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"Summary on advanced methods used in degu mming process of ramie and silk"
Method · June 2024
DOI: 10.13140/RG.2.2.15204.80006
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武汉纺织大学
WUHAN TEXTILE UNIVERSITY

Written On
“Summary on advanced methods used in degumming process of ramie and silk”

Submitted By:
Sourav Kumar Das
School Of Textile Science and Engineering


Summary on advanced methods used in degumming process of ramie and silk
Introduction:
Degumming is the process of removing the sericin, a sticky substance produced by the silkworm
that holds the strands of silk together. It is also known as silk scouring. Removing the gum
improves the lusture, color, hand, and texture of the silk. As much as one-third of the weight may
be lost when the gum is removed.In this study we will discuss about the advanced methods used
in degumming process of ramie and silk as well as their advantages and limitations. Ramie
provides the longest and strongest natural fiber in textile industry, but its traditional degumming
process is costly and requires a large amount of alkali, which causes serious environmental
concerns. Degumming of eri silk cocoons was carried out using three different concentrations of

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sodium carbonate and neutral soap along with three different duration of boiling following Box
and Behnken design of experiment. Higher amount of degumming loss was observed with more
sodium carbonate concentration and duration of boiling for both white and brick red eri silk
cocoons. Single fibre tenacity decreases with increase of sodium carbonate concentration as well
as duration of boiling. Degumming of silk involves the cleavage of peptide bonds of sericin,
either by hydrolytic or enzymatic methods, and the subsequent removal of sericin from the silk
fibroin. Hydrolysis of sericin can be carried out under neutral, alkaline or acidic conditions to
give four fractions, each having different properties. Boiling-off in alkaline soap solution is the
most popular degumming method.There are many qualitative methods of assessing the extent of
degumming; however, quantitative methods have yet to be developed. Degumming can be
carried out on yarn or fabric, in manually or mechanically operated machines. Mechanisms of
degumming remain to be investigated [1].

Keywords: Degumming, silk, ramie, enzyme, Bio-degumming, Microwave irradiation, Eco-
friendly.

Discussion on advanced degumming Process of ramie:
1.Through enzymatic treatment :
Bast fibers from ramie (Boehmeria) were treated with cell-free culture supernatants a
recombinant strain expressing to investigate the degumming effects of different extracellular
polysaccharide-degrading enzymes. Culture supernatants from the with high pectate lyase
activities were most effective in fiber separation and reduced the gum content of ramie fibers by
30% within 15 h. Xylanase activity produced by the Amycolata sp. contributed little to the
degumming. Electron micrographs showed that the crude pectate lyase from the Amycolata sp.
removed plant gum more efficiently from decorticated ramie bast fibers than the purified
enzyme. Similarly, degumming with the crude enzyme of the Amycolata sp. and the recombinant
strain for 24 h resulted in fibers with a residual gum content of 14.7 and 17.3%, respectively.
Degumming with the crude enzyme of the recombinant Streptomyces strain was slightly
improved by the addition of a commercial pectinesterase.

Methods:
The Amycolata sp. was grown in a flask using medium 52 at neutral pH and 30°C on a rotary
shaker at 150 rpm.All the polysaccharides were obtained from Sigma S. li6idans harboring the
plasmid pIJ702 with and without the pel gene of the Amycolata sp.was grown in medium. At the
end of the incubation period cultures were centrifuged at 10 000_g and 4°C for 20 min and the
cell-free culture supernatant was designated as crude enzyme. A stirred Amicon cell (Amicon,

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Danvers, MA) equipped with an Amicon PM1 membrane was used for concentrating cell-free
culture supernatant up to 5-fold.Out in 100 ml Erlenmeyer flasks using 0.5 g of decorticated
dried ramie fibers and 20 ml of the crude enzyme (pH 7) from 3 days old liquid cultures
(supplemented with 0.01% sodium azide).Flasks were shaken at 150 rpm at room temperature
for 15 h. The gum content of the fibers from two independent experiments was determined
gravimetrically by sequential degumming of the fibers with hot sodium hydroxide solutions of
increasing concentrations[2].

Fig-1: SEM view after degumming treatment
Advantages:
This method is eco friendly treatment and the flexibility of ramie fibers also increased.
Limitations:
Need to maintain proper parameters like pH and temperature, otherwise this process will work
less or not properly.
2. Green degumming process of ramie:
Ramie provides the longest and strongest natural fiber in textile industry, but its traditional
degumming process is costly and requires a large amount of alkali, which causes serious
environmental concerns. In the current work, a steam explosion (STEX) treatment followed by
sodium percarbonate (SP) soak degumming process was investigated. Microstructure, chemical

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composition and mechanical properties of the refined ramie fibers were comprehensively
characterized. The residual gum content was below 5%, the fineness was higher than 1600 Nm
(6.25 dtex), the breaking tenacity was 5.4 cN/dex, and the whiteness was above 50%. All of the
properties met the requirements of Chinese national standard, and the breaking tenacity and
whiteness were notably better than those of the fibers degummed traditionally. In addition,
environmental impacts of the new degumming process were evaluated. Only 50% chemicals
were needed for the new process, and chemical oxygen demand (COD) of the waste reduced to
35% of the traditional method. Therefore, the new method was more environment-friendly
and economically feasible. It has great potential for industry applications.
Methods:
The ramie bast samples were supplied by the Research Center of Bast-fiber Plant in Hunan
Province, China. All the ramie material was tiled under the ambient conditions (20–30 °C
and<50% humidity). The STEX-SP treatment includes the following three steps:Peracetic acid
(PAA) presoak: Ramie (30 g) and PAA (concentration 2%, LSR 12:1, pH 5.0) were soaked at 55
°C for 10 min. The PAA solution could be reused for 6–8 batches.STEX treatment: The STEX
treatment on presoaked ramie was conducted at 0.5 MPa for 5 min. SP soak: Pretreated ramie,
SP (concentration 2%, LSR 12:1) and additives reacted at 90 ± 5 °C for 1 h. The additives
include 3% hydrogen peroxide, 3% NaSiO3 and 2% Sodium polyphosphate[3].

Fig. 2: Physical properties of (A) raw ramie bast; (B) ramie fibers treated with traditional alkali
degumming; (C) ramie fibers treated with STEX only; (D) ramie fibers treated with STEX-SP
degumming

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Advantages:
The gum content, fiber fineness, fiber breaking tenacity and whiteness are major indexes to
evaluate the degumming quality in textile area is high.Comparable same or better values of the
above indexes are essential for the new degumming method.

Limitations:
The gum content of the raw ramie bast was 25.9%. It reduced to 11.6% after the STEX treatment
and below 5% after the SP soaking. The result met the requirement of Chinese national standard
and was close to that of the traditional alkali degumming process comparatively a little less.





3.Alkalophilic bacteria and their polysaccharide-degrading enzymes for ramie
degumming:

Three strains of alkalophilic bacteria, Bacillus sp. NT-39, NT-53 and NT-76, were selected for
the degumming of ramie fibers and production of polysaccharide-degrading enzymes. After 48 h
of incubation with the strains, the loss of the gum might amount to 5.0% or more of the fibers
and a number of polysaccharide-degrading enzymes were secreted to the culture supernatants.
The residual gum of the fibers decreased to 9.4% after 5 h of enzymatic degumming. Analysis of
gum contents and enzyme activities revealed that pectate lyase and xylanase played an important
role in the degradation of residual gum. Enzymatic degumming resulted in an increment of 5.4
ISO units in fiber brightness, whereas the reduction in bundle breaking tenacity of the fibers was
less than 5.0%. The results confirmed that degumming of ramie fibers by alkalophilic bacteria
and their enzymes had substantial advantages.

Preparation of alkali-soluble gum from ramie Fibers:

100 g of decorticated ramie fibers was extracted with 1 dm3 solution of 1% Na2CO3 at 100°C
for 20 min. The extract was precipitated with acetone, then the precipitate was washed with 95%
ethanol and anhydrous ethanol. After filtration, the alkali-soluble gum was dried in a vacuum
desiccator.

Screening of strains utilizing alkali-soluble gum:

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The selective medium containing 30 g of alkali-soluble gum, 1 g of K2HPO4, 3 g of NaNO3, 18
g of agar in 900 cm3 of H2O was autoclaved at 121°C for 20 min and adjusted to pH 10.0 with a
sterilized solution of 10% Na2CO3 at 60°C before pouring into plates. 80 strains of alkalophilic
bacteria were applied to the plates. After incubation at 37°C for 24 h, the strains that grew
vigorously were picked and transferred to the plates again and incubated under the above
conditions. The strains forming colonies of >1.0 cm were selected for the degumming test.

Bacterial degumming:

Bacterial degumming was conducted as follows: a loop of each selected strain was inoculated
into a 250 cm3 Erlenmeyer ¯ask containing 5 g of the ramie fibers pretreated with 50 cm3
mineral salt solution (K2HPO4, 1 g:NaNO3, 3 g: Na2CO3, 10 g dm3 of H2O pH 10.0) at 100°C
for 20 min. The asks were incubated at 37°C for 24±48 h with shaking at 180 rpm. The ramie
fibers were then washed thoroughly with tap water on a 120-mesh screen and dried at 105°C.
The degumming liquor could be used as inoculum if necessary. The experiments were performed
in triplicate and the means are reported. Enzymatic degumming was conducted in 150 cm3
Erlenmeyer asks with cell-free supernatants (adjusted to pH 10.0 with a solution of Na2CO3)
from 48 h-old degumming liquors. Each ask contained 50 cm3 of the supernatant and 5 g of the
ramie fibers (pretreated with a solution of 1% Na2CO3 at 100°C for 20 min). After
incubation at 40°C for 5 h, the fibers were washed and dried as described in bacterial
degumming [4].



Advantages: Although some attempts to degum ramie fibers with neutrophilic microorganisms
and their enzymes have been made, their industrial applications are rather limited. High
production cost and low degumming efficiency are the major problems hindering the application
of this biotechnology. It has been reported that the degumming process can be accelerated
by pretreating ramie fibers with alkali

Limitations: In order to know what was the effect of pretreatment on the bacterial degumming,
the untreated fibers were incubated with the degumming liquor of strain NT-39.The results
showed that a long degumming course.



4.Through Triboelectric Nanogenerator

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One of the strongest and oldest natural fibers, ramie fiber has been widely used for fabric
production for at least six thousand years. And degumming is a critical procedure that has been
developed to hold the ramie fiber’s shape, reduce wrinkling and introduce a silky luster to the
fabric appearance. Herein, we introduce a fundamentally new working principle into the field of
ramie fiber degumming by using a triboelectric effect. Resort to a water-driven triboelectric
nanogenerator (WD-TENG), the ramie fibers degumming efficiency was greatly enhanced with
improved fiber quality, including both surface morphology and mechanical properties.
Furthermore, it saves the chemicals usage in the traditional method, which makes it a green and
practical approach to fully remove the noncellulosic compositions from ramie fibers. In addition,
as a systematical study, the WD-TENG was further employed as a sustainable power source to
electrochemically degrade the degumming wastewater by recycling the kinetic energy from
flowing wastewater in a self-powered manner. Under a fixed current output of 3.5 mA and
voltage output of 10 V, the self-powered cleaning system was capable of cleaning up to 90 % of
the pollutants in the wastewater in 120 min. Given the compelling features of being self-
powered, environmentally friendly, extremely cost-effective, good stability, high degumming
and degradation efficiency, the presented work renders an innovative approach for natural fiber
extraction, and could be widely adopted as a green and innovative technology in textile industry.


Powered Integration Electrochemical System for Ramie Degumming.

The WD-TENG was connected to the central shaft of a miniature water turbine. Normal tap
water was directed into the turbine inlet through a plastic pipe. A Ti/PbO2 anode and a Ti
cathode were immersed in the reaction pond. A power management circuit was connected to
output end of the WD-TENG to convert the alternating current to direct current signals. And a
pH controller was employed to monitor the pH values in the reaction solution. The degumming
experiments were conducted in a 500 mL beaker filled with 10.0 g raw ramie fiber and 100 mL
freshly prepared degumming solution, continuously mixed at 200 rpm with magnetic stirred bar.
The reaction temperature was raised to be 100 ℃. Then the degumming reaction process was
conducted and the reaction time was recorded. The treated fibers were thoroughly washed with
deionized water. Finally they were squeezed and properly dried at oven (100 ℃, 3 h) before a
further surface characterization and mechanical properties measurement[5] .

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Fig-4: Integration Electrochemical System for Ramie Degumming
Advantages:
By harvesting the kinetic energy from ambient water flow, the generated electric field from the
WD-TENG can largely boost the migration of hydroxyl ions and enhance the electrolysis effect,
which can greatly improve the degumming speed and degumming efficiency.

Limitations:
Not so much user friendly for all level of users.

5.Pectinolytic Enzymes from Actinomycetes process for ramie:
Actinomycetes isolated from 10 different soil and compost samples were screened for production
of pectinolytic enzyme activities when grown on pectin-containing solid and liquid media.
Pectinolytic enzymes,detected by using plate diffusion tests with a medium containing ramie
(Boehmeria nivea) plant material as the sole carbon source, were mainly pectatelyases, but low
activities of pectinesterases were also observed.Polygalacturonases and polymethyl
galacturonases were not produced. Multiple forms of pectate lyases were detected in the culture
supernatants of some of the strains by using the zymogram technique of isoelectric focusing gels.

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Xylanolytic and cellulolytic activities were always found to be associated with pectinolytic
activities. None of the pectinolytic enzymes were produced in a medium with glucose as the sole
carbon source.Treatment of ramie bast fibers with crude enzyme preparations from a selection of
strains showed a good correlation between the pectatelyase activity applied and the degumming
effect, resulting in good separation of the bast fibers.

Detection of pectinolytic actinomycetes.

Colonies from PYG plates were picked and transferred to DMC plates (17) containing 0.5%
citrus pectin (Sigma) instead of glucose. After 3 days of incubation at 30°C, plates were stained
with 0.05% aqueous ruthenium red [6].

Advantages: Pectate lyases were the dominant pectinolytic enzymes in 79 isolates of
actinomycetes grown in liquid cultures with ramie fibers as the sole carbon source. Most of the
pectinolytic isolates also produced very low levels of pectinesterases.

Limitations:A larger number of pectinolytic strains was detected on solid medium by ruthenium
red staining than in liquid cultures by the plate diffusion test. This could be explained by the
different medium compositions and different cultivation conditions.






6. Isolated Bacillus pumilus DKS1method for ramie

A combined (enzymatic and chemical) process using a Bacillus pumilus strain (DKS1), isolated
from the soil, was used to degum ramie bast fibres. After 24 h of incubation with the isolated
pectinolytic strain using a low cost medium, the weight loss of the ramie fibre was found to be
25% under small scale. High activity of pectatelyase was detected in the culture supernatants;
400 kg of ramie fibres was degummed with 24% weight loss in large-scale degumming under
Weld conditions. No cellulase activity was found. Microbial intervention followed by mild
(0.1%) alkali treatment showed high percentage of weight loss from the ramie fibre. Bacterial
degumming followed by chemical treatment resulted in an increase of single fibre tenacity
(cN/tex) by more than 20.81% as compared to non degummed (decorticated) fibre samples.
Scanning electron micrographs (SEM) and Xuorescence microscope showed that after Bacillus
pumilus DKS1 treatment the surface of the decorticated ramie fibre becomes very smooth. These

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results indicate the process provides an economical and eco-friendly method for the small scale
as well as large scale degumming of decorticated ramie fibre. This study has great relevance to
the textile as well as paper industry.

Methods:
The pectate lyase activities were determined by the TBA (thiobarbituric acid) assay which
measured absorbance at 550 nm. Suitable dilutions of the supernatant (1 ml) were added to 5 ml
of PGA (polygalacturonic acid, sodium salt) solution (0.75%, w/v). The assay volumes were
made up to 10.0 ml with Tris–HCl buVer (25 mM, pH 8.5) containing 1 mM CaCl2 and
incubated at 75°C for 2 h. About 0.6 ml zinc sulphate (9.0%, w/v) and 0.6 ml sodium hydroxide
(0.5 M) were then added. The samples were centrifuged (3,000*g, 10 min) and 5.0 ml of the
clear supernatant was added to a mixture of thio-barbituric acid (3.0 ml, 0.04 M) and HCl (1.5
ml, 0.1 M). The mixture was heated in a boiling water bath for 30 min, and the absorbance of the
coloured solution was measured at 550 nm against a reference cuvette which contained the same
reagents as that of the experimental cuvette but for which the zinc sulphate and sodium
hydroxide were added before adding the enzyme and substrate. One unit of activity was defined
as the amount of enzyme that caused a change in absorbance of 0.01 under the conditions of the
assay [7].

Bleaching of degummed ramie fibre:
The degummed ramie fibres were immersed in an alkaline hydrogen peroxide solution for
approximately 1 h or until the desired bleach or whiteness was obtained at room temperature.
The bleaching solution contained sodium hydroxide (0.1%), EDTA (0.5%) and H2O2 (0.5%).
The liquor to Wbre ratio was 10:1 (w/v). The bleached degummed ramie bast fibre was rinsed
under tap water and dried at 80°C.

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Fig-5:Fluorescence microscopy of decorticated, control, degummed and bleached ramie fibre under Bright field.

Advantages:
For natural fibres, the fineness throughout each fibre was not constant and fibre-to-fibre variation
was much higher. Due to the large variation in fineness in a single fibre, the single-fibre tenacity
was considered as the tenacity per unit fineness of the fibre.

Limitations:
Tenacity or tensile strength of the fibre is a not very important parameter for grading for
industrial purposes in this study.

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7.Rapid process of ramie bio-degumming by Pectobacterium:

Factory tests for rapid process of ramie bio-degumming by Pectobacterium sp.CXJZU-120 were
conducted and evaluated comparing the processes of traditional chemical degumming and bio-
chemical degumming.Results revealed that over 90% of the gum in raw ramie could be removed
only with Pectobacterium sp. CXJZU-120 in 6 h. The rapid process was not only suitable for the
extraction of ramie fibers from different grades of raw material and retaining the inherent
morphological structures and textile properties, but also could reduce the production cost up to
20.5%, raise resource utilization by more than 50% and reduce pollution charge by more than
80% compared with the traditional chemical degumming. It is a breakthrough in the degumming
of ramie and has great application potential in the extraction of herbaceous fiber materials.

Methods:

Compared with the wild strain (CGMCC0245), the obvious variation of the improved strain
(CGMCC2194) was that the fermentation products were turned into blue-green considered as the
termination symbol of cultivation or fermentation and the ramie degumming period shortened
from 7–8 hr to 5–6 hr, which was obtained after transforming the plasmid from another strain
Erwinia carotovora LY according to Wu Naihu23 and ultraviolet mutagenesis.Bacillus subtilis
T66 (CGMCC, AS1.943) was used as the contrast strain [8].


Advantages: To solve the problem of the shortage of natural resources such as petroleum,
forests and so on, the development of non-cotton and sustainable natural fibers (such as ramie,
flax, jute, hemp and kenaf) has become an uncontrollable trend. Furthermore, there is an obvious
tendency in the manufacturing industry to replace traditional chemical methods with biological
methods, because the latter meets the increasing requirements for environmental protection
better, with more output and less pollution.


Limitations: Factory tests for rapid processing of ramie bio-degumming by Pectobacterium sp.
CXJZU-120 had been conducted in nine ramie process enterprises for 1 month to 5 years.

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8. Novel Chemical Degumming Process for Ramie Bast Fiber
A novel chemical degumming process for ramie fiber was developed, using sodium carbonate
solution with poly(vinyl alcohol) (PVA) as an auxiliary surfactant and sodium triphosphate.
Optimum performance for the degumming of ramie fiber was obtained with sodium carbonate
concentration 30 gm L–1, PVA concentration 2.2 gm L–1, sodium triphosphate concentration 6.0
gmL–1 and temperature 90 °C. The tensile properties of the ramie fibers degummed using
Na2CO3 are comparable with fibers degummed using sodium hydroxide.This new mild, rapid
degumming technique for ramie fiber has a potential application in industry and is less
environmentally polluting than the traditional method. The ramie fibers before and after
degumming were characterized by FT-IR, thermo-gravimetric analysis, differential scanning
calorimetry and scanning electron microscopy. Ramie is a member of the bast family, grown
mainly in temperate and tropical areas, and well known as “China grass” in Western Europe and
America due to the large production in China. As one of the most important natural fibers, the
cellulose content of ramie is higher than in other bast fibers such as hemp, flax and jute. Ramie
produces one of the strongest and longest plant fibers and is lustrous with an almost silky
appearance. Thus ramie fibers are used for clothing fabrics, industrial packaging, twines,
cordage, canvas, car outfits, etc..However, the stem of ramie contains a large amount (20–30
wt%) of gummy matter comprising pectin and other non-cellulosic materials. The gummy
substance is commonly amorphous with a degree of polymerization of 200–400 [9].

Fig-6: SEM micrographs of ramie (a, 300×) and ramie fiber
Advantages:
The biomass of ramie can be successfully degummed in sodium carbonate solution with PVA
and sodium triphosphate.The process is mild compared to the traditional chemical degumming
process. The tensile properties of the degummed ramie fiber were comparable to those of ramie
degummed using sodium hydroxide, which is traditionally used. Thus, this mild, rapid
degumming technique with NaCO3 for the biomass of ramie has potential application in
industry, and further work is ongoing.

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Limitations:
The stress of ramie fiber degummed in sodium carbonate solution were greater than the
corresponding properties of ramie degummed in NaOH, and there was almost the same
amount of gum residue from the two methods of treatment.

Discussion on advanced degumming Process of Silk:
Silk is a natural protein filament that can be converted into textile by either knitting or weaving
techniques. The protein fibre/filament of silk is composed mainly of fibroin and produced by
certain insect larvae to form cocoons. For commercial use it is almost entirely limited to filament
from cocoons produced by the caterpillars of several moth species belonging to the genus
Bombyx and commonly called silkworms reared in captivity (sericulture). The shining
appearance of silk is due to the triangular prism-like structure of the silk fibre, which allows silk
cloth to refract incoming light at different angles, thus producing different colors. Silks are
produced by several other insects, but generally only the silk of moth caterpillars has been used
for textile manufacturing. A feature on silk fibre prospect in Bangladesh, present scenario and
problems of sericulture was published in Bangladesh Textile Today (Issue: May-June 2010). It
can be helpful for further reading about silk.

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Physical Structure & Composition:

Silk is the only natural filament. It is a solid fiber. The filaments are 300-1800 yards long. Silk fiber has a
double rod-like structure, covered with lumps of gum. Wild silk fiber is very irregular and resembles
flattened, wavy ribbons with longitudinal markings. Cultivated silk is smooth, cylindrical and generally
uniform in thickness, like glass rods.
Chemical Composition of Silk Fibre: (Approximate value)
 Fibroin 76%
 Sericin 22%
 Fat & wax 1.5%
 Mineral salt 0.5%
 Silk fibre contains approximately 20-25 percent Sericin gum. Sericin is a group of soluble
glycoproteins expressed in the middle silk gland of Bombyx mori. Silk emitted by the
silkworm consists mainly of two proteins, sericin and fibroin; fibroin being the structural
center of the silk, and sericin being the gum coating the fibres and allowing them to stick
to each other. The chemical composition of sericin is C30H40N10O16.


Degumming Silk Cocoons:
The natural gum, sericin, is normally left on the silk during reeling, throwing and weaving. It acts as a size
which protects the fibres from mechanical injury. After the moths emerge, the cocoons must be
degummed before they can be spun into yarn.Degumming is the process of removing the sericin, a

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sticky substance produced by the silkworm that holds the strands of silk together. It is also known as silk
scouring. Removing the gum improves the lusture, color, hand, and texture of the silk.As much as one-
third of the weight may be lost when the gum is removed. Raw silk with the gum still on the filament is
called ‘Hard silk’. Degummed silk is ‘soft silk’.Silk degumming can also be accomplished by treated with
different alkaline, neutral and acid proteases (Enzymes).

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2. Application of Low-Pressure Plasma Pretreatment in Silk Fabric Degumming Process

A novel and effective method was developed for raw silk fabric degumming with the application
of low-pressure argon plasma in pretreatment combining a subsequent one-step mild wet-
chemical process. The plasma parameters, such as argon pressure ,discharge power and exposure
time, were optimized according to degumming loss and the properties of fabric such as capillary
rise, tensile strength, bending rigidity, etc. An optimized plasma pretreatment for raw silk fabric
degumming was at 80 Pa of argon gas and 60 W glow discharge power for 5–10 min. The raw
silk fabric and fibers pretreated by argon plasma were characterized by scanning electronic
microscopy and X-ray powder diffraction. In comparison with a conventional degumming
process, the proposed method achieved comparable degumming efficiency and properties of silk
fabric, and it was more environmentally friendly by shortening the conventional wet-chemical
treatment process, saving the dosage of degumming agents, water and energy.

Low-Pressure Plasma System methods:

A schematic diagram of low-pressure plasma system (HD-1, Suzhou Hongda plasma technology
company, China) was employed for raw silk fabric/yarns pretreatment, A cylindrical quartz
chamber (with a dimension of U23 cm 9 H30 cm) and two parallel electrodes were used. Glow
discharge was supplied by a 13.56 MHz power source (RF discharge). Raw silk fabric or yarns
were hung vertically with a sample stand between the two parallel electrodes. Argon plasma
treatment pressure ranged from 20 to 100 Pa, glow discharge power input was varied from 20 to
120 W, and exposure time. A commercial mulberry raw silk fabric (Habutai, with a fabric weight
of 90.6 g m-2 and a fabric density of 32 ends cm-1 , 24 picks cm-1) was used in this study. The
raw silk fabric was cut into a dimension of 20 cm 9 20 cm, and used as received without any
other previous treatment. All the silk fabric samples were conditioned at 20 ± 2_C and 65 ± 3%
relative humidity for 24 h before any weight measurement or testing. Typical raw silk yarns of
20/22 D were also treated by argon plasma at optimum conditions for the surface morphological
investigations.All chemicals used in degumming process, such as sodium carbonate, sodium
silicate, sodium dithionite, Marsille soap, dispersing agent MF, were commercial products. A
pure argon gas (99.99 vol.%) was used in plasma treatment [10].

19. Page 18 of 24


Fig-7: Schematic diagram of low-pressure plasma system

Advantages:
Well agreed with the results about the discharge power effect on fabric weight loss by
Degumming.The main properties of degummed silk fabric, such as fabric whiteness and capillary
rise height, were also improved with the increased discharge power up to 60 W and then
decreased.

Limitations:
Raw silk fabric was pretreated at various exposure times with 80 Pa gas pressure and 60 W
discharge power before a wet chemical degumming process.

3.Degumming of Persian silk by ultrasound and enzymes as a cleaner

Degumming is a surface modification process of natural fibers such as silk. In this paper, the
feasibility of degumming with ultrasonic, ultrasonic–soap, and ultrasonic–enzyme (alcalase,
savinase, and mixtures of these enzymes) processes as cleaner and environmentally friendly
surface modification techniques of Persian silk were investigated. The effectiveness of
parameters such as sonication time, soap, ultrasound enzyme, enzyme concentration, degumming
time and enzymes mixture on silk degumming were studied. The evaluation of the data was
carried out through the measurement of the weight loss, strength, and elongation of the samples.
In addition, the enzymatic treatment improved the properties of silk yarn such as strength and
elongation. The scanning electron microscope images were obtained for degummed silk samples.

20. Page 19 of 24

Methods:
Silk degumming was performed in Ahiba 1000 with raw silk yarn. The details of the experiments
used for degumming with ultrasound–soap, ultrasound–enzyme, and ultrasound mixture of
enzymes are given. Raw silk yarns were treated by ultrasound with 5 g/L sodium bicarbonate
(pH 8–9), and 5 g/L Irgasol NA at 60 degree celcius and 90 min with an L:R value of 30:1.Silk
yarns were treated by ultrasound with 5 g/L sodium bicarbonate (pH 8–9), and 5 g/L Irgasol NA
at 60 degree celcius for 15, 30, 60 and 90 min with an L:R value of 30:1. Then, the samples
were treated by 5 g/L Marseille soap at 100 degree Celsius for 15 min. The effect of ultrasound
on the degumming of silk was conducted at different conditions. Results showed that the weight
loss and strength loss of silk samples are negligible. Therefore, ultrasound on silk degumming
does not have considerable effect on silk degumming [11].

Advantages: The applicability of ultrasound, ultrasound–enzymes, particularly mixtures of
enzymes (alcalase and savinase), to the effective degumming of Persian silk under mild
conditions was investigated.In general, for all the experiments under the specified conditions,
the results show that through the expansion of the treatment time, the amount of sericin
remaining over the samples decreased. In other words, as the treatment time increased, more
sericin was removed from the raw silk samples.

Limitations:
Silk degumming was carried out at different ultrasonic treatment time and degumming time

3. Silk fibers degummed with citric acid
Silk fibers from Bombyx mori silkworm was degummed with different concentration of citric
acid and the physical properties and fine structure were investigated to elucidate the effects of
citric acid treatment.The silk sericin removal percentage was almost 100% after degumming with
30% citric acid which resulted in a total weight loss of 25.4% in the silk fibers. The surface
morphology of silk fiber degummed with citric acid was very smooth and fine, showed perfect
degumming like traditional soap-alkali method. The tensile strength of silk fiber was increased
after degumming with citric acid (507 MPa), where as the traditional soap-alkali method causes
to decrease the strength about half of the control silk fiber (250 MPa). The molecular
conformation estimated by Fourier transform infrared spectroscopy and the crystalline structure
evaluated from X-ray diffraction curve stayed unchanged regardless of the degumming with
citric acid and soap. The dye uptake percentage of silk fiber degummed with citric acid
decreased slightly about 4.2%. On the other hand, the dye uptake percentage of silk degummed
with soap was higher which indicates the disordering of the molecular orientation of the laterally
ordered structure, accompanied with the partial hydrolysis of silk fibroin molecules by the alkali

21. Page 20 of 24

action of soap. The thermal properties were greatly enhanced by soap and citric acid degumming
agents.

Methods:
The effects of the different concentrations of citric acid on silk degumming method were
evaluated.The denier (size), degumming ratio and amount of residual sericin for the silk fibers
treated with different concentration of citric acid at 98 degree celcius for 30 min. Initially, the
degumming ratio of silk fibers increased gradually with raising the concentration of citric acid
and then the value attained to the saturation level, at about 25%, after degummed with above
20% citric acid. The amount of residual sericin which remains on the raw silk fiber decreased
with increasing citric acid concentration. The size of raw silk decreased gradually with
increasing the citric acid concentration. Becker et al. (1995) confirmed that sericin content in B.
mori cocoons varies from 19% to 28% and reported that it gradually declines during cocoon
spinning. From the obtained results we can say that almost all of the sericin was removed after
degumming with 25% citric acid [12].

Advantages:
The domestic silk fibers were degummed with different concentration of citric acid to investigate
the influence of citric acid treatment on degumming process of silk fibers, and the structure,
physical properties and dyeability were compared with traditional soap-alkali degumming
method.

Limitations:The toxicity inside fibers a bit increased.

4.Degumming of silk fabrics with tartaric acid

The effectiveness of the tartaric acid degumming process for silk has been evaluated as a
function of temperature, time and acid concentration in the degumming bath. The degummed
samples were characterised as regards physico-mechanical properties (tenacity, elongation at
break, modulus of elasticity) and intrinsic viscosity. Dyeability with acid, metal-complex and
reactive dyes has been determined spectrophotometrically. The possibility of carrying out
subsequent degummings with the same bath was investigated. The effect of centrifuging and
replenishing the bath with fresh degumming solution was also considered in relation to
degumming efficiency. The results obtained are quite promising as a basis for possible future
industrial application.

22. Page 21 of 24

Materials

Degumming tests on yarn were carried out on 20/22 denier Chinese raw siLk samples, 500 m in
length. Similar tests on fabric were carried out on 100 g/m2 twill fabric samples, 15 x 15 cm (4.5
x 50 cm for physico-mechanical characterisation), having the following specifications: weft
count 75 dtex (3 x 20/22 den), warp count 72 dtex (3 x 20/2 den).

Methods

Alkaline degumming was performed with 7 g/l Marseilles soap, over 60 min at 98"C, liquor ratio
1OO:l. Acid degumming was performed under different conditions of time, temperature and acid
concentration, with 3 g/l nonionic wetting agent, liquor ratio 1OO:l. Degummed samples were
washed with cold and warm water and then dried at room temperature. Weight loss was
measured after conditioning the samples at 20 k 2°C and 65 +/- 2% RH.Centrifuging of the
degumming bath was carried out at 31 0008 for 15 min using a Beckman J2-21 centrifuge (fixed
angle rotor JA-20) [13].

Advantages:
The results of tartaric acid degumming tests on silk yarn, compared with traditional soap
degumming.Weight loss values confirm the effectiveness of tartaric acid as a degumming agent.
Tenacity and elongation values of acid-degummed samples were slightly higher.

Limitations:
A sample of the same fabric degummed with soap was included for comparison.Values obtained
for acid-degummed fabrics were fairly homogeneous.

5.Effect of sodium carbonate concentrations on the degumming and regeneration process of silk
Silk degumming process is regarded as the first key point in the preparation of silk-based
materials. Emphasis of this paper is placed on the effect of sodium carbonate (Na2CO3)
concentrations on degummed silk fibers, the derived aqueous silk solutions, and the final
regenerated silk films. Obvious damage with exposure of silk fibrils was caused at 5% Na2CO3
concentration but no microstructure destruction was observed at 0.005% Na2CO3 concentration.
Weight loss increased dramatically with increasing Na2CO3 concentration, further leading to a
reduction in the degummed silk diameter and poorer thermal stability. Although little change has
been found on β-sheet content of degummed silks differences in molecular weight and
rheological behavior of aqueous silk solutions from different Na2CO3 concentrations are clearly
found which are associated with the subsequent structure and physical properties of the

23. Page 22 of 24

regenerated silk films. The results indicate that there is an inverse relationship between Na2CO3
concentrations and the thermal degradation, wettability, and mechanical properties of
regenerated silk films. Hence, a suitable choice of Na2CO3 concentrations should be seriously
considered to promote the development of different performances and applications of silk-based
materials [14].

Silk Degumming Using Microwave Irradiation
Degumming is a surface modification process of natural fibers such as silk. In this paper, the
feasibility of degumming of Persian silk by microwave irradiation as an environmentally friendly
surface modification technique was investigated.The physical properties of the degummed silk
were investigated. The effectiveness of parameters such as microwave irradiation time,
surfactant, soap, and degumming time on silk degumming were studied. The evaluation of the
data was carried out through the measurement of the weight loss, strength, and elongation of the
samples. The scanning electron microscope images were obtained for degummed silk samples.
The findings of this research support the potential production of new environmentally friendly
textile fibers using microwave irradiation.

Methods:

Silk degumming was performed in Ahiba 1000 with raw silk yarn. The details of the experiments
used for degumming with Marseille soap, Marseille soap-sodium bicarbonate, microwave,
microwave-Marseille soap, microwave-sodium bicarbonate and microwave-Marseille soap-
sodium bicarbonate are given as bellow:

Marseille Soap Degumming

Silk degumming using Marseille soap was performed using with raw silk yarn. Silk yarns were
treated by 10 g/l Marseille soap at 98 oC for 120 min with an L.R value of 30:1.Marseille Soap-
Sodium Bicarbonate Degumming Silk yarns were treated by 5 g/l Marseille soap, and 5 g/l
sodium bicarbonate (pH 9) at 98 degree Celsius for 15, 30, 60, 90, and 120 min with an L.R
value of 30:1.

Microwave Degumming

Raw silk yarns were treated by microwave for 5, 10 and 15 min with an L.R value of 50:1.

24. Page 23 of 24

Microwave-Marseille Soap Degumming

Silk yarns were treated by microwave in the presence of 5 g/l soap for 5 and 10 min with an L.R
value of 50:1.Microwave-Sodium Bicarbonate Degumming Silk yarns were treated by
microwave in the presence of 5 g/l sodium bicarbonate (pH 8-9) with an L.R value of
50:1.

Microwave-Marseille Soap-Sodium Bicarbonate Degumming

Silk yarns were treated by microwave in the presence of 5 g/l soap and 5 g/l sodium bicarbonate
(pH 8-9) with an L.R value of 50:1 [15].

Advantages:
The applicability of microwave at various conditions was investigated to the effective
degumming of Persian silk. In general, for all the experiments under the specified conditions, the
results show that the amount of sericin remaining over the samples decreased.

Limitations
The results show that the weight loss increases by increasing sodium bicarbonate concentration.



Conclusion:
In this study we came to know about different methods of degumming process of ramie and silk
fibers.This methods are advanced and eco-friendly also. The terms 'degumming' and 'boiling-off'
have been used

interchangeably in literature. It has been stated that the

purpose of boiling-off silk
is three-fold: to remove the

sericin, the reagents added by the throwster in soaking

raw silk and
any incidental dirt picked up in any of the

operations of reeling, throwing or knitting.Removal

of natural wax, some colouring components and mineral matter is also achieved during boiling-
off.

25. Page 24 of 24

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regeneration process of silk fibroin. The Journal of The Textile Institute, 2015. 106(3): p. 311-319.
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