Process for preparing and treating mechanical pulp with an enzyme preparation having cellobiohydralase and endo-.beta.-glucanase activity

A process for treating mechanical pulp having a cellobiohydrolase activity effective for modifying crystalline parts of the cellulose, an endo-.beta.-glucanase less than that which will significantly hydrolyze the cellulose, and a mannanase activity; and wherein the endo-.beta.-glucanase activity is low compared to the cellobiohydrolase activity.

The present invention relates to a process in accordance with the preamble 
of claim 1 for preparing mechanical pulp. 
According to a process of this kind, the wood raw material is disintegrated 
into chips, which then are defibered to the desired freeness value. During 
the production process, the raw material is subjected to an enzymatic 
treatment. 
The invention also relates to an enzyme preparation according to the 
preamble of claim 16, suitable for the treatment of mechanical pulp. 
The chemical and mechanical pulps possess different chemical and fibre 
technical properties and thus their use in different paper grades can be 
chosen according to these properties. Many paper grades contain both types 
of pulps in different proportions according to the desired properties of 
the final paper products. Mechanical pulp is often used to improve or to 
increase the stiffness, bulkyness or optical properties of the product. 
In paper manufacture the raw material have first to be defibered. 
Mechanical pulp is mainly manufactured by the grinding and refining 
methods, in which the raw material is subjected to periodical pressure 
impulses. Due to the friction heat, the structure of the wood is softened 
and its structure loosened, leading finally to separation of the fibres 
(1). 
However, only a small part of the energy spent in the process is used to 
separate the fibres: the major part being transformed to heat. Therefore, 
the total energy economy of these processes is very poor. 
Several methods for improving the energy economy of mechanical pulping are 
suggested in the prior art. Some of these are based on pretreatment of 
chips by, e.g., water or acid (FI Patent Specifications Nos. 74493 and 
87371). Also known are methods which comprise treating the raw material 
with enzymes to reduce the consumption of the refining energy. Thus. 
Finnish Patent Application No. 895676 describes an experiment in which 
once-refined pulp was treated with a xylanase enzyme preparation. It is 
stated in the application that this enzyme treatment would, to some 
extent, decrease the energy consumption. In said prior art publication the 
possibility of using cellulases is also mentioned, but no examples of 
these are given nor are their effects shown. As far as isolated, specified 
enzymes are concerned, in addition to hemicellulases, the interest has 
been focused on lignin modifying enzymes, such as laccase (5). A treatment 
using the laccase enzyme did not, however, lead to decreased energy 
consumption (5). 
In addition to the afore-mentioned isolated enzymes, the application of 
growing white rot fungi in the manufacture of mechanical pulps has also 
been studied. Carried our before defiberization, such a treatment with a 
white rot fungus has been found to decrease the energy consumption and to 
improve the strength properties of these pulps (6,7,8). The drawbacks of 
these treatments are, however, the long treatment time needed (mostly 
weeks), the decreased yield (85 to 95%), the difficulty to control the 
process and the impaired optical properties. 
The aim of this method of invention is to remove the drawbacks of the known 
techniques and to provide a completely new method for the production of 
mechanical pulp. 
It is known that the amount and temperature of water bound to wood are of 
great importance for the energy consumption and quality of the pulp (1). 
The water bound to wood is known to decrease the softening temperature of 
hemicelluloses and lignin between the fibres and simultaneously to weaken 
the interfibre bonding, which improves the separation of fibres from each 
others (2). During refining the energy is absorbed (bound) mainly by the 
amorphous parts of the fibre material, i.e. the hemicellulose and lignin. 
Therefore, an increase of the portion of amorphous material in the raw 
material improves the energy economy of the refining processes. 
The invention is based on the concept of increasing the amorphousness of 
the raw material during mechanical pulping by treating the raw material 
with a suitable enzyme preparation, which reacts with the crystalline, 
insoluble cellulose. By treating the raw material also with another 
enzyme, which improves the action of that enzyme active on crystalline 
cellulose, the efficiency of the treatment can further be enhanced. 
The enzymes responsible for the modification and degradation of cellulose 
are generally called "cellulases". These enzymes are comprised of 
endo-.beta.-glucanases, cello-biohydrolases and .beta.-glucosidase. In 
simple terms, even mixtures of these enzymes are often referred to as 
"cellulase", using the singular form. Very many organisms, such as wood 
rotting fungi, mold and bacteria are able to produce some or all of these 
enzymes. Depending on the type of organism and cultivation conditions, 
these enzymes are produced usually extracellularly in different ratios and 
amounts. 
It is generally well known that cellulases, especially cellobiohydrolases 
and endoglucanases act strongly synergistically, i.e. the concerted, 
simultaneous effect of these enzymes is more efficient than the sum of the 
effects of the individual enzymes used alone. Such concerted action of 
enzymes, the synergism, is however, usually not desirable in the 
industrial applications of cellulases on cellulosic fibres. Therefore, it 
is often desired to exclude the cellulase enzymes totally or at least to 
decrease their amount. In some applications very low amounts of cellulases 
are used for e.g. the removal of the fines, but in these applications the 
most soluble compounds are hydrolyzed to sugars in a limited hydrolysis as 
a result of the combined action of the enzymes (3,4). 
In our experiments we have been able to show that a synergistically acting 
cellulase enzyme product, i.e. the "cellulase" cannot be used to improve 
the manufacture of mechanical pulps because the application of this kind 
of enzyme product leads to the hydrolysis of insoluble cellulose and thus 
impairs the strength properties of the fibres. In connection with the 
present invention, however, it has surprisingly been found that by using a 
cellulase enzyme preparation, which does not posses a synergistic mode of 
action, cellulose can be modified in an advantageous way and desired 
modifications can be achieved without remarkable hydrolysis or yield 
losses. According to the method of invention a cellulase preparation, 
having an essential cellobiohydrolase activity and--as compared with the 
cellobiohydrolase activity--a low endo-.beta.-glucanase activity, if any, 
is used. 
Suprisingly we have found out that the action of the cellobiohydrolase can 
specifically be improved by the addition of a mannanase. 
The cellulase enzymes are composed of functionally two different domains: 
the core and the cellulose binding domain (CBD), in addition to the linker 
region combining these two domains. The active site of the enzyme is 
situated in the core. The function of the CBD is thought to be mainly 
responsible for the binding of the enzyme to the insoluble substrate. If 
the tail is removed, the affinity and the activity of the enzyme towards 
high molecular weight and crystalline substrates is essentially decreased. 
According to the process of the invention, the raw material to be refined 
is treated with an enzyme, able specifically to decrease the crystallinity 
of cellulose. This enzyme can be e.g. cellobiohydrolase or a functional 
part of this enzyme and, as a cellulase enzyme preparation, it acts 
non-synergistically, as described above. In this context, "functional 
parts" designate primarily the core or the tail of the enzyme. Also 
mixtures of the above mentioned enzymes, obtainable by e.g. digestion 
(i.e. hydrolysis) of the native enzymes can be used. 
Within the scope of the present application, the term "enzyme preparation" 
is used for designating any product containing at least one 
cellobiohydrolase enzyme and at least one mannanase enzyme or structural 
parts of these. Thus, an enzyme preparation can, for instance, comprise a 
growth medium containing said enzymes or a mixture of two or several 
separately produced enzymes. 
For the purpose of the present application, the term "cellobiohydrolase 
activity" denotes an enzyme preparation, which is capable of modifying the 
crystalline parts of cellulose. 
Thus, the term "cellobiohydrolase activity" includes particularly those 
enzymes, which produce cellobiose from insoluble cellulose substrates. 
This term covers, however, also all enzymes, which do not have a clearly 
hydrolyzing effect or which only partially have this effect but which, in 
spite of this, modify the crystalline structure of cellulose in such a way 
that the ratio of the crystalline and amorphous parts of the 
lignocellulosic material is diminished, i.e. the part of amorphous 
cellulose is increased. These last-mentioned enzymes are exemplified by 
the functional parts of e.g. cellobiohydrolase together or alone. 
"Mannanase" or "mannanase-activity", respectively, refers to an enzyme, 
which is capable of cleaving polyose chains containing mannose units 
(mannopolymers), such as glucomannan, galactoglucomannan and 
galactomannan. Endo-1,4-.beta.-mannanase can be mentioned as an example of 
mannanases. 
According to the invention the treatments with a cellobiohydrolase and a 
mannanase are performed simultanously or sequentially. In the latter case 
it is preferred to perform the mannanase treatment or the treatment with a 
cellobiohydrolase immediately one after the other without any washing step 
between in order to utilize the synergistic effect of the combined use. 
According to a particularly preferred embodiment of the invention, the 
enzymatic treatments are performed by mixing the pulp with an enzymatic 
preparation, which contains both cellobiohydrolase activity and mannanase 
activity. This type of enzyme preparation can be obtained by mixing two 
enzyme preparations: one containing cellobiohydrolase activity and the 
other one containing mannanase activity. According to the invention the 
enzyme preparation can also be a growth filtrate, where a strain of a 
microorganism producing cellobiohydrolase and mannanase has been grown. 
This type of a strain is exemplified by genetically modified 
microorganisms, to which the genes coding for cellobiohydrolase and 
mannanase have been transferred and which does not produce unwanted or 
detrimental enzymes. 
According to the process of the present invention, the enzyme treatment is 
preferably carried out on the "coarse pulp" of a mechanical refining 
process. This term refers in this application to a lignocellulosic 
material, used as raw material of the mechanical pulp and which already 
has been subjected to some kind of fiberizing operation during mechanical 
pulping e.g. by refining or grinding. Typically, the drainability of the 
material to be enzymatically treated, is about 30 to 1,000 ml. preferably 
about 300 to 700 ml. When applied directly to the chips, the enzyme 
treatment is usually not as efficient, because it is difficult to achieve 
an efficient diffusion (adsorption) of the enzyme preparation into the 
fibres of the raw material, if still in the form of chips. In contrast, 
e.g. a pulp, once refined, is well suited for use in the method of 
invention. The term coarse pulp thus encompasses, e.g., once refined or 
ground pulp, the rejects and long fibre fractions, and combinations of 
these, which have been produced by thermomechanical pulping (e.g. TMP) or 
by grinding (e.g. GW and PGW). It is essential for the invention that the 
enzyme treatment be carried out at least before the final refining stage. 
The process is not limited to a certain wood raw material, but it can be 
applied generally to both soft and hard wood species, such as species of 
the order of Pinacae (e.g. the families of Picea and Pinus), Salicaceae 
(e.g. the family of Populus) and the species in the family of Betula. 
According to a preferred embodiment of the invention refined (e.g. 
once-refined) mechanical pulps, having drainabilities in the range of 50 
to 1,000 ml, are treated with an enzyme preparation which contains 
cellobiohydrolase and mannanase enzymes at 30.degree. to 90.degree. C., in 
particular at 40.degree. to 60.degree. C., at a consistency of 0.1 to 20%, 
preferably 1 to 10%. The treatment time is 1 min to 20 h, preferably about 
10 min to 10 h. in particular about 30 min to 5 h. The pH of the treatment 
is held neutral or slightly acid or alkaline, a typical pH being 3 to 10, 
preferably about 4 to 8. The enzyme dosage varies according to the type of 
pulp and the cellobiohydrolase activity of the preparation, but is 
typically about 1 .mu.g to 100 mg of protein per gram of od. pulp. 
Preferably, the enzyme dosage is about 10 .mu.g to 10 mg, in particular 50 
.mu.g-10 mg of protein per gram of pulp. 
The process according to the present invention can be combined with 
treatments carried out with other enzymes, such as hemicellulases (e.g. 
xylanases, glucuronidases and mannanases) or esterases. In addition to 
these enzymes, additional enzyme preparations containing 
.beta.-glucosidase activity can be used in the present process, because 
this kind of .beta.-glucosidase activity prevents the end product 
inhibition and increases the efficiency of the method. 
Cellobiohydrolase enzyme preparations are produced by growing suitable 
micro-organism strains, known to produce cellulase. The production strains 
can be bacteria, fungi or mold. As examples, the micro-organisms belonging 
to the following species can be mentioned: 
Trichoderma (e.g. T. reesei), Aspergillus (e.g. A. niger), Fusarium, 
Phanerochaete (e.g. P. chrysosporium; 12!), Penicillium (e.g. P. 
janthinellum, P. digitatum), Streptomyces (e.g. S. olivochromogenes, S. 
flavogriseus), Humicola (e.g. H. insolens), Cellulomonas (e.g. C. fimi) 
and Bacillus (e.g. B. subtilis, B. circulans, 13!). Also other fungi can 
be used, strains belonging to species, such as Phlebia, Ceriporiopsis and 
Trametes. 
It is also possible to produce cellobiohydrolases or their functional parts 
with strains, which have been genetically improved to produce specifically 
these proteins or by other genetically modified production strains, to 
which genes, coding these proteins, have been transferred. When the genes 
coding the desired protein(s) (14) have been cloned it is possible to 
produce the protein or its part in the desired host organism. The desired 
host may be the fungus T. reesei (16), a yeast (15) or some other fungus 
or mold, from species such as Aspergillus (18), a bacterium or any other 
micro-organism, whose genetic is sufficiently known. 
According to a preferred embodiment the desired cellobiohydrolase is 
produced by the fungus Trichoderma reesei. This strain is a generally used 
production organism and its cellulases are fairly well known. T. reesei 
synthesizes two cellobiohydrolases, which are later referred to as CBH I 
and CBH II, several endoglucanases and at least two .beta.-glucosidases 
(17). The biochemical properties of these enzymes have been extensively 
described on pure cellulosic substrates. Endoglucanases are typically 
active on soluble and amorphous substrates (CMC, HEC, .beta.-glucan). 
whereas the cellobiohydrolases are able to hydrolyze only crystalline 
cellulose. The cellobiohydrolases act clearly synergistically on 
crystalline substrates, but their hydrolysis mechanisms are supposed to be 
different from each other. The present knowledge on the hydrolysis 
mechanism of cellulases is based on results obtained on pure cellulose 
substrates, and may not be valid in cases, where the substrate contains 
also other components, such as lignin or hemicellulose. 
The cellulases of T. reesei (cellobiohydrolases and endoglucanases) do not 
essentially differ from each other with respect to their optimal external 
conditions, such as pH or temperature. Instead they differ from each other 
with respect to their ability to hydrolyze and modify cellulose in the 
wood raw material. 
As far as their enzymatic activities are concerned, the cellobiohydrolases 
I and II differ also to some extent from each other. These properties can 
be exploited in the present invention. Therefore, it is particularly 
preferable to use cellobiohydrolase I (CBH I) produced by T. reesei 
according to the present invention for reducing the specific energy 
consumption of mechanical pulps. The pI value of this enzyme is, according 
to data presented in the literature, 3.2 to 4.2 depending on the form of 
the isoenzyme (19) or 4.0 to 4.4, when determined according to the method 
presented in Example 2. The molecular weight is about 64,000 when 
determined by SDS-PAGE. It must be observed, however, that there is always 
an inaccuracy of about 10% in the SDS-PAGE method. Cellobiohydrolases 
alone or combined to e.g. hemicellulases can be particularly preferably 
used for the modification of the properties of mechanical pulps, e.g. for 
improving the technical properties of the paper (i.e. the handsheet 
properties) prepared from these pulps. Naturally, also mixtures of 
cellobiohydrolases can be used for the treatment of pulps. 
The mannanase used in the present process can be produced by fungi or 
bacteria, such as microorganisms belonging to the following genera: 
Trichoderma (e.g. T. reesei), Aspergillus (e.g. A. niger), Phanerochaete 
(e.g. P. chrysosporium), Penicillium (e.g. P. janthinelium, P. digitatum) 
and Bacillus. As a host organism for mannanase production a white-rot 
fungi belonging to the following genera such as Phlebia, Ceriporiopsis and 
Trametes can be used. 
The two main Trichoderma reesei mannanases, which have pI-values of 4.6 and 
5.4 and molecular weights of 51 kDa and 53 kDa, respectively, can be 
mentioned as examples of suitable mannanases. 
It is also possible to produce mannanases by strains, which have been 
improved to produce the proteins in question, or by other genetically 
improved host organisms, where the genes coding for these proteins have 
been transferred. When the genes coding for the desired protein(s) have 
been cloned 15!, it is possible to produce the protein in a desired host 
organism. The desired host may be the fungus T. reesei, a yeast, an other 
fungus or mold from genera such as Aspergillus, a bacterium or any other 
microorganism, whose genetic is suffiently known. 
Even the production of mannanase by the original host organism (e.g. 
Trichoderma) can be improved or modified after gene isolation by known 
gene means, by, for instance, transferring several copies of the 
chromosomal mannanase gene into the fungus under the (e.g. stronger) 
promoter of another gene and thus to provide mannanase expression under 
desired growth conditions, such as on the culture media which natively do 
not produce mannanase. 
According to one preferred embodiment the desired mannanases can be 
produced by Trichoderma reesei. This strain is a generally used production 
organism and its hemicellulases are fairly well known. T. reesei 
synthetizes at least five mannanases. 
According to the present invention cellobiohydrolases and mannanases are 
isolated from the rest of proteins in the culture filtrate by a fast 
separation method based on an anionic ion exchanger. The method is 
described in detail in Examples 1 and 3. The invention is not, however, 
restricted to this enzyme isolation method, but it is possible to isolate 
or enrich the enzyme with other known methods. If the production strain 
does not produce harmful enzymes, the culture filtrate can be separated 
and enriched using well known methods. 
Significant advantages can be obtained with this invention. Thus, with this 
method the specific energy consumption can be remarkably decreased; as the 
examples described below show in addition to a lower energy consumption 
also better optical properties of the pulp can be achieved using the 
method of invention, as compared with untreated raw materials. According 
to the method of invention, in which the synergistic action of cellulases 
is absent or only insignificant, also the problems involved in the above 
mentioned fungal treatments can be avoided. Thus, the treatment time lasts 
only for few hours, the yield is extremely high, the quality of the pulp 
is good and the connection of the method to the present processes is 
simple. 
The method can be applied in all mechanical or semimechanical pulping 
methods, such as in the manufacture of ground wood (GW, PGW), 
thermomechanical pulps (TMP) and chemimechanical pulps (CTMP). 
In the following, the invention is described in more detail with the help 
of the following non-limiting examples.

EXAMPLE 1 
Purification of cellobiohydrolase I 
The fungus Trichoderma reesei (strain VTT-D-86271, RUT C-30) was grown in a 
2 m.sup.3 fermenter on a media containing 3% (w/w) Solka floc cellulose, 
3% corn steep liquor. 1.5% KH2PO4 and 0.5% (NH.sub.4).sub.2 SO.sub.4. The 
temperature was 29.degree. C. and the pH was controlled between 3.3 and 
5.3. The culture time was 5 d. whereafter the fungal mycelium was 
separated by a drum filter and the culture filtrate was treated with 
bentonite, as described by Zurbriggen et al. (10). After this the liquor 
was concentrated by ultrafiltration. 
The isolation of the enzyme was started by buffering the concentrate by gel 
filtration to pH 7.2 (Sephadex G-25 coarse). The enzyme solution was 
applied at this pH (7.2) to an anion exchange chromatography column 
(DEAE-Sepharose FF), to which most of the proteins in the sample, 
including CBH I, were bound. Most of the proteins bound to the column 
including also other cellulases than CBH I were eluated with a buffer (pH 
7.2) to which sodium chloride was added to form a gradient in the eluent 
buffer from 0 to 0.12M. The column was washed with a buffer at pH 7.2, 
containing 0.12M NaCl, until no significant amount of protein was eluted. 
CBH I was eluted by increasing the concentration of NaCl to 0.15M. The 
purified CBH I was collected from fractions eluted by this buffer. 
EXAMPLE 2 
Characterization of CBH I 
The protein properties of the enzyme preparation purified according to 
example 1 were determined according to usual methods of protein chemistry. 
The isoelectric focusing was run using a Pharmacia Multiphor II System 
apparatus according to the manufacturer's instructions using a 5% 
polyacrylamide gel. The pH gradient was achieved by using a carrier 
ampholyte Ampholine, pH 3.5-10 (Pharmacia), where a pH gradient between 
3.5 and 10 in the isoelectric focusing was formed. A conventional gel 
electrophoresis under denaturating conditions (SDS-PAGE) was carried out 
according to Laemmli (11), using a 10% polyacrylamide gel. In both gels 
the proteins were stained with silver staining (Bio Rad. Silver Stain 
Kit). 
For CBH I the molecular weight obtained was 64 000 and the isoelectric 
point 4.0-4.4. As judged from the gels, over 90% of the proteins consisted 
of CBH I. 
EXAMPLE 3 
Isolation of mannanase 
In order to isolate the enzyme, the culture medium of Trichoderma reesei 
(Rut C-30. VTT D-86271) was first treated with bentonite, as described by 
Zurbriggen et al. (1990). Then the solution was concentrated by 
ultrafiltration and the concentrate was dried by spray drying. 
The isolation of the enzyme was started by dissolving the spray dried 
culture medium in a phosphate buffer. The insoluble material was separated 
by centrifugation and the enzyme solution was buffered by gel filtration 
to pH 7.2 (Sephadex G-25). The enzyme solution was pumped at this pH 
through a cation exchange chromatography column (CM-Sepharose FF), to 
which a part of the proteins of the sample were bound. The desired enzyme 
was collected in the fractions eluted through the column. 
At said pH (pH 7.2) the enzyme solution was pumped to an anion exchange 
chromatography column (DEAE-Sepharose FF), to which most of the proteins 
of the sample were bound. The desired enzyme was collected in the fraction 
eluted through the column. 
The enzyme-containing fractions were further purified by using hydrophobic 
interaction chromatography (Phenyl Sepharose FF). The enzyme was bound to 
said material at a salt concentration of 0.3M (NH.sub.4).sub.2 SO.sub.4. 
The bound enzyme was eluted with a buffer at pH 6.5, so as to form a 
decreasing linear concentration gradient of (NH.sub.4).sub.2 SO.sub.4 from 
0.3 to 0M. After this, elution was continued with the buffer of pH 6.5. 
The mannanase enzyme was collected at the end of the gradient and in the 
fractions collected after that. 
The enzyme solution was buffered by gel filtration to pH 4.3 (Sephadex 
G-25). The enzyme was bound at this pH to a cation exchange chromatography 
column (CM-Sepharose FF), and a part of the proteins bound to the column 
(i.a. most of the remaining cellulases) were eluted with a buffer, pH 4.4. 
The mannanase enzyme was eluted with a buffer, pH 4.3, to which sodium 
chloride was added in order to form a linear cocentration gradient of 
sodium chloride from 0 to 0.05M. The purified enzyme was collected in the 
fractions eluted by the gradient. 
EXAMPLE 4 
Characterization of mannanase 
The protein properties of the enzyme preparation purified according to 
Example 3 were determined by methods known per se in the protein 
chemistry. The molecular weights were determined by the SDS-PAGE -method. 
The preparation contains two mannanase isoenzymes (20), which biochemically 
and functionally proved to be almost identical. The pIs of the enzymes are 
4.6 and 5.4, respectively. The molecular weights are 51 kDa and 53 kDa, 
respectively. The optimum pH of both isoenzymes is 3-3.5 and optimum 
temperature for activity testing is 70.degree. C. 
EXAMPLE 5 
Hydrolytic action of cellobiohydrolase and mannanase 
Middle coarse fibers (mesh+100) fractioned from spruce TMP pulp were 
treated with CBH I and mannanase enzymes at 48.degree. C. for 48 hours. 
The fractioned pulp was mixed in distilled water to obtain a consistency 
of 2% and the pH was set to 4.5 with sulphuric acid. In the experiment the 
enzyme dosages were as folllows: CBH I 2 mg/g and mannanase 0.1 mg/g. In 
the experiments above mentioned enzyme dosages were added to pulp samples 
separately or simultaneously. Amounts of reducing sugars, cellobiose (main 
hydrolytic product of CBH I) and mannose solubilized by the enzymes were 
analyzed and are shown in Table 1. 
TABLE 1 
______________________________________ 
Carbohydrates released by CBH I and mannanase from spruce TMP pulp 
(treatment time 48 hours, enzyme dosages: CBH I 2 mg/g and mannanase 
0.1 mg/g) 
Conc. of cellobiose and 
Reducing sugars, 
mannose, g/l 
Treatment % d.w. Cellobiose 
Mannose 
______________________________________ 
CBH I 0.61 0.12 &lt;0.01 
Mannanase 0.50 &lt;0.01 0.01 
CBH I + mannanase 
1.68 0.21 0.03 
______________________________________ 
A clear synergistic effect of the enzymes in the partial hydrolysis of 
spruce TMP pulp can clearly be recognized, when acting simultanously both 
enzymes solubilized more reducing sugars as well as cellobiose and mannose 
as compared to a situation where both enzymes acted alone. 
EXAMPLE 6 
The effects of the enzymatic treatment (CBH I+mannanase) on the specific 
energy consumption of mechanical pulping and on the optical properties of 
the pulps 
Spruce TMP pulp samples (CSF 640 ml) were treated with enzyme preparations, 
which contained CBH I alone and a mixture of CBH I and mannanase. The 
consistency of the pulp was 5% in tap water, treatment time 2 hours and 
temperature 45.degree.-50.degree. C. pH of the pulp was adjusted to 4.5 
with sulphuric acid. In each experiment 1 kg (o.d.) of pulp was treated 
using enzyme dosages shown below: 
1) CBH I 0.2 mg/g 
2) CBH I 0.1 mg/g+mannanase 0.1 mg/g 
After the treatments the pulps were dewatered and homogenized. The 
procedure for a control sample was otherwise the same but without an 
addition of an enzyme. 
The pulps were refined with a Sprout-Waldron single rotating disk refiner 
using decreasing plate settings. The pulps were refined three times to 
obtain CSF values about 150-160 ml. Energy consumption of refining was 
measured in each case. From the refined pulps handsheets were also made 
and tested according to the SCAN-methods. Results are shown in Table 2. 
TABLE 2 
______________________________________ 
Specific energy consumption (at CSF level of 120 ml) and optical 
properties of the handsheets. 
Light Light 
ISO- scat- absorp- 
Spec. energy 
bright- tering 
tion 
consumption, 
ness, coeff. 
coeff. 
Opacity 
Treatment 
kWH/kg % m.sup.2 /kg 
m.sup.2 /kg 
% 
______________________________________ 
Control 2.25 58.0 50.1 2.87 92.3 
CBH I 2.15 58.2 50.2 2.73 91.0 
CBH I + man 
2.0 59.8 52.5 2.46 91.0 
______________________________________ 
According to the results it can be concluded that the treatment with CBH 
I+mannanase gives a lower energy consumption and improves ISO-brightness 
and light scattering as compared to the untreated control or to the CBH I 
treated sample. 
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