both soluble starch and raw corn starch to produce glucose and maltose [94].
The thermophilic and alkaliphilic Bacillus sp. strain XAL601 was reported to
produce an amylopullulanase which could hydrolyse raw starch under a broad
range of conditions [108]. From Bacillus sp. TS-23, the amylase was reported to
hydrolyse raw starch with concomitant production of maltotriose, maltotetraose and
maltopentaose [62]. Such alkaline-active, raw starch-degrading amylases are therefore most suitable for application in surface sizing and coating of paper using starch.
4.6 Textile Industry
During the process of weaving the yarn in the textile industry, the warp threads are
exposed to extensive mechanical strain. To avoid breakage, the warp threads
are coated using a gelatinous compound in a process referred to as “sizing”. Starch,
either native or modified, is commonly used for sizing as it is a cheap, readily
available polymer and can easily be removed from the fabric after the weaving
process. Subsequently, after sizing with starch, the coated warp threads are not able
to absorb water or finishing agents such as dyes and other chemicals used in the
textile industry. As such, the starch needs to be removed from the warp. This is done
by a process known as “desizing”. The process was conventionally carried out using
oxidizing agents such as ammonium persulfate or hydrogen peroxide at high pH
and temperature. This process has limitations as it does not efficiently remove the
starch and resulted in a fabric with reduced tensile strength. Furthermore, use of
chemicals is costly and harmful to the environment and would subsequently require
effluent treatment and disposal. An alternative is the use of alkaline-active amylases
that catalyse hydrolysis of starch to water-soluble dextrins which are then removed
by washing at mildly alkaline conditions. These enzymes efficiently remove
the starch coating without damaging the fabric. The enzyme PrimaGreen
® ALL
from DuPont
™ has been engineered to desize textiles throughout a much broader
spectrum of operating conditions including temperature ranging from 20 to 105
C
and pH of 6–10.
4.7 Alkaline Waste Water Treatment
Various industries generate waste waters that are toxic, rich in heavy metals and
dyes, highly acidic or highly alkaline. The paper and pulp, textile and potato
processing industries generate alkaline waste water with pH greater than 10. In a
study conducted in India, alkaliphilic microorganisms were isolated from textile
waste water and were found to neutralize the alkaline industrial waste waters [109].
It was postulated that these microbes were able to neutralize the pH by producing
acids through their carbohydrate metabolism by alkaline-active amylases. Thus,
these enzymes are suitable combined with microorganisms that can metabolize
236
S. O. Hashim
The thermophilic and alkaliphilic Bacillus sp. strain XAL601 was reported to
produce an amylopullulanase which could hydrolyse raw starch under a broad
range of conditions [108]. From Bacillus sp. TS-23, the amylase was reported to
hydrolyse raw starch with concomitant production of maltotriose, maltotetraose and
maltopentaose [62]. Such alkaline-active, raw starch-degrading amylases are therefore most suitable for application in surface sizing and coating of paper using starch.
4.6 Textile Industry
During the process of weaving the yarn in the textile industry, the warp threads are
exposed to extensive mechanical strain. To avoid breakage, the warp threads
are coated using a gelatinous compound in a process referred to as “sizing”. Starch,
either native or modified, is commonly used for sizing as it is a cheap, readily
available polymer and can easily be removed from the fabric after the weaving
process. Subsequently, after sizing with starch, the coated warp threads are not able
to absorb water or finishing agents such as dyes and other chemicals used in the
textile industry. As such, the starch needs to be removed from the warp. This is done
by a process known as “desizing”. The process was conventionally carried out using
oxidizing agents such as ammonium persulfate or hydrogen peroxide at high pH
and temperature. This process has limitations as it does not efficiently remove the
starch and resulted in a fabric with reduced tensile strength. Furthermore, use of
chemicals is costly and harmful to the environment and would subsequently require
effluent treatment and disposal. An alternative is the use of alkaline-active amylases
that catalyse hydrolysis of starch to water-soluble dextrins which are then removed
by washing at mildly alkaline conditions. These enzymes efficiently remove
the starch coating without damaging the fabric. The enzyme PrimaGreen
® ALL
from DuPont
™ has been engineered to desize textiles throughout a much broader
spectrum of operating conditions including temperature ranging from 20 to 105
C
and pH of 6–10.
4.7 Alkaline Waste Water Treatment
Various industries generate waste waters that are toxic, rich in heavy metals and
dyes, highly acidic or highly alkaline. The paper and pulp, textile and potato
processing industries generate alkaline waste water with pH greater than 10. In a
study conducted in India, alkaliphilic microorganisms were isolated from textile
waste water and were found to neutralize the alkaline industrial waste waters [109].
It was postulated that these microbes were able to neutralize the pH by producing
acids through their carbohydrate metabolism by alkaline-active amylases. Thus,
these enzymes are suitable combined with microorganisms that can metabolize
236
S. O. Hashim