and render the process environmentally benign [73]. Moreover, the reduction in the
alkali concentration improves the quality of the cotton fiber [74] and subsequently
enhances the textile quality.
Bast Fiber Degumming
Bast fibers which are known for their high tensile strength have been used for
thousands of years in making ropes, cloths, yarn, bags, and sails, while in recent
times, bast fibers are used to manufacture different items ranging from building
materials to plastic composites [75, 76]. For instance, blended hemp, flax and kenaf
fibers have been used as a natural insulating material that competes with the
traditional fiberglass insulation [77]. However, the bast fiber should be recovered
from the biomass to be used in these applications. Like cotton scouring, the bast fiber
recovery process involves the removal of cementing substances that cover and
bundle the cellulosic fibers. This process of removing the gummy substance is
known as degumming. The traditional degumming process uses up to 20% (w/v)
sodium hydroxide solution containing some wetting and reducing agents [78]. The
plant biomass will be soaked for 1 day in this alkaline solution and then boiled for
about 4 h to dissolve the gummy substance and release the fibers. After boiling, the
fibers will be extensively washed and neutralized. As in the case of the cotton
scouring process described above, the high concentration of sodium hydroxide, the
boiling of the suspension, and the accompanied extensive washing and neutralization make the process not only expensive but also time-consuming and polluting.
The use of enzymes that allow to recover the fibers at reduced concentration of
sodium hydroxide and energy consumption can make the process more attractive
from environmental as well as economic stands.
Alkaline active pectinases have been successfully tried to degum flax, ramie, jute,
and hemp fiber [79, 80]. The use of enzymes allows to reduce the sodium hydroxide
concentration, shorten the soaking time, and lower the cooking temperature used to
release the fibers. Diluted alkali is often implemented in the degumming process
which, in addition to preventing the growth of cellulose-degrading contaminants,
helps to remove effectively the lignin components from the fibers, and this minimizes the consumption of bleaching chemicals in the subsequent steps. Thus, the
enzymes used to degum the fibers should be operationally stable at high pH. Such
enzymes are often obtained from alkaliphiles [80–82].
Biostoning
Textile fiber-modifying enzymes have been used in the finishing of fabrics and
clothes in a process known as biopolishing. A prominent application in this area is
biostoning of denim. Denim jeans dyed with synthetic indigo seems to be one of the
most popular garments. Due to the fashion desire, denim garments are often subject
to wash cycles that give the garments a slightly worn look. In early conventional
14
G. Mamo and B. Mattiasson
alkali concentration improves the quality of the cotton fiber [74] and subsequently
enhances the textile quality.
Bast Fiber Degumming
Bast fibers which are known for their high tensile strength have been used for
thousands of years in making ropes, cloths, yarn, bags, and sails, while in recent
times, bast fibers are used to manufacture different items ranging from building
materials to plastic composites [75, 76]. For instance, blended hemp, flax and kenaf
fibers have been used as a natural insulating material that competes with the
traditional fiberglass insulation [77]. However, the bast fiber should be recovered
from the biomass to be used in these applications. Like cotton scouring, the bast fiber
recovery process involves the removal of cementing substances that cover and
bundle the cellulosic fibers. This process of removing the gummy substance is
known as degumming. The traditional degumming process uses up to 20% (w/v)
sodium hydroxide solution containing some wetting and reducing agents [78]. The
plant biomass will be soaked for 1 day in this alkaline solution and then boiled for
about 4 h to dissolve the gummy substance and release the fibers. After boiling, the
fibers will be extensively washed and neutralized. As in the case of the cotton
scouring process described above, the high concentration of sodium hydroxide, the
boiling of the suspension, and the accompanied extensive washing and neutralization make the process not only expensive but also time-consuming and polluting.
The use of enzymes that allow to recover the fibers at reduced concentration of
sodium hydroxide and energy consumption can make the process more attractive
from environmental as well as economic stands.
Alkaline active pectinases have been successfully tried to degum flax, ramie, jute,
and hemp fiber [79, 80]. The use of enzymes allows to reduce the sodium hydroxide
concentration, shorten the soaking time, and lower the cooking temperature used to
release the fibers. Diluted alkali is often implemented in the degumming process
which, in addition to preventing the growth of cellulose-degrading contaminants,
helps to remove effectively the lignin components from the fibers, and this minimizes the consumption of bleaching chemicals in the subsequent steps. Thus, the
enzymes used to degum the fibers should be operationally stable at high pH. Such
enzymes are often obtained from alkaliphiles [80–82].
Biostoning
Textile fiber-modifying enzymes have been used in the finishing of fabrics and
clothes in a process known as biopolishing. A prominent application in this area is
biostoning of denim. Denim jeans dyed with synthetic indigo seems to be one of the
most popular garments. Due to the fashion desire, denim garments are often subject
to wash cycles that give the garments a slightly worn look. In early conventional
14
G. Mamo and B. Mattiasson