Cell culture and cryopreservation are necessary for clinical therapy and cells storage. The addition of 10% (v/v) foetal bovine serum (FBS) to basal culture media has been common practice and is one of the most widely used methods. FBS media added with 10% DMSO (dimethyl sulfoxide) have also been used for cryopreservation cells. Ideally, FBS should be avoided because of high cost and bio-safety. Silk sericin has been used as a serum substitute and an additive due to its good hydrophilicity and biological safety. This article summarizes a few details about the processing of sericin and its application as a serum substitute or an additive for cell culture and cryopreservation media. Sericin can be a potential novel serum substitute or an additive for cell culture and cryopreservation media.

In this experiment, the morusin separated from the branch bark of cultivated mulberry, an edible medicinal plant, is used to study the inhibition of morusin in the human hepatocellular carcinoma cell line Bel-7402. The control and morusin-treated groups were used to study the effects of morusin on cell proliferation, apoptosis, antioxidant level and expression of tumor-associated genes. The results indicated that Bel-7402 cell activities were inhibited significantly after treatment with 50 μg mL−1 and 100 μg mL−1 morusin for 24 h, exhibiting a significant difference compared with the control group. Additionally, the symptoms of apoptotic cells, such as cell shrinkage and the reduced number of cells, were observed using an inverted microscope. Flow cytometry analysis indicated that the apoptotic rates of the tumor cells were 19.86%, 68.20% and 81.00%, respectively, after treatment with different concentrations of morusin for 24 h, and the mitochondrial membrane potentials were also decreased with the increase in morusin concentration. In addition, morusin can also induce the increase in antioxidant activity of the cells. It was also demonstrated that morusin can both downregulate the expression of NF-κB and upregulate caspase-3 and caspase-9. Western blotting results indicated that morusin can increase the expression of P-ERK1/2 and P-JNK to induce cell apoptosis through the MAPK pathway. Furthermore, morusin can induce the upregulation of the expression of Beclin-1, P53 and the downregulation of NF-κBp65. Therefore, the anti-tumor effect of morusin can induce the apoptosis of human hepatoma Bel-7402 cells via the mitochondrial and MAPK pathways.

•Water-soluble extract of S. stolonifera has anti-tumor effects on Lewis mice.•Main bioactive components from S. stolonifera were identified and quantified.•Gene p53, Sox, Bax, Bcl2 were altered after treated with S. stolonifera.Saxifraga stolonifera is an evergreen and herbaceous plant well known in Korea, Japan and western China, which has great potential applications in gardening and pharmacology. The aim of this study is to evaluate the anti-tumor effects of S. stolonifera extraction on lung tumors of Lewis mice. By the measurement of MS/MS, we found that there were four main bioactive components in methanol extract of S. stolonifera, including gallic acid, norbergenin, protocatechuic acid and bergenin, and the results of quantitative analysis showed that the contents of gallic acid, protocatechuic acid and bergenin in methanol extract of S. stolonifera were 5.150, 1.492, 24.559 mg/g, respectively. Animal experiment showed that the mean tumor weight of Lewis lung carcinoma-bearing mice treated with water-soluble extract of S. stolonifera was obviously smaller than model group (cis-DDP), and its inhibition rate was 49.2%. In addition, histopathological evaluation and immunohistochemical assay confirmed the anti-tumor effects of S. stolonifera. Investigation of four haematological parameters revealed that the Lewis mice fed with S. stolonifera showed good resilience in the level of leukocyte, haemoglobin, blood platelets and red blood cell compared with the model group. In addition, RT-PCR suggested that the relative expression of pro-apoptosis gene p53, Sox and Bax was enhanced, while the relative expression of anti-apoptosis gene Bcl2 was diminished in comparison with model group. These results suggested that water-soluble extract of S. stolonifera has anti-tumor effects on Lewis lung tumors.

•Bombyx mori silk is composed of fibroin, sericin and non-sericin component.•The extraction and recovery methods of sericin are reported.•The composition, properties and biological activity of sericin are described.•A potential application of sericin in sustainable development is also presented.Bombyx mori silk is composed of 60–80% fibroin, 15–35% sericin and 1–5% non-sericin component including wax, pigments, sugars and other impurities. For two decades, the protein-based silk fibroin was extensively used in the research and development of medical biomaterials and biomedicines. Sericin is frequently ignored and abandoned as a byproduct or waste in the processing of traditional silk fabrics, silk floss or modern silk biomaterials. However, similar to fibroin, sericin is not only a highly useful biological material, but also a lot of biological activity. Moreover, the non-sericin component present with sericin in the cocoon shell also has a strong biological activity. In this review, the extraction and recovery methods of sericin and the non-sericin component from the cocoon layer are reported, and their composition, properties and biological activity are described to produce a comprehensive report on biomedical materials and biological drugs. In addition, related problems or concerns present in the research and development of sericin are discussed, and a potential application of sericin in sustainable development is also presented.

•Novel N,O-carboxymethyl chitosan from silkworm pupa•Prevention of postoperative intestinal adhesion•A lower level of TGF-β1 expressionN,O-Carboxymethyl chitosan (NOCC) can prevent postsurgical adhesion formation. Here, we described the preparation of a novel silkworm pupa NOCC and its effects on the prevention of postoperative adhesion in a rat cecal abrasion model. The degree of deacetylation (DDA) of silkworm pupa chitosan was only 49.87 ± 0.86%; regardless, it was used as the raw material to construct the novel silkworm pupa NOCC, which had a weaker crystallinity than the NOCC standard. Sixty male Sprague–Dawley rats were divided into three groups and treated as follows: 0.9% normal saline solution as a negative control, medical anti-adhesion gel as a positive control and the silkworm pupa NOCC anti-adhesion solution. Two and three weeks after surgery, the animals were killed and the adhesion formation was scored. The silkworm pupa NOCC solution significantly decreased the levels of WBC, TNF-α, IL-1β, IL-2, IL-6 and IL-8 but had no effect on IL-4. Additionally, a lower level of TGF-β1 expression was found in the silkworm pupa NOCC group, and significantly less collagen (P < 0.01) and fewer inflammatory cells and fibroblasts were detected in the animals of this group. These results suggested that the novel NOCC from silkworm pupa using the method described here have potential applications in the prevention of postoperative intestinal adhesion.

Exposure of the skin to ultraviolet B radiation causes oxidative stress that results in sunburn, photoaging, and skin cancer. We aimed to investigate the antioxidant, anti-inflammatory, and anticancer effects of a flavonoid extract (FE) from the sericin layer of Daizo silkworm cocoons. The analytical HPLC results showed that the FE of the Daizo cocoon shell contains the flavonoid aglycones quercetin (21.76 ± 0.66 g kg−1 FE) and kaempferol (4.62 ± 0.11 g kg−1 FE). In a skin tumour mouse model, the topical application of FE reduced the number of tumours per mouse from 5.1 in the model group to 3.2 and 2.6 in two sample groups (3 mg and 5 mg FE) prior to induction with UVB/DMBA. Our in vivo experimental results also showed that the FE could reduce the phototoxicity of UVB at different cellular and molecular levels by decreasing the severity of dermal inflammation and keratinocyte proliferation through the modulation of oxidative stress and NF-κB. FE could increase antioxidase activity and decrease the levels of the inflammatory cytokines IL6 and TNF-α. These results suggest that the flavonoid extract mainly consisting of flavonoid aglycones might be a potential candidate for anti-cancer drugs in the prevention and treatment of skin cancer. This study has profound significance for the comprehensive utilization of silkworm cocoon.

•In this article, powdered micro- and nanofibers were obtained by ultrasonication.•The ultrasonication method which we introduce is simple, efficient and industrial.•The diameter of the powdered microfibers was approximately 5–10 μm.•The diameter of the powdered nanofibers was approximately 30–120 nm.•The ε-amino group content of the powdered-fibers increased significantly.Silk derived from Bombyx mori silkworm cocoons was degummed in an aqueous sodium carbonate solution, and the resulting silk fibroin fibers were placed in an acidic aqueous solution and were treated with ultrasonication to obtain powdered micro- and nanofibers. The morphologies and spectral characteristics of these powdered silk fibers were investigated in detail. The shape, surface and structural features of the powdered fibers were affected by the ultrasonic power and media. Increasing the acidity of the ultrasonic solution and increasing the ultrasonic power increased the fiber breakage speed, resulting in shorter fiber lengths. Powdered microfibers could not be obtained in a formic acid solution, while powdered nanofibers whose diameter below 1 μm were obtained in a combined formic acid and hydrochloric acid ultrasonication solution. Observation via SEM and optical microscopy revealed that the microfiber diameters were approximately 5–10 μm, and those of the nanofibers were approximately 30–120 nm. The analysis of laser sizer showed that the microfiber sizes ranged mainly from 20 to 100 μm. FT-IR and XRD spectra demonstrated that the relative amount of β-sheets increased after the ultrasonic treatment. The ε-amino group content on the surface of the micro- and nanofibers increased significantly. These studies provide reliable methods for the preparation of nano-scale silk fibroin fibers by ultrasonication and open new avenues for the development of powdered silk fibers as advanced functional biomaterials.

•The SPS first used as a silk degumming agent in this study is an amino acid-type anionic surfactant that was synthesized using silk fibroin amino acids and lauroyl chloride.•We studied it systematically in comparison to the traditional degumming methods such as sodium carbonate (Na2CO3) and neutral soap (NS).•The experimental results showed that the sericin can be completely removed from the silk fibroin fiber after boiling the fibers three times for 30 min and using a bath ratio of 1:80 (g/mL) and a concentration of 0.2% SPS in an aqueous solution.•The results of the tensile properties, thermal analysis, and SEM all show that SPS is similar to the NS, far superior to Na2CO3. In short, SPS may be used as an environmentally friendly silk degumming agent in the silk textile industry and in the manufacture of silk floss quilts.The silk protein surfactant (SPS) first used as a silk degumming agent in this study is an amino acid-type anionic surfactant that was synthesized using silk fibroin amino acids and lauroyl chloride. We studied it systematically in comparison with the traditional degumming methods such as sodium carbonate (Na2CO3) and neutral soap (NS). The experimental results showed that the sericin can be completely removed from the silk fibroin fiber after boiling the fibers three times for 30 min and using a bath ratio of 1:80 (g/mL) and a concentration of 0.2% SPS in an aqueous solution. The results of the tensile properties, thermal analysis, and SEM all show that SPS is similar to the NS, far superior to Na2CO3. In short, SPS may be used as an environmentally friendly silk degumming/refining agent in the silk textile industry and in the manufacture of silk floss quilts.The silk protein surfactant (SPS) is an amino acid-type anionic surfactant that was synthesized using silk fibroin amino acid and lauroyl chloride. It can be used as a silk degumming agent and it is environmentally friendly.

For ultrathin metallic films, either supported or free-standing, the inside nanocrystalline nature significantly reduces the electron and thermal transport. Quantum mechanical reflection of electrons at the grain boundary reduces the electrical conductivity further than the thermal conductivity, leading to a Lorenz number in the order of 7.0 × 10–8 W Ω K–2, much higher than that of the bulk counterpart. We report on a finding that for ultrathin (0.6–6.3 nm) iridium films coated on degummed silkworm silk fibroin, the electron transport is around 100–200% higher than that of the same film on glass fiber, even though the grain size of Ir film on silkworm silk is smaller than that on glass fiber. At the same time, the thermal conductivity of the Ir film is smaller or close to that of the film on glass fiber. Its Lorenz number is found close to that of bulk crystalline Ir despite the nanocrystalline structure in the Ir films. This is similar to the behavior of metallic glasses. Our study of gold films on silkworm silk reveals the same trend of change as compared to that on glass fiber. Electron hopping and tunneling in silkworm silk is speculated to be responsible for the observed electron transport. The finding points out that silk could provide a better substrate for flexible electronics with significantly faster electron transport.Keywords: electron transport; gold film; iridium film; Lorenz number; silkworm silk; thermal conductivity

•Five caffeoyl compounds were identified from purple sweet potato Ipomoea batatas.•Two caffeoyl compounds were found for the first time.•These antioxidation activities were related to the number of caffeoyl group.More than 10 red anthocyanins and related glucosides have been isolated and identified from purple sweet potato (Ipomoea batatas, Ayamurasaki) in the recent decades. This paper reports the isolation of colourless caffeoyl compounds from purple sweet potato using AB-8 macroresin absorption and semi-preparative HPLC-DAD. The structures of the five isolated monomers were identified as: 5-caffeoylquinic acid (1), 6-O-caffeoyl-β-d-fructofuranosyl-(2-1)-α-d-glucopyranoside (2) and trans-4,5-dicaffeoylquinic acid (3), 3,5-dicaffeoylquinic acid (4), 4,5-dicaffeoylquinic acid (5), and by ESI/MS and NMR. Compounds 1, 4 and 5 were reported previously in combination with anthocyanins in purple sweet potato, whereas 2 and 3 were found for the first time. In vitro antioxidant assay showed trans-4,5-dicaffeoylquinic acid has significant antioxidant activities. These results should lay the groundwork for further work identifying purple sweet potato as a healthy food.

The objective of this study was to improve silk floss processing technology. Silkworm (Bombyx mori) cocoons were quickly reeled into a raw silk sheet with cycling of hot alkaline eluent in a processing machine. The raw silk sheet was refined in the strongly alkaline electrolyzed water (SAEW) for 0.5 h, and the silk floss (degummed silk fiber equivalent to ∼40% (w/w) of the whole cocoons) was obtained as a raw material for the manufacture of silk fabrics such as silk quilts. The alkaline eluent and the refining solution were separated by an ultrafilter, the filtrate contained the sericin oligomeric peptides and free amino acids (SAA) with a low molecular mass, and the retentate was a sericin polypeptide (SP) with a range of high molecular mass values; the filtrate was again separated by the nanofiltration, obtaining the retentate contained SAA, while the filtrate became the pure water that can be recycled as the alkaline eluent; the SAA in the retentate was concentrated to about 20% (w/v) by using rotary evaporation; the finally obtained SAA was used for the synthesis of a lauroyl sericin-based surfactant (LSBS) with a yield of ∼75%. There was no clear difference between the amino acid compositions of SAA and LSBS. The surface tension and critical micelle concentration (CMC) of LSBS was much lower than that in the SAA, and LSBS had high foaming power. The emulsifying power of SAA and LSBS in an oil–water (O–W) phase with the ethyl acetate as the oil phase was better than that with the benzene. Generally, the LSBS displayed good surface properties. A novel technology in the present work was developed for the silk floss industry, facilitating efficient recovery and use of sericin as well as the recycling of water and reducing the serious environmental pollution resulting from the strongly alkaline waste that contains the sericin released from the traditional procedure.

Silk fibroin derived from Bombyx mori is a biomacromolecular protein with excellent biocompatibility. The aim of this work was to develop silk fibroin nanoparticles (SFNs) derived from the fibrous protein, which is a novel vector for enzyme modification in food processing. Silk fibroin was dissolved in highly concentrated CaCl2 and subjected to lengthy desalting in water. The resulting liquid silk, which contained water-soluble polypeptides with molecular mass ranging from 10 to 200 kDa, and β-glucosidase were added rapidly into acetone. The β-glucosidase molecules were embedded into silk fibroin nanoparticles, forming β-glucosidase–silk fibroin nanoparticles (βG–SFNs) with a diameter of 50–150 nm. The enzyme activity of the βG–SFN bioconjugates was determined with p-nitrophenyl-β-d-glucoside as the substrate, and the optimum conditions for the preparation of βG–SFNs were investigated. The enzyme activity recovery of βG–SFNs was 59.2 % compared to the free enzyme (specific activity was 1 U mg-1). The kinetic parameters of the βG–SFNs and the free β-glucosidase were the same. The βG–SFNs had good operational stability and could be used repeatedly. These results confirmed that silk protein nanoparticles were good carriers as bioconjugates for the modification of enzymes with potential value for research and development. The method used in this study has potential applications in food processing and the production of flavour agents.

Silk derived from cocoons of the female silkworm (Bombyx mori) was made into three kinds of test material, degummed fiber, liquid fibroin and regenerated silk fibroin membrane (RSFM). The effect of the silk degumming and fiber dissolution system (SD–FDS) on the molecular structure and properties of silk fibroin were studied in detail. Degumming with Na2CO3 solution had the greatest impact on silk fibroin fiber, resulting in significant reduction of the thermal stability and crystallinity, and the fiber tensile property was only half of that degummed with urea buffer. The moderate degumming solution was urea buffer, followed by strongly alkaline electrolyzed water (SAEW). SDS-PAGE showed that the silk fibroin degummed with 8.0 M urea at 80 °C and dissolved in 9.3 M LiBr at 25 °C was similar to the natural silk fibroin in vivo, but boiling in Na2CO3 solution leads to serious breakage of the silk fibroin peptide chain. The degree of breakage of the peptide chain is positively correlated with the storage time of liquid silk fibroin. DSC showed the more nearly intact the silk fibroin peptide chain, the higher the thermal decomposition temperature. The regenerated condition of the silk protein is often overlooked during the research process, while our study showed that different silk degumming and fiber dissolution systems will have different influences. The results of this test help us gain a deeper understanding of the effect of silk degumming and fiber dissolution on the molecular structure and properties of silk fibroin and provide important experimental data for screening and using silk protein as advanced functional biomaterials, such as medical tissue engineering materials.

The cocoon shell of the silkworm Bombyx mori consists of silk fibroin fiber (70%) surrounded by a sericin layer made up of sericin (25%) and non-sericin (5%) components. The non-sericin component which consists of carbohydrate, salt, wax, flavonoids and derivatives is often overlooked in applied research into sericin and its hydrolysate. Here, sericin and non-sericin compounds were obtained from the sericin layer of five types of cocoon shell by means of degumming in water followed by extraction and separation in ethanol. These ethanol extracts were found to mainly contain flavonoids and free amino acids possessing scavenging activities of the 2,2-diphenyl -1-picrylhydrazyl (DPPH) free radical and inhibiting activities of tyrosinase, which were much greater than the corresponding activities of the purified sericin proteins. The extracts also strongly inhibited α-glucosidase while the sericins had no such activity. In particular, the inhibitory activities of the ethanol extract of Daizo cocoons were much greater than those of the other cocoons. The IC50 values of the Daizo cocoons for DPPH free radicals, tyrosinase, and α-glucosidase were 170, 27, and 110 μg mL−1, respectively. The bioactivities of the non-sericin component were much higher than the activity of sericin alone. In addition, the in vivo test showed preliminarily that the administration of the non-sericin component had effectively resistant activity against streptozocin (STZ) oxidation and that of the purified sericin could also evidently decrease the induction ratio of diabetic mice induced by STZ. Therefore, ethanol extract protocols of the sericin layer of cocoon shells provide a novel stock which, together with sericin protein, has potential uses in functional food, biotechnological and medical applications.

Silk fibroin (SF) when dissolved in highly concentrated CaCl2 solution formed a series of degraded polypeptides with a molecular mass range of 10–70 kDa. After the liquid silk, mixed mildly with L-asparaginase (ASNase), was introduced rapidly into excess acetone, the enzyme not only was not inactivated but was also well immobilized in simultaneously formed silk fibroin nanoparticles (SFNs). The resulting SFN–ASNase bioconjugates were easily isolated from acetone solution by centrifugation. The bioconjugates were crystalline globular particles of 50–120 nm in diameter, with high enzyme activity and showed similar enzymatic kinetics such as pH, reactive temperature, thermostability in solution and Michaelis constant to the native form. The bioconjugates could resist a high temperature of 90 °C in dry conditions for 30 min, and had a high recovery (90%), a greatly increased resistance to trypsin digestion, and better stability in serum, and storage stability in solution. No leakage of the enzyme from the nanoparticles occurred. These results indicated that ASNase was uniquely and efficiently bioconjugated in the protein nanoparticles that possessed a fine crystallinity. Thus, the highly efficient processing technology and use of silk nanoparticles as a novel drug delivery system has potential in research and development.

Bombyx mori silk fibroin is a protein-based macromolecular biopolymer with remarkable biocompatibility. Silk fiber was degummed and subjected to a series of treatments, including dissolution and dialysis, to yield an aqueous solution of silk fibroin, which was introduced rapidly into excess acetone to produce crystalline silk fibroin nanoparticles (SFNs). The SFNs were conjugated covalently with a neutral protease (NP) using glutaraldehyde as the cross-linking reagent. The objective of this study was to determine the optimal conditions for biosynthesis of the SFN-NP bioconjugates. First, SFN-NP was obtained by covalent cross-linking of SFN and NP at an SFN/NP ratio of 5–8 mg:1 IU with 0.75% glutaraldehyde for 6 h at 25 °C. When adding 50 IU of the enzyme, the residual activity of biological conjugates was increased to 31.45%. Studies on the enzyme activity of SFN-NP and its kinetics showed that the stability of SFN-NP bioconjugates was greater than that of the free enzyme, the optimum reactive temperature range was increased by 5–10 °C, and the optimum pH value range was increased to 6.5–8.0. Furthermore, the thermal stability was improved to some extent. A controlled hydrolysis test using the poorly water-soluble protein sericin as a substrate and SFN-NP as the enzyme showed that the longer the reaction time (within 1 h), the smaller the molecular mass (<30 kDa) is of the sericin peptide produced. The SFN-NP bioconjugate is easily recovered by centrifugation and can be used repeatedly. The highly efficient processing technology and the use of SFN as a novel vector for a protease has great potential for research and the development of food processing.

•A novel chitosan hydrogel membrance (CHM) was formed on a naoporous barrier film at 60VDC.•The trsnsparent CHM had an irregular net structure.•CHM had good strength, malleability and swelling index.•CHM did not incite serious inflammatory reactions in vivo.Here, we report a novel chitosan hydrogel membrane (CHM) created by an improved electrophoretic deposition. Unlike a traditional CHM by electrophoretic deposition, the CHM was formed on a nanoporous film as a barrier using a homemade device at a high DC voltage (60 VDC). The CHM maximum recovery of 81.7% could be achieved after 1 h of electrophoretic deposition. The transparent CHM with an elongation of 42.46% and swelling index of 538.86% was a mixture of type I and type II crystal structures. SEM revealed that the CHM had an irregular net structure. The CHM was sufficient for L-929 mouse fibroblast cell adhesion and growth. To demonstrate immunocompatibility with host tissues, H&E and TGF-β1 were observed and the expressions of TNF-α and NF-κB were measured up to 3 weeks post-implantation. Although these scaffolds demonstrated an initial pro-inflammatory response, the amount of inflammatory cells and the expressions of TGF-β1 returned to baseline control values at 3 weeks. The expressions of TNF-α and NF-κB had no significant difference between the experimental and control groups. Animal experiments showed that the CHM did not incite serious inflammatory reactions. Thus, the CHM is a promising medical biomaterial candidate for loading appropriate cells for use as artificial skin or in transplantation.A novel chitosan hydrogel membrane can be formed on a nanoporous film as a barrier at a high 60 DC voltage by an improved electrophoretic deposition.

Alkyl polyglycoside (APG), a nonionic surfactant, is often considered to be a green surfactant and is synthesized using glucose and long chain fatty alcohols. It is used as a degumming agent of Bombyx mori silk fibre in this study for the first time. We studied APG systematically in comparison to the traditional degumming methods, such as aqueous solutions of sodium carbonate (Na2CO3) and neutral soap (NS). After repeatedly boiling silk fibres in an aqueous solution of 0.25% APG three times for 30 min and using a bath ratio of 1:90–120 (g/mL), sericin was completely removed from the fibre. SDS-PAGE showed that the degumming in APG did not induce an evident breakage of the silk fibroin peptide chains, including the light chain and P25 protein. The tensile properties, thermal analysis, and scanning electron microscopic (SEM) observation of the degummed fibroin fibre all show that APG is a degumming agent similar to NS and far superior to Na2CO3. These results indicate that APG is an environment-friendly silk degumming/refining agent in the silk textile industry and in the manufacture of silk floss quilts.APG has potential uses as a green degumming/refining reagent for silkworm cocoons or silk fibres in the silk industry and for sericulture production.

•A novel procedure for refining crude raw silk sheet was developed.•All the sericin from the scouring waste is recovered by ultra- and nanofiltration.•Three clean products of the sericin are obtained by controlled hydrolysis with papain.This study was designed to improve the traditional scouring procedure using a solution of sodium silicate, sodium carbonate, H2O2, surfactant etc. as a refining agent for degumming machine-drawn raw silk sheet (RSS) and raw silk from the cocoon shell of the silkworm Bombyx mori. The RSS was scoured firstly in strongly alkaline electrolyzed water (SAEW, pH ≥ 11.5) consisting mainly of hydroxyl ions by boiling for 30 min and then treated by the traditional scouring procedure (without alkaline compounds), resulting in refined silk floss. The recycled SAEW containing sericin was separated by ultrafiltration into a retentate with a range of high molecular mass values accounting for 10% (w/w) of the cocoon shell and the filtrate was separated by nanofiltration into a purified H2O filtrate and a retentate containing oligopeptides and free amino acids, which can be used directly as food additives or in biological growth media. The ultrafiltration retentate was hydrolyzed by papain under three different conditions into three groups of sericin peptides with high, middle or low molecular mass. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and gel permeation high-performance liquid chromatography (GP-HPLC) showed the molecular mass of these sericin peptides was in the range 0.2–60, 0.2–30 and 0.2–15 kDa. These clean products have a variety of applications, including coating materials for surface modification, cell culture media and food additives. The procedure described here could be applied to the manufacture of silk floss quilts and the process of refining raw silk, which results in three clean products of the silk protein fibroin (i.e. stripped of sericin) and reduces environmental pollution from scouring waste containing sericin.Download full-size image