₂C0₃ 0.25 120 10 20 11.7 8.6 55.9

* Including Ca(OH)₂-precipitate

Alkaline treated material was filtered and washed with water and dried at 100°C for 20 h. Ca(OH)₂-treated solid material contained much alkali after washing because of low solubility of Ca(OH)₂. After treatment, the carbohydrate composition of washed solid fraction was analysed after acid hydrolysis to monosaccharides by HPLC (Puis et al, 1985; Tenkanen and Siika-aho, 2000). (Table 3). Table 3. Carbohydrate composition (% of dry weight) of alkaline catalytically treated washed fibres after acid hydrolysis by HPLC.

Results in the Table 3 show that solid fractions of NaOH-, KOH- and Na₂C0₃- pretreatments had highest carbohydrate content, whereas solid material from Ca(OH)₂- treatments contained much precipitated alkali. The proportion of glucose of

monosaccharides was increased in the pretreatments with all alkaline solutions compared to original spruce saw dust (Table 1).

Solid fractions obtained by alkaline treatments were washed, dried at 100 °C for 20h, and ground (Retsch mill, blade 0.5), and hydrolysed enzymatically to monosaccharides. Solid fractions were suspended into 300 mM sodium acetate buffer pH 5 into 10 mg/ml concentration. Enzymatic reaction was started by adding Celluclast 1.5L FP 10 FPU/g and Novozym 188 in an amount 100 nkat/g dry weight. Suspensions were incubated at 45 °C with magnetic stirring for 48 hours. The release of reducing sugars was analysed during the hydrolysis reactions (Bernfeld, 1955). Figure 1 shows the enzymatic hydro lysability of solid fractions obtained from alkaline oxidation with calcium hydroxide, sodium hydroxide, potassium hydroxide, or sodium carbonate. As will appear, pretreatments with Na₂C0₃ resulted in highest enzymatic hydro lysability. KOH and NaOH were nearly as efficient chemicals in the pretreatment as Na₂C0₃, whereas all concentrations and temperatures of Ca(OH)₂-pretreatment resulted in the lowest enzymatic hydro lysability. The results obtained by reducing sugar assay were in some cases over 100% due to other reducing compounds reacting with the DNS-reagent. However, results obtained by reducing sugars-assay correlates well with the

monosaccharide content obtained by HPLC-assay (Table 4).

A hypothetical explanation for hydrolysis yields above 100 % (Table 4) is that enzymatic hydrolysis has with these materials with high hydrolysabilty given higher degree of hydrolysis than analytical acid hydrolysis (cf. Example 4). It is known that acid hydrolysis can result in lowered apparent sugar content either due to incomplete hydrolysis or degradation of released monosaccharides.

The results show the efficiency of Na₂C0₃ and NaOH in spruce pretreatment for enzymatic hydrolysis.

Table 4. Enzymatic hydrolysis of alkaline oxidised washed fibres at 45°C for 48h. Carbohydrates hydrolysed (% of sugars in solid fraction), analysed by HPLC.

Example 7

The aim of this experiment was to compare the enzymatic hydrolysability of alkaline oxidation treated material with catalytically oxidised and steam explosion treated spruce. Steam explosion is the state-of-the-art technology for pretreatment of lignocellulosic material for ethanol production.

Alkaline oxidation treatment was carried out according to Example 1. In catalytic oxidation that was performed for comparison, Norway spruce saw dust (5 % d.w./w) was suspended in a solution of 26.5 g/L (0.25 mol/L) Na₂C03. Catalysts were added to some of the examples (210 mg/L CuS0₄*5H₂0, 300 mg/L 1,10-phenanthroline) into solution before oxidation under 10 arm 0₂ initial pressure at 120 °C for 20 hours. Steam explosion pretreatment was carried out according to the method of Ohgren et al. (2006) by

impregnating with 2.5 % S0₂, and steam pretreating at 210 °C for 5 min.

Washed, solid fractions obtained by alkaline catalytic treatment or steam explosion were hydrolysed enzymatically to monosaccharides. Solid fractions were suspended into 50 mM sodium acetate buffer pH 5 into 10 mg/ml concentration. Enzymatic reaction was started by adding Celluclast 1,5L FP 10 FPU/g and Novozym 188 in an amount 100 nkat/g dry weight. Suspensions were incubated at 45 °C with magnetic stirring for 48 hours. The release of reducing sugars was analysed during the hydrolysis reactions (Bernfeld, 1955).

Figure 2 indicates the enzymatic hydro lysability of solid fractions obtained from alkaline oxidation , catalytic oxidation and steam explosion pretreatments. As apparent, alkaline treated spruce was hydrolysed by enzymes more efficiently than steam exploded spruce: both hydrolysis rate and hydrolysis level at the end of reaction was higher. Both alkaline oxidation and catalytic oxidation treatment produced material with high enzymatic hydro lysability. Catalysts in oxidation treatment did not give significantly sufficient improvement in the hydro lysability of wood.

Example 8

The aim of this experiment was to compare the different consistencies of the spruce saw dust in the slurry and compare the enzymatic hydro lysability of solid fractions obtained. In this experiment the ratio between the alkali concentration and the dry weight of the spruce saw dust was kept constant throughout the experiment set. The reactor was pressured to 10 bars of oxygen except in one reaction where the pressure was kept in 10 bars of oxygen through the experiment. Treatment conditions and yields are presented in Table 5. Table 5. Alkaline treatment conditions and yields of solid fractions (% of original dry wood).

* Pressure was kept constant. Highest dry weight yield 69 % was obtained in oxidation at 20 % consistency due to lowest solubilisation of lignin (Table 5). Although this is quite acceptable it is generally preferred with wood materials to have a yield of 65 % or less, indicating dissolution of 35 % of the original solid matter. Most of such dissolved matter is lignin. Alkaline oxidised material was filtered and the solid fibrous fraction was washed with water. Washed, solid fractions obtained by alkaline treatments were hydro lysed

enzymatically to monosaccharides . Solid fraction was suspended into 50 mM sodium acetate buffer pH 5 into 10 mg/ml concentration. Enzymatic reaction was started by adding commercial cellulase mixture Celluclast 1.5L FP 10 FPU/g dry weight and commercial β- glucosidase Novozym 188 100 nkat/g dry weight. Suspensions were incubated at 45 °C with magnetic stirring for 72 hours. The release of reducing sugars was analysed during the hydrolysis reactions (Bernfeld, 1955).

As a result, solid fractions from oxidisations at 10 and 15% consistency were hydro lysed to monosaccharides in 48 hours. Material oxidised at 20%> consistency was also hydrolysed, but with lower carbohydrate content of solid fraction, the hydrolysis level was lower.

Results show that alkaline oxidation at 10 - 20 % consistencies produced solid fraction with good enzymatic hydrolability. This can also be seen in Figure 3 which depicts the effect of consistency in alkaline oxidation on enzymatic hydrolysability of obtained pulp. References

Bernfeld, P. (1955) Amylases, a and b. In Colowick SP and Kaplan NO (eds) Methods of enzymology, Vol 1, Academic press, NY, pp 149-158.

Browning, B.L. 1967. Methods of wood chemistry. Vol. II. Interscience Publishers, New York. 882 p.

Puis, J., Poutanen, K., Korner, H.-U., and Viikari, L. (1985) Biotechnical utilization of wood carbohydrates after steaming pretreatment. Appl. Microbiol. Biotechnol. 22, 416- 423.

Tenkanen, M. and Siika-aho, M. (2000) An cc-glucuronidase of Schitzophyllum commune acting on polymeric xylan. J. Biotechnol, 78:2, 149-161.

Ohgren, K., Rudolf, A., Galbe, M., Zacchi, G. (2006) Fuel ethanol production from steam- pretreated corn stover using SSF at higher dry matter content. Biomass & Bioenergy 30, 863-869.

Claims

Claims:

1. A method of fractionating lignocellulosic biomass into at least one cellulose rich solid fraction and at least one liquid fraction, comprising the steps of

- adding an alkaline agent and water to the biomass to form a mixture having an alkaline pH, said alkaline agent being selected from alkali metal carbonates, hydroxides and percarbonates;

- contacting the biomass in the mixture with an oxidizing agent at an elevated

temperature; and

- continuing the contacting of the biomass with the oxidizing agent until most of the lignin is solubilised to produce a solid fraction comprising a cellulosic material having a reduced content of lignin and a liquid fraction comprising dissolved lignin.

2. The method according to claim 1, wherein the mixture is maintained at a temperature of 40 to 200 °C at a pressure of 1.1 to 30 bar (abs).

3. The method according to claim 1 or 2, wherein alkaline agent is added in an amount sufficient to increase the pH of the biomass to more than 11.5, preferably 12.0 or more, in particular to a value in the range of 12.5 to 14.

4. The method according to any of the preceding claims, wherein the mixture is contacted with an oxidizing agent selected from oxygen containing gases and oxygen. 5. The method according to any of the preceding claims, wherein the biomass is pretreated with the alkaline agent and the oxidizing agent in the mixture until the pH of the mixture is less than 9.0, preferably about 8.

5 or less.

6. The method according to any of the preceding claims, wherein at least a portion of the alkaline agent is selected from sodium carbonate, sodium percarbonate and sodium hydroxide or a mixture thereof.

7. The method according to any of claims 1 to 6, wherein the biomass is selected from wood, pulp, recycled fibres, straw, sugar cane bagasse, agricultural, municipal and industrial wastes and similar compositions which contain carbohydrates.

8. The method according to claim 7, wherein the biomass is wood-based, in particular the biomass is derived from or comprises softwood.

9. The method according to any of the preceding claims, comprising recovering a material and using it for production of glycans or polyphenol derived substances.

10. The method according to claim 9, wherein the material recovered comprises a solid fraction or a liquid fraction or a combination thereof.

11. The method according to claim 9 or 10, wherein the fractions are separated by e.g. filtration.

12. The method according to claim 11, wherein a recovered fraction, comprising solid matter, liquid or a mixture of solids and liquid, is subjected to a further treatment step selected from the group of mechanical treatments, chemical treatments and enzymatic treatments and combinations thereof.

13. The method according to claim 12, wherein the material is subjected to hydrolysis, fermentation, oxidation or a combination thereof, optionally in further combination with preceding or subsequent mechanical treatments.

14. The method according to any of claims 9 to 13, comprising producing, from at least one of the recovered fractions, carbohydrates selected from the group comprising polysaccharides and corresponding monosaccharides, disaccharides and oligosaccharides and nanoparticles and nanowhiskers.

15. The method according to any of claims 9 to 13, comprising producing, from at least one of the recovered fractions, alcoholic or fenolic compounds, including lignin and alcoholic chemicals are produced.

16. The method according to any of the preceding claims, wherein material recovered from a preceding step is subjected to a second treatment for increasing the yield or concentration of carbohydrates, chemicals, lignin, or nanoparticles or nanofibres.

17. The method according to claim 16, wherein the material is subjected to extended hydrolysis of the polysaccharides and oligosaccharides in order to increase the yield of monosaccharides.

18. The method according to claim 17, wherein there are produced monosaccharides, such as xylose and glucose and mannose and galactose, which are suitable for being used in the production of ethanol or other chemicals by fermentation.

19. The method according to any of the preceding claims, comprising recovering a solid fraction comprising a cellulosic material having a reduced content of lignin and exhibiting a hydrolysability of at least 80 %, preferably at least 85 %, in particular at least 90 %, calculated from the maximum amount that can be obtained from carbohydrate composition of the starting material, using a standard test carried out by incubating the starting material with a combination of a cellulase mixture and a β-glucosidase at pH5, 45 °C for 24 hours.

20. The method according to any of the preceding claims, wherein the solid fraction is further converted to monosaccharides for further processing.