synergistic effect of ultrafiltered xylano-pectinolytic enzymes produced simultaneously
by a bacterial isolate was evaluated in prebleaching of hardwood kraft pulp.
Absorption spectrum of ultrafiltered enzymes preparation showed the removal of
many impurities. The Vmax/Km ratio of ultrafiltered enzymes was sufficiently high,
indicating higher affinity of these enzymes for their substrates and hence
appears to have more catalytic efficiency. Reduction in kappa number and
yellowness after ultrafiltered and crude enzymatic treatment of pulp was
11.36%, 1.94% and 8.69%, 1.71% respectively. Increase in brightness of
handsheets after treatment with ultrafiltered and crude enzymes was 7.63% and
6.76% respectively. Gain in other physical properties viz. burst factor
(1.03%), tear factor (0.98%), breaking length (1.4%), gurley porosity (1.5%),
viscosity (1.55%) and double fold number (2.7%) was also observed in ultrafiltered
enzymes treated handsheets. The pretreatment of pulp with these enzymes
resulted in 28% reduction of chlorine consumption in bleaching stage. So, the ultrafiltered
enzymes enhanced the bleaching power by showing more reduction in kappa number
and chlorine consumption with better optical properties and strength of paper
in comparison to crude enzymes. This is the first report mentioning the
suitability of this pollution reducing technology in generating good quality
paper from hardwood kraft pulp.

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Biobleaching; Brightness; Crude and ultrafiltered
enzymes; Kappa number; Kraft pulp; Xylano-pectinolytic enzymes


paper manufacturing industries are the main contributors of environmental
pollution. During bleaching process, chlorine/chlorine dioxide and alkali- hydrogen
peroxide are used for the removal of lignin from kraft pulp. These industries
are producing very toxic effluents which are harmful for the biological systems
(Bajpai et al. 2006) and also make the waste water treatment expensive (Zhang
et al.2008). Looking at the load on the environment, these industries have to
modify their processes for their survival. Biobleaching using enzymes can lower
the consumption of toxic chemicals. Also enzymes have ability to create good
strength paper but high production cost of bleaching enzymes have restricted
their use in many paper industries. Now there is heavy pressure on paper and
pulp industries to switch over to enzymatic bleaching in order to reduce the
pollution created by these industries.

is need to develop technologies which could reduce the pollution and
simultaneously enhance the quality of the product. Crude xylano-pectinolytic
enzymes, produced concurrently by a cellulase free bacterial isolate using
cost-effective media, have been used in the bleaching of mixed hardwood and
bamboo kraft pulp (Kaur et al. 2010) and plywood
industrial waste soda anthraquinone pulp (Agrawal et al. 2016). The
combination of enzymes produced by a bacterial isolate makes the bleaching
process cost-effective and also reduces the consumption of bleaching chemicals,
ultimately responsible for reduction in pollution and also lowers the waste
water treatment cost. The less consumption of chemicals also results in the production
of high strength paper.

In this paper, ultrafiltration
of the simultaneously produced xylano-pectinolytic enzymes preparation was done
and ultrafiltered xylano-pectinolytic enzymes preparations were used for the
bleaching purpose. This is the first report showing the enhanced capability of ultrafiltered
xylano-pectinolytic enzymes in bleaching of hardwood kraft pulp, resulting in
higher reduction in the consumption of toxic chemicals being used
conventionally for bleaching as well as in producing superior quality paper in
comparison to crude enzymes.

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