Sericin applications: a globular silk protein

Abstract

Sericin is a protein found in silk. This one has different biological functions such as oxidation resistance, antibacterial and antimicrobial activity, and solar ultraviolet radiation (UV) protection, easy absorption and moisture release, inhibition of tyrosine and kinase's activity and cellular additivity, anticoagulants and anticancer properties, and also promotes cell growth and wound healing. In this scientific review article will be reviewed general characteristics of both the fiber of silksilk worm Bombyx mori, and specifically of silk sericin (physico-chemical composition, structural properties and extraction methods). The potential use of sericin in food, drug and cosmetics applications will be also detailed, due to its valuable bioactive properties

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CHEMICAL ENGINEERING - MATERIALS ENGINEERING
Sericin applications: a globular silk protein
INGENIERÍA QUÍMICA - INGENIERÍA DE MATERIALES
Aplicaciones de la sericina: una proteina globular
proveniente de la seda
Jaime A. Barajas-Gamboa*§, Angélica M. Serpa-Guerra*, Adriana
Restrepo-Osorio*, Catalina Álvarez-López*
*Escuela de Ingenierías, Universidad Ponticia Bolivariana. Medellín, Colombia.
§jaimealejandro.barajas@upb.edu.co, angelicaserpa31@gmail.com, adriana.restrepo@upb.edu.co, catalina.
alvarezl@upb.edu.co
(Recibido: Diciembre 05 de 2015 – Aceptado: Abril 05 de 2016)
Abstract
Sericin is a protein found in silk. This one has different biological functions such as oxidation resistance, antibacterial
and antimicrobial activity, and solar ultraviolet radiation (UV) protection, easy absorption and moisture release,
inhibition of tyrosine and kinase’s activity and cellular additivity, anticoagulants and anticancer properties, and also
promotes cell growth and wound healing.
In this scientic review article will be reviewed general characteristics of both the ber of silksilk worm Bombyx
mori, and specically of silk sericin (physico-chemical composition, structural properties and extraction methods).
The potential use of sericin in food, drug and cosmetics applications will be also detailed, due to its valuable
bioactive properties.
Keywords: Applications, protein, sericin, sericulture, silk.
Resumen
La sericina es una proteína que se encuentra en la seda. Esta posee diferentes funciones biológicas tales como
resistencia a la oxidación, actividad antibacterial y antimicrobiana, protección a la radiación solar ultravioleta (UV),
fácil absorción y liberación de humedad, inhibición de la actividad de la tirosina y de la cinasa, aditividad celular,
propiedades anticoagulantes y anticancerígenas, además, promueve el crecimiento celular y la cicatrización de
heridas.
En este artículo de revisión cientíca se examinarán las características generales de la bra de gusano de seda
Bombyx mori y especícamente de la proteína de sericina (composición sicoquímica, sus propiedades estructurales
y los métodos de extracción). También se detallará el uso potencial de la sericina en aplicaciones alimenticias,
farmacológicas y cosméticos, principalmente por el interés que despierta sus valiosas propiedades bioactivas.
Palabras clave: Aplicaciones, proteína, seda, sericina, sericultura.

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1. Introduction
Silk is a natural bre that is produced by silk
worms such as Bombycidae, Saturnidae and
Lasiocampidae (Nagaraju, 2008) and spiders
(Humenik et al., 2011). Mulberry silk, so named
due to they are only fed with mulberry leaves, is
obtained from Bombyx mori (Bombycidae family).
This silk worm needs human care to growth and
reproduction mainly because the way they were
domesticated many years ago.
Sericulture is a labor-intensive industry in which
mulberry tree (Moraceae family, Morus genus)
is grown and silk worms are reproduced. The aim
of this industry is to obtain both yarn and textile
products. This activity includes: egg conservation,
silk worm breeding, prevention of diseases, feed
using mulberry leaves, collection of mature larvae
and transfer to the cocoons formation area (Takeda,
2009). Around de world, 100 thousand tons/years
of silk are produced. China contributes with 70%
of it, followed by Brazil, Japan, India, Thailand and
Vietnam. In Colombia, the silk production is low, and
La Corporación para el Desarrollo de la Sericultura
del Cauca (CORSEDA) is the only producer (20.5
ton/year) in the country (Pescio et al., 2008).
Silkworm needs an especial diet to produce
high quality cocoons and white mulberry leaves
(Morus alba) has a nutritional value that meets
this requirement. These leaves are composed by
water (81.72%), fat (0.57%), protein (1.55%),
bre (1.47%), carbohydrates (14.21%) and other
minor compounds (0.48%), such as minerals
(Capsadel, 1883; Imran et al., 2010). Leaf proteins
are synthetized by cocoon´s gland cells silk, and
right after they are stored into the lumen, where they
are transformed in silk bre. During the pinning
process, this silk passes through the anterior gland
and thereafter it is ejected through the die opening.
The result is a delicate double broin lament, which
is coated by a gum called sericin. This last one, helps
to form the silk cocoon because it acts as a binder
that maintains the structural integrity of this one. The
obtained structure, which has an oval-shaped, is a
safe haven during the larva metamorphosis, process
in which it becomes pupa (Patel & Modasiya,
2011; Takeda, 2009).
2. Silksilk worm life cycle - Bombyx mori
Bombyx mori is a lepidopteran insect that has been
domesticated for more than seven thousand years.
The physiology of these species has been widely
studied due to the economic importance of silk
production throughout the centuries (Nagata &
Nagasawa, 2006). The silkworm life cycle includes
four different stages of metamorphosis: egg, larva,
pupa or chrysalis, and adult (moths). Larval stage
consists of ve stages or ages (Kundu et al., 2008;
Red Andina de la Seda, 2009). The production of
eggs is the rst stage of the metamorphosis. The
female silk worm lays between 300 to 400 eggs at
the same time, and right after she dies; the male
silk worm, on the other hand, lives a bit longer
after this event (Ude et al., 2014). In the second
stage, eggs are incubated for about ten days
until they have hatched into larvae (caterpillars).
Larvae are fed with mulberry leaves in order for
them to store enough nutrients and also be able
to shed their skin ve times. This period lasts
for about four to six weeks until a caterpillar is
formed. The third stage, called pupa or chrysalis,
begins by building the silkworm cocoons, right
after the feeding period is completed (Zhao et
al., 2005). The aim of this cocoon is to protect
the pupa from microbial degradation, natural
drying during metamorphosis, and from potential
predators (Kirshboim & Ishay, 2000).
Silk caterpillar weaves cocoon around itself
continually moving its head as 8 or S, which is
achieved by cyclic bending and stretching their
body. Cocoons are lightweights (only several
grams) and compacts, and they are made of a
single continuous lament silk with a length
between 700-1500 m. These are constructed in 3
days approx. and right after, the silk worm sheds
its skin for the last time and then it becomes pupa.
The cocoon has an ellipsoidal form with the
smallest thickness at its two ends. These points
are pierced with an alkaline substance secreted
by the silk worm, allowing that the invertebrate

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emerges as moth to complete the metamorphosis
(Zhao et al., 2005; Ude et al., 2014; Pescio et al.,
2008).
3. Silk
Silk is the only natural ber available commercially
as a continuous lament. It has a wide range of
textile properties that have made it commendable
to be used in this industry. Some examples are its
nesse, strength, elasticity, dyeability, softness,
exibility, gloss, elegance, and high properties
(Khan et al., 2010; Ude et al., 2014).
3.1 Silk bre structure
Silk ber is mainly composed of two proteins:
broin (70-80%) and sericin (20-30%), and other
minor components such as carbohydrates, waxes
and ash (1.0-2.0%) (Takasu et al., 2002; Mondal
et al., 2007). Moreover, broin is a brillar
protein, which has a semicrystalline structure that
provides stiffness and resistance to ber, while
sericin is an amorphous protein that operates as
a binder to maintain structural integrity of the
cocoon (Humenik et al., 2011; Vepari & Kaplan,
2007; Zhang, 2002).
3.2 Silk transformation
Silk transformation involves different steps to
obtain a silky material, which is characterized
by its softness, length, ne gauge, afnity
dyes, capacity brightness and thermal tolerance
(Burkinshaw & Paraskevas, 2010; Mondal et
al., 2007). This steps are: 1) hot air drying, 2)
“uff” process, 3) cooking, 4) raw silk winding,
5) spool process and 6) degumming. In the rst
step, freshly harvested cocoons are dried at a
temperature of 110-115 °C in order to avoid
the metamorphosis of the silk worm. After this
process, it is recommended to store cocoons for
a period no longer that 40 days, and protect them
from moisture to prevent fungus growth. Before
constructing cocoons, the silkworm produces a
loose woven known as "uff", with the intention
of keeping the cocoon attached to a supporting
structure. This woven, which is 1.5% of the weight
of cocoon is removed in the second step. This
process can be conducted either manually or
using a specialized machine. In the third step,
cocoons are cooked in hot water to expand them
and soften the outer layers of sericin. This process
allows laments being detached easily from them.
Later on, in fourth step, bundles of raw silk are
produced through the merge of several laments
that are twisted to form yarns. These yarns
may have both different thicknesses and twists
depending on the end use. This procedure is done
using a spinning machine. During spool process,
the samples called spinning yarn, are transferred
from ring bobbin or hanks into a package such
as cone and spool, where yarns have the longest
length. This length is achieved by joining several
yarns through small knots (Pescio et al., 2008).
Finally, degumming step is conducted to achieve
high quality dyeing, and to improve both silk
appearance and its application in the textile
industry. This process consists in removing the
sericin from yarns (Martínez & Del Val, 2010).
Traditionally, the degumming procedure not only is
performed with soap in a strongly alkaline medium,
but also alternative procedures are being studied
using other chemical compounds. For example,
some researchers are doing studies on hot water at
high pressures, synthetic detergents, mineral acids,
alkalis and enzymes (Riva et al., 2001).
4. Sericin
Sericin is a cold water insoluble protein, highly
hydrophilic, with adhesive characteristics such
as gelatine. This protein, which has a globular
structure, allows the adhesion of silk laments
to maintain the structural integrity of the cocoon
during its formation (Dash et al., 2007; Hoa et al.,
2012). Furthermore, sericin contains 18 amino
acids where serine (32%), aspartic acid (18%), and
glycine (16%) are the more signicant compounds.
Additionally, this protein is composed of 45.8% of
hydroxy amino acids (serine and threonine), 42.3%
of polar amino acid, and 12.2% of non-polar amino
acids (Shaw & Smith, 1951; Voegeli et al., 1993;
Zhang, 2002). In order to produce biodegradable
materials, sericin can be copolymerized and blended

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along with other polymers. This is possible as the
sericin possesses a strong polar side chains such
as hydroxyl, carboxyl and amino that allow an
easy crosslinking (Nagura et al., 2001).
The molecular weight of sericin depends on its
extraction method. For instance, there is a range
of 40-400 kDa when this is recovered from
cocoons and a range of 80-310 kDa when it is
extracted directly from the gland worm (Wei et
al., 2005). These ranges will depend on their
extraction conditions as the reactive type (acidic,
alkaline, enzymes), and other factors such as
temperature, pressure, pH and the processing
time (Zhang, 2002).
4.1 Properties
Solubility. Sericin is a partial soluble protein in
hot water. It can be classied according to its
relative solubility, using different designations
such as: A and B, or sericin I, II, III, and IV; also
S1, S2, S3, S4, and S5; and α, β, γ modication
(Komatsu, 1996; Voegeli et al., 1993). Depending
on the sericin position within the layer of the
cocoon, other researchers dene two subunits:
α-sericin and β-sericin. The rst one is located
in the outermost layer and it has a high solubility
in hot water. The second one is in the inner layer
and it keeps a low solubility when is compared
with the α-sericin. This difference between these
two subunits can be explained by the presence of
a smaller amount of carbon atoms and hydrogen,
and a greater presence of nitrogen and oxygen in
β-sericin (Bose et al., 1989).
Solubility is also related to the amorphous
and crystalline structure of sericin. The
amorphous region is formed of a random
coil structure, which is the main molecular
conformation of the readily soluble sericin.
The crystalline region, called β-sheet, is
more difcult to dissolve (Dash et al., 2007).
Gel properties. Sericin’s gelation phenomenon,
which was rst investigated in 1994, occurs faster
at low temperatures (10 °C) and pHs about 6-7
(Zhu et al., 1995). An aqueous solution of sericin
forms a gel when random coil structure of the
protein changes to β-given sheet (Aramwit et al.,
2012). This phenomenon is reversible when the
sample is heated into water to 50-60 °C and it
can be gelled again on cooling (Komatsu, 1980).
According with Kweon et al. (2000), gel strength
of sericin increases with decreasing surface tension
and the gelation time decreases with the addition of
high concentrations of poloxamer gel. The reason
behind this is that the hydrophilic parts of latter gel
absorb the water that surrounding sericin.
Isoelectric point. It is referred to the pH at which a
molecule carries no net electrical charge. It is also
dened as the reference concentration of hydrogen
ions, or other ion in which this condition can be
found. Therefore, it has become customary to
dene the isoelectric point in terms of the pH scale.
The isoelectric point of sericin has been reported
between 3.5 and 4.0. It is due to greater amount of
acids amino-acid that basics (Voegeli et al., 1993).
4.2 Methods for sericin extracting
As mentioned above, sericin is removed during
degumming process of silk (Capar et al., 2008).
This procedure is based on the protein hydrolysis
by using chemical, thermal or physical processes
(Gupta et al., 2013). Detergents (Vaithanomsat
& Kitpreechavanich, 2008; Capar et al., 2008),
alkalis, acids and hot water (Sothornvit et al.,
2010; Padamwar & Pawar, 2004; Khan et al.,
2010) can also be used.
Wastewaters from the degumming process can
contribute to increase the deposited organic load in
aqueous efuents, leading to water pollution. This
is due to the solubilized sericin during process,
which increases the BOD and COD (Takasu et al.,
2002; Capar et al., 2008; Mondal et al., 2007). It
has been reported a production of about 1 million
ton of cocoons (fresh weight) worldwide, this
is equivalent to 400.000 ton of dry cocoon, and
50.000 ton of sericin (Zhang, 2002).
Due to the increasing global attention on the
processes of cleaner production, sericin is being
studied as a bioactive compound, which can be

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used in the food, biomedical, pharmaceutical and
cosmetic industries.
Along with the cleaner production, some methods
are being studied about extraction and recovery
of this protein. This last topic includes the use of
alkaline proteolytic enzymes (Freddi et al., 2003),
ltration membranes for recovery (Capar et al.,
2008), and also technologies such as infrared
(Gupta et al., 2013). These new methods bring with
them both positive and negative characteristics.
For example, the use of enzymes requires less
water, energy and chemicals, but it is expensive
and generates the degradation of sericin (Arami
et al., 2007). With respect to infrared technology,
this is associated with cost reduction and higher
efciency in the heating cycle; however, it is still
an expensive technology.
The sericin extraction process in hot water using
both high temperatures and pressures is an example
of an environmentally friendly technology (Zhang,
2002; Padamwar & Pawar, 2004; Sothornvit et al.,
2010). Recovering and using sericin via this
method can represent a signicant economic,
social and environmental benet. This
methodology does not need to use any harmful
solvent (water is sufcient), and therefore protein
recuperation is achieved easily by dehydration
sample. Nevertheless, it must be especially careful
during the process conditions, because they are
associated not only with the extraction yield, but
also with characteristics of the obtained sericin
and the quality of the resulting bre (Aramwit et
al., 2010; Sothornvit et al., 2010).
5. Applications of silk sericin
Recent studies have shown the potential use of
sericin in biomedical, pharmaceutical and food
industries. Cancer drugs, blood thinners, and cell
culture additives, are some examples of developed
products using granules, gels, solutions and lms
of this protein (Table 1). These developments can
be found in countries such as Italy, USA, China,
Austria, Japan and Romania. (Kundu et al., 2008).
Industry Application Reference
Food
Useful for constipation treatment.
Improvement of some minerals (Zn, Mg, Fe and Ca) bio-
availability.
Antioxidant and suppressant of colon tumours.
(Sasaki et al., 2000)
(Sasaki et al., 2000)
(Zhaorigetu et al., 2001)
Cosmetic
Skin care: skin elasticity, anti-wrinkle and anti-aging effect.
Moisturizing and cleansing properties. UV protection effect.
(Ogawa & Yamada, 1999;
Baby & Raj, 2013; Voegeli et
al., 1993; Sasaki et al., 2000)
Nail care: prevents cracks, brittleness, and increases the in-
herent brightness. (Yamada et al., 2001)
Hair care: conditioner, cleansing properties and hair damage
prevention. (Pawar & Padamwar, 2004)
Gel: moisturizing properties. (Kirikawa et al., 2000; Ya-
suda et al., 1998)
Powder: moisture absorption capacity and anti-dermatitis. (Hoppe et al., 1984; Engel &
Hoppe, 1988; Hata, 1987)
Biomedical,
pharmaceutic Cancer prevention, wound healing and drug delivery.
(Zhaorigetu et al., 2001;
Aramwit et al., 2013; Kaew-
korn et al., 2012)
Table 1. Sericin applications.
Source: Adapted from (Kundu et al., 2008).

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Besides keratin, the corneum stratum has a
special humectant mixture known as Natural
Moisturizing Factor (NMF). This factor is
dened as a group of hydrosoluble and/or hy-
drodispersible molecules, which are present in
the intercellular spaces of the stratum. They also
can be found at the skin free surface, as a result
of the physiological processes that occur at skin
level (Fábregas & Del Pozo, 2007).
Wide varieties of moisturizers are available in
the market. They contain wetting agents such as
vegetable glycerine, water, jojoba oil, vitamin
E oil, sorbitol, among other products. In recent
years, wetting properties of sericin have been
evaluated in different cosmetic formulations, such
as creams and lotions (Table 2). It has been found
that a powder mixture of silk broin (70-95%)
and sericin (5-30%) has antistatic characteristics
and capacity to absorb moisture (Kirikawa et al.,
2000); and both detection and UV ltration are
enhanced (Yoshioka et al., 2001). Other cosmetic
applications include sericin powder (Yamada
&Yuri, 1998), and other products that absorb
sweat and grease secreted from the sebaceous
glands of the skin (Miyashita, 1999).
5.1 Cosmetic applications
Sericin's properties such as biocompatibility,
biodegradability and wettability allow the
development of cosmetic products for skin, nails
and hair (Pawar & Padamwar, 2004; Voegeli et
al., 1993; Yamada et al., 2001). Moisturizers have
had a special development; they are mainly used
to prevent and delay the dehydration of the top
layer of the skin. This condition occurs when the
water of the stratum corneum (outermost layer
of the epidermis) is lost faster of what it receives
from the inner layer, and also can be possible due
to a reduction of lipids of the stratum corneum
(GmbH Ziolkowsky, 1998). The dehydration
can be evidenced when skin is brittle and rough,
although water is being constantly supply from
inside the body (Barel et al., 2001).
Normal and healthy skin has a wet, clean, soft,
exible, malleable, and practically wrinkle-free
look (Idson, 1987). The smoothness of the skin is
determined by its content of water, which should
be at least 10% to keep this condition. When water
content lowers this level, keratin, epidermis major
component, becomes less exible (Blank, 1952).
Product Effects Reference
Gels using 1.5% (p/p) and 2.0% (p/p) of seri-
cin, 2.5-10% (p/p) of pluronic acid, and 0.05-
0.20% (p/p) of carbopol.
Prevents water loss from the skin
top layer. Forms a proactive and
moisturizing surface that gives to
the skin a silky, smooth feeling.
(Padamwar et al., 2005)
1% (p/p) sericin and 4% (p/p) D-glucose lotion. Moisturizer. (Yamada et al., 2001)
Creams containing 0.001-30% (p/p) of sericin.
Improves cleaning properties with
less skin irritation. (Sakamoto & Yamakishi, 2000)
Controls skin problems as dermatitis. (Yasuda et al., 1998)
Nail cosmetics with 0.02-20% (p/p) of sericin. Helps to prevent brittleness and
provides shine to the nails. (Yamada et al., 2001)
Hair cosmetics containing sericin between 0.02
to 2% (w/w), and bath preparations with 0.01-1
% (w/w) of fatty acids from olive oil.
Reduces surface hair damage. (Hoppe et al., 1984)
Hydrolysed sericin with low molecular weight. Hair and skin conditioner. (Hata, 1987)
Shampoo with sericin and pelargonic acid. Helps with hair cleaning. (Engel & Hoppe, 1988)
Table 2. Cosmetic products formulations including silk sericin.

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collagen and antimicrobial properties, respectively.
However, they observed that sericin could partially
inhibit the sulfadiazine action, due to the presence
of small areas of microbial inhibition, thus, the
size of the wound did not signicantly chance
(Aramwit et al., 2009). Between 2010 and 2011, a
new investigation conducted in Bangkok showed
for the very rst time that silk sericin could be
successfully used in clinical application for wound
healing. In this work, sericin (8% w/w) was added
to a standard antimicrobial cream of sulfadiazine
that contained zinc (1%). This new formulation
was able to help healing an open wound of second-
degree and preventing an infection without serious
adverse reactions (Aramwit et al., 2013).
Bandage. Development of new wound dressing
materials have been possible due to healing
properties of sericin. Clinical evaluation of a sericin/
PVA scaffold, which was used in patients with skin
grafts, was evaluated. Results showed an accelerated
healing and patient pain reduction, compared to
wounds that were treated with the commercial
bandage Bactigras® (Siritientong et al., 2014).
Tissue engineering. Materials that can be used in
drug delivery, grafts and immobilizing matrices
such as matrices in 2D (lms) and 3D (scaffold)
are one of the mail goals of biomedical research
(Vepari & Kaplan, 2007). Films and scaffold
have been successfully made using a mixture
of gelatine and sericin extracted from silkworm
Antheraea mylitta. Fabricated supports have evenly
distributed pores, good compressive strength and
high swellability. In addition, they show high
porosity, low immunogenicity, and improvement in
both cell attachment and viability. These properties
are critical for tissue engineering and biomedical
applications, which reveals the potential use of
sericin in future development of bio-polymeric
grafts (Mandal et al., 2009).
5.3 Food applications
Today, FDA has included sericin and its derivatives
in the “Generally Recognized as Safe - GRAS”
list (Food and Drug Administration, 2001). The
main characteristic of this protein is its antioxidant
5.2 Medical applications
Sericin has both antioxidant and anticoagulant
properties (Kundu et al., 2008). These characteristics
have led to the development of multiple investigations
in order to apply these in the medical eld. Some
examples include applications in anticarcinogenic
and healing products, and in tissue engineering.
Anticarcinogenic. The antioxidant effect of sericin
can represent a signicant health benet. Studies
have shown that this protein allows a reduction in
the oxidative stress in the human organs such as the
colon; as well as a reduction in the number of cancer
cells. Studies have shown that, the sericin that is
taken orally (by mouth) by rats and mice, helps
to effectively suppress the 1,2-dimethylhydrazine
agent. As this agent is a cancer growth promoter,
a reduction of the incidence of colorectal cancer
was observed when this agent was eliminated
(Zhaorigetu et al., 2001; Kaewkorn et al., 2012).
Additionally, it has been reported that sericin inhibits
the growth of cloned tumor cells and activates
the apoptosis factor, leading to an apoptosis of
cancer cells in rats. Furthermore, sericin that is not
digested by the colon, it has a strong antioxidant
effect, which reduces the oxidative stress and colon
tumorigenesis (Haorigetu et al., 2007).
Healing. Sericin has good hydrophilic properties, it
is also biocompatible and biodegradable, it actives
the collagen production in wounds, and induces
epithelialization (Aramwit et al., 2010; Sangcakul
Aramwit, 2007). It is also reported that sericin promotes
both attachment and proliferation of broblasts and
keratinocytes in the human skin (Aramwit et al.,
2013). These features allow its potential use as a
wound healing agent. Aramwit & Sangcakul (2007)
have made various tests using topical applications of
sericin. They reported that cream with sericin powder
(8% w/w) improvesscarring and reduces wound
size in rats, without causing any allergic reactions
(Aramwit & Sangcakul, 2007).
Aramwit et al. (2009) have worked on developing
a cream of sericin (8% w/w) in combination
with silver sulfadiazine (SSD); the authors took
advantage of these ingredients by promoting the

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function; therefore, it has been proposed a
functional food. However, commercial foods that
contain this protein or any related products are
still not available.
Oxygen is responsible for the production of free-
radicals in the organism. This as a consequence
of physiologic processes that are involved in the
correct functioning of the human body, including
breathing and reactions at cell level (Dasgupta
& Klein, 2014). For this reason, the biological
production of antioxidant compounds is needed,
in order to balance the concentration of the free
radicals. Naturally, the body produces its own
antioxidants, called endogenous (Samaranayaka
& Li-Chan, 2011).
Free radicals are produced inside the body
due not only by physiological processes, but
also by external factors such as environmental
contamination and smoking. This last situation
leads to the overproduction of these radicals,
which cannot be stabilised by the endogenous
antioxidant. As a solution, it is suggested the
intake of exogenous antioxidants in a daily
basis, which help to avoid the oxidative reactions
increase. These reactions are related to human
illness such as cancer, rheumatoid arthritis,
and diabetes (Gigardi et al., 2010), and also to
neurodegenerative diseases such as Alzheimer
and arteriosclerosis (Rizzo et al., 2010).
Additionally, there are evidences that show
some benecial effects of sericin in stabilizing
free- radicals such as hydroxyls, super oxides,
DPPH and ABTS (Chlapanidas et al., 2013;
Dash et al., 2007). Furthermore, sericin has
antioxidant effect during of the linoleic acid
per-oxidation (Fan et al., 2007) and in vitro
lipid peroxidation (Norihisa et al., 1998).
Benecial effects of sericin have been linked to
its proteinic characteristic and other substances
(avonoids, katekins, kercitinas, epicatequins
and carotenoids) present in this protein after
the extraction process (Butkhup et al., 2012;
Chlapanidas et al., 2013). Additionally, sericin
can suppress peroxidation of lipids and inhibit
tyrosinase enzyme activity. This enzyme catalyzes
the tyrosinase oxidation, which is the amino acid
responsible for the skin melanin biosynthesis,
and the enzymatic browning in foods (Norihisa
et al., 1998).
According to Padamwar & Pawar (2004),
sericin has a synergic effect during the intestinal
absorption of minerals such as iron, zinc,
magnesium and calcium. Other laboratory studies
have demonstrated an increase in absorption of
iron (41%), zinc (41%), magnesium (21%) and
calcium (17%) in rodents, after they ingested
this protein (Sasaki et al., 2000). In addition,
there are evidences of favorable effects in the
intestinal health of rodents, as sericin helps to
modular both fermentation and barrier processes
(Okazaki et al., 2011). Due to these properties,
sericin could be used in developing fortied
foods and nutritional supplements.
Furthermore, there are reports related to the
effect of sericin in food products. For instance,
results released by Takechi et al. (2011) showed
the emulsifying effect of sericin when it was
added to salad dressing. These results proved
that high molecular weight protein increases
the emulsion stability up to two days. Also,
there is another report published by the same
authors in 2014, where both palatability and
structure of a bread produced with sericin were
evaluated. The study evidenced a reduction of
the specic volume of the bread, and a darker
color on its crust, without signicant alteration
of its physical properties (Takechi & Takamura,
2014).
Sericin has a high content of bioactive peptides
(PB) that are specic fragments of proteins.
Their amino acid sequence is directly related
to the benecial effects on corporal functions,
specically on systems such as cardiovascular,
nervous, gastrointestinal and immune
(Samaranayaka & Li-Chan, 2011). However,
peptides of sericin have been also studied
with the aim to improve both, the antioxidant
and inhibitor tyrosinase activity, related to an
increased intestinal absorption as consequence
of the size protein reduction (Wu et al., 2008).

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6. Conclusions
Silk sericin is considered a waste of the silkworm
current Colombian industry. Properties such as its
capacity: hydrophilic, antioxidant, antimicrobial,
anticancer and anticoagulant, as well as its UV
protection, biodegradability and cell biocompatibi-
lity, have enabled it to have cosmetic applications
successfully. Sericin presents a potential in the
development of biomedical, pharmaceutical and
food products. In Colombia, there are few studies
addressed to reuse waste generated in the silkworm
industry, leaving a signicant gap in the science.
For this reason, it is important to investigate about
new ways to obtain high added value products, in
order to generate a potential environmental, social
and economic benet to farming families.
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