Description
AU-PE*9
Xylanase for Improved Bleaching of
Paper Pulps
INTRODUCTION
Xylan is a major component of wood and non-wood
fibres. During cooking of pulps, the xylan is partially dissolved,
modified and re-precipitate onto the fibre surface. The application
of the enzyme, xylanase, to the cooked pulp removes some of the
re-precipitated xylan. This opens up the pulp matrix, allowing the
release of trapped soluble lignin. At the same time it allows
bleaching chemicals to penetrate more effectively. The overall
result is improved bleachability of the pulp with resulting
reduction in usage of bleaching chemicals.
AU-PE*9 Xylanase is an enzyme that degrades
xylan. AU-PE*9 is specific for xylan and
does not degrade cellulose. Xylanases produced by different
microorganisms operate optimally over a range of pH and
temperature. AU-PE*9 was developed from a proprietary strain of
bacterium for the paper pulp industry. AU-PE*9 is particularly
suited to the elevated temperatures and alkaline pH of kraft
pulps.
The
manufacturing process involves growing a specific proprietary
bacterium in bioreactors (fermenters), separating the cells from
the broth, and concentrating the clarified liquid. The product is
prepared as a concentrated liquid or light brown
powder.
TECHNOLOGICAL ADVANTAGE
AU-PE*9 acts as a pre-bleaching aid for paper
pulps. AU-PE*9 has specific advantages in
that it is stable and active at the alkaline pH and elevated
temperatures typical of kraft pulps.
The main driving factors for
acceptance of this technology in pulp mills have been the economic
and environmental advantages over chemical bleaching.
AU-PE*9 used as a pre-bleaching agent
for wood and non-woody pulps can reduce chemical bleach consumption
from between *5 to *0%.
PRODUCT DESCRIPTION
AU-PE*9 is a product derived from the culture of a strain of
Bacillus subtilis. The principal active ingredient of AU-PE*9 is
xylanase (endo*1,*-β-xylanase, EC 3.2.1.8), an enzyme that degrades
and solubilizes plant xylans.
AU-PE*9 is prepared with a xylanase activity of
about *5,**0 XU/mL. The xylanase units are determined on birchwood
soluble xylan at pH 6 and *0℃ over a *0 minute period. AU-PE*9
xylanase is effective over the pH range 6 to *0 and temperature
range *5 to *5℃
AU-PE*9 is a light yellow powder
with a density of 1.1 g/mL. It is readily miscible with
water.
BENEFITS OF
AU-PE*9
Reduce Organochlorines in
Wastewater：
For mills using active chlorine as a bleaching chemical, AU-PE*9
can eliminate or substantially reduce the chemical and
environmental load of toxic organochlorines in mill
effluent.
Reduce Chemical Costs：
For mills using environmentally friendly bleaching agents such as
hydrogen peroxide, AU-PE*9 can result in a significant cost
saving.
AU-PE*9 has the potential to reduce bleaching
chemical by*5 to *0%.
Increase Pulp Production
Capacity：
Pre-bleaching pulps with AU-PE*9 allows pulp production capacity to
be increased where on-site chlorine dioxide production is a
limiting factor.
Higher Pulp Brightness：
For a given dosage of bleaching chemical, pre-bleaching with
AU-PE*9 can give a higher brightness pulp, thus providing the mill
with a better quality paper.
AU-PE*9 can increase the pulp brightness by 2 to
6%.
Easily Incorporated：
AU-PE*9 is easily incorporated into existing bleach lines.
Typically, installation requires only a mixing tank and dosage
pump.
Reduce Effluent Load：
Application of AU-PE*9 in the bleach plant can reduce COD, BOD and
color of effluent.
AU-PE*9 can significantly reduce COD, BOD and
color of
effluent.
APPLICATION
AU-PE*9 xylanase can be added to pulp after
cooking or oxygen delignification and prior to bleaching for the
improvement of pulp bleachability. Almost every mill has unique
conditions of fibre furnish, pulping technology and bleach
sequence. The optimal dosage can also depend on the temperature, pH
and consistency of the pulp. Application protocols for AU-PE*9 can
be tailored to best suit the specific process. However, the
following general application optimal conditions
apply.
Dosage：
****0g/ T
pulp (o.d.basis)
Pulp properties：
pH between 6.5 and9.5
Temperature:
between *5 and *5℃
Pulp consistency: between 6 and *0% (recommended 8%)
Residence time： above 1 hour
STORAGE
AU-PE*9 maintains its stated activity for at least six months
when stored at temperatures below *5℃. The product maintains its
activity for considerably longer when stored at lower temperatures.
The product should not be frozen.
HANDLING PRECAUTIONS
AU-PE*9 is non-toxic and biodegradable. However, unnecessary
contact with the product should be avoided. Long term exposure to
protein based products such as AU-PE*9 may sensitise certain
individuals to the product
