• International Journal of Industrial Entomology and Biomaterials
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• v.38 no.2
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• pp.51-55
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• 2019

The structure and properties of silk polymers (fibroin and sericin) can be satisfactorily controlled by choosing a suitable silkworm variety and, hence, this parameter (i.e., silkworm variety) has attracted increasing attention. A previous study reported that the crystallinity of white colored silkworm cocoons depends on the silkworm variety. In the present study, sixteen yellow colored silkworm variety cocoons were produced and their molecular conformation and crystallinity were investigated. The conformation of the silkworm cocoons varied with the silkworm variety. Most cocoons exhibited ${\beta}$-sheet conformation, although random coil and ${\beta}$-sheet conformations co-existed in some cocoons (e.g., 21 and D90). The crystallinity of the silkworm cocoons varied with the silkworm variety and the measurement position of the cocoon (i.e., outer surface or inner surface). However, the difference in the crystallinity indices of the outer and inner surfaces comprising the cocoons varied with the silkworm variety, but was <2% for all cocoons, except for MAL.

• International Journal of Industrial Entomology and Biomaterials
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• v.19 no.2
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• pp.265-268
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• 2009

Wild silkmoths can be utilised sustainably in the production of silk as an income for resource-poor rural communities. However, attack by parasitoids and predators affect the quality of cocoons and quantity of raw silk produced. A laboratory experiment was undertaken to quantify the effect of parasitoids' (dipteran and hymenopteran) and predators' (ants) exit and ingress holes, respectively, on silk production. The mean number of shells required to produce fifty grams of raw silk was highest with cocoons parasitised by a dipteran and lowest with unattacked cocoons (but with moths already emerged). Degumming loss was highest in parasitised and lowest in unttacked cocoons, but both were not different from cocoons predated by ants. Shell weight was highest in unattacked cocoons, followed by hymenopteran-parasitised and predated cocoons, with the dipteran parasitized ones being the least. Single cocoon weight was greater in hymenopteran-parasitised and predated cocoons than the dipteran-parasitised and unattacked cocoons. Shell ratio or raw silk, floss and yarn weights were higher in unattacked than parasitised and predated cocoons. The total loss in raw silk attributable to attack by parasitoids and predators ranged between 17.4~31.2%. The results offer baseline information for assessment of economic losses in wild silk farming due to parasitoids and predators in the field.

• Journal of Sericultural and Entomological Science
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• v.13 no.1
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• pp.61-67
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• 1971

This experiment was conducted to know the effects of abnormal cocoons on the silk quality during the silk reeling process. The results obtained are summarized as follows: 1. The length, the width, the weight, the layer weight, and the layer ratio of abnormal cocoons are in every case 0.83∼4.65% less than those of normal cocoons. 2. The thickness of the abnormal cocoon layer is at)out 20.62∼22.4% less than that of the normal cocoon. 3. The sericin solubility of tile abnormal cocoon layer is about 11.75∼30% more than that of the normal cocoon layer. 4. The degumming ratio of the abnormal cocoon layer is about 6.51∼9.32% more than that of the normal cocoon layer. 5. The length of a have, the weight of a tave and percentage of raw silk yield of the abnormal cocoon are decreased 9.43%, 8.53% and 6.72% each as compared with those of the normal cocoon. 6. The percentage of reelability of abnormal cocoons is decreased 9.58％ as compared with that of normal cocoons. 7. The neatness of abnormal cocoons is 3 per cent lower than that of normal cocoons. 8. In the cleanness test of abnormal cocoons, the number of split ends i9 about 1.5∼3.8 times as much as that of normal cocoons. Especially cleanness of abnormal cocoons is 16,3 per cent lower than that of normal cocoons. 9. The number of non-reelable cocoons of abnormal cocoons is increased 1.4∼5.5 times as much as that of normal cocoons. In abnormal cocoon, the number of knot which resulted in the breaking of silk end is increased 1.9∼3.5 times as much as that in normal cocoon.

• Journal of Sericultural and Entomological Science
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• v.18 no.2
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• pp.107-110
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• 1976

In silk reeling process the carry-over cocoons must be submerged in the reeling baths filled with reeling water and left until reopening the operation. Under the detention the carry-over cocoons are apt to decay without any antiseptic treatment. Thus an useful antiseptic for the cocoons is urgently needed, and various antseptic agents have been tested for their applicability to the process. However, such an useful agent has not been developed yet. Formalin has been the only chemical used for antisepticizing carry-over cocoons, although it has many defects as the antiseptic for the cocoons. In these circumstances, recently we newly prepared an antiseptic useful for preventing the carryover cocoons from decaying. We named the new antiseptic preparation "Swi-Se-Yo." The Korean term "Swi-Se-Yo" literally means "please take a rest". Through a series of experiments with Swi-Se-Yo we obtained the following results: 1) Swi-Se-Yo, in 0.05% aqueous solution, exerted a good antiseptic effect on the boiled Cocoons submerged in the reeling baths and the effect lasted for 45 hours. The duration of the effect is about two times longer than that of Formalin. 2) The percentage of cocoon reel ability of the carry-over cocoons treated with Swi-Se-Yo was 6% higher than that of Formalin and was equal to that of flowing cold water. 3) The percentage of raw silk yield of the carry-over cocoons treated with Swi-Se-Yo was almost equal to that of Formalin and to that of flowing cold water. 4) The quality of raw silk of the carry-over cocoons treated with Swi-Se-Yo is the same as that of flowing cold water. Besides the above favourable results, Swi-Se-Yo has many advantages as an antiseptic. Chemically it is very stable. Its antimicrobial action is very strong and the spectrum is very broad. It can be available in water-soluble powder and in small bulk. And it is not harmful to human and domestic animals. Considering these profitable properties of Swi-Se-Yo, it will have a good reputation as a carry-over cocoon antiseptic. (The chemical composition and manufacturing method of Swi-Se-Yo will be published in the near future.)

• Journal of Sericultural and Entomological Science
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• v.17 no.1
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• pp.1-26
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• 1975

These studies were attempted to find out the optimum silk reeling system by use of automatic silk reeling machine to increase raw silk yield and reeling efficiency with various silk reelable cocoons. The obtained results are as follows; 1. The mean silk reelability ratio(X)of the Korean cocoons during the last ten years was 61 per cent, beside 64.7 per cent in autumn cocoon and 57.3 per cent in spring cocoon. However, the ratio variation of autumn cocoons was larger than that of spring cocoons. 2. A positive correlation between cocoon filament breaks during its process and silk reelability levels was shown to be significant. The cocoons of both poor and good reelability evidenced "J" shape distribution on the filament break graph by the order of reeling cocoon end. Many bave breaks were found at the inner shell of the cocoons, or in case of poor reelability cocoons. 3. The morphology of broken cocoon ends during the process was classified into A, B, C, D, E and F types, The occurrence of B type was majority, but that of F type was minority among them. 4. In case of the cocoon cooking, H-type ion-exchanged soft water was better for good reelability cocoons, Na and H-type ion exchanged neutral soft water for those of fair reelability, and alkaline (Na-type) soft water for those of poor reelability, respectively. 5. The modification of cooking water by mixing the above different types of water (50％ Na-type and 50％ H-type passed by standard natural water; 75％ Na-type and 25％ H-type passed by hard natural water; 25％ Na-type and 75％ H-type passed by soluble natural water) made higher yield of raw silk with tess breaks of thread. 6, In case cocoon ends groping water included sodium hexametaphosphate as much as 800 ppm. the groping efficiency and raw silk yield of cocoon was improved. The effect was pronounced in case of poor reelability cordons. 7. The most reasonable cocoon cooking and silk reeling condition for automatic silk reeling process were observed to be rather incomplete cook with good reelability cocoons and optimum cook with poor reelability cocoons succeeded by the reeling bath temperature of 45$^{\circ}C$, 8. The reasonable silk reeling velocities were observed to be about 150m per min. for good reelability cocoons, 120m per min. for fair reelability ones and 90 to 120m per min. for poor reelability ones. 9. In order to improve the raw silk yield of cocoons and reeling efficiency, the cocoon stand-by-ratio for reeling should be kept at the level of 40 per cent for good reelability cocoons or at 60 per cent for poor reelability ones beside necessary end found cocoon condition.

• International Journal of Industrial Entomology and Biomaterials
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• v.44 no.1
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• pp.4-11
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• 2022

In this study, cocoons from different silkworm strains and rearing seasons were collected and immersed in water at elevated temperatures to investigate the effect of a wet treatment on their morphology and crystallinity. Untreated cocoons exhibited different crystallinities depending on the silkworm strain and rearing season; however, no distinct changes in their morphological structure were observed. Furthermore, after wet treatment, the differences in the crystallinities of cocoons disappeared. In addition, wet treatment of degummed silk (i.e., fibroin) did not change its crystallinity. These results indicate that different crystallinities of the untreated cocoons collected from various silkworm strains and rearing seasons are due to the different characteristics of sericin in the cocoons.

• International Journal of Industrial Entomology and Biomaterials
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• v.35 no.2
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• pp.71-76
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• 2017

The cocoon's color of silkworm, Bombyx mori L. is usually white. But some are yellow, flesh and green colors because of modified characteristics. The yellow and flesh cocoons depend on carotenoid pigments, green cocoons are determined by flavonoid pigments. The cocoon's color is affected by the genes controlling penetration process from midgut to coelom and silk gland. Y (Yellow blood, 2-25.6) and I (Yellow-inhibitor, 9-16.2) genes are involved in the penetration process of carotenoid pigments from midgut to coelom, C (Outer-layer yellow cocoon, 12-7.2) and F (Flesh, 6-13.6) genes from coelom to silk gland. Therefore, the carotenoid cocoon's color depends on the genotype Y, I, C and F genes and their combination. Among them, C gene is sympathetic gene, which are known as C, CI and CD. C (Outer-layer yellow cocoon) genes make yellow cocoons on outer-layer and white cocoons on inter-layer, and CI (Inner-layer yellow cocoon) genes do yellow cocoons on inter-layer and dilute yellow cocoons on outer-layer. CD gene is known as making dilute yellow cocoons all layer. In this study, we have checked the dominance relation of C sympathetic genes among carotenoid genes for color cocoons by using strains related to the genes for color cocoons and investigated the aspect that pigments were penetrated in silk gland by action of each gene.

• International Journal of Industrial Entomology and Biomaterials
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• v.46 no.1
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• pp.9-15
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• 2023

Recently, a silkworm strain (tentatively named Sericinjam) producing 100% sericin cocoons has been studied in South Korea. In this preliminary study, the crystallinity, mechanical properties, and dissolution conditions of sericin from Sericinjam cocoons were examined. The Sericinjam cocoon could be dissolved in water at high temperature (120℃) and high pressure (HTHP method) in an autoclave and in a CaCl₂/H₂O/EtOH mixture (ternary solvent method), resulting in 82% and 97% dissolution after 30 min, respectively. The solution viscosity of the silk sericin formic acid (SSFA) solution obtained from sericin extracted using the ternary solvent method was higher than that obtained using the HTHP method; however, SSFA solutions obtained from sericin extracted from conventional Baekokjam cocoons yielded a higher solution viscosity. The crystallinity and breaking strength of the sericin film from Sericinjam cocoons were slightly lower, respectively, than those from Baekokjam cocoons. In contrast, the elongation at break of the Sericinjam sericin film obtained using the HTHP method was higher than that of the Baekokjam sericin film.

• Journal of Sericultural and Entomological Science
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• v.51 no.2
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• pp.142-146
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• 2013

The fluorescent proteins are generally denatured by heat treatment and thus lose their color. The normal reeling method includes processing by drying and cooking the cocoons near $100^{\circ}C$ before reeling. Therefore, the usual processing method cannot be used for making colored fluorescent silks. To develop a method that is applicable to producing transgenic silk without color loss, we develop reeling methods adequate for a recombinant fluorescence cocoons. It was found that the fluorescence cocoons keep their native color when dried at temperatures lower than $60^{\circ}C$ for 15 h. Also, a new cooking method to soften the fluorescent cocoons was developed: the cocoons were soaked in a solution of 0.2% sodium carbonate ($Na_2CO_3$)/0.1% nonionic surfactant (Triton X100) at $60^{\circ}C$ and then placed under vacuum. The repeated vacuum treatments enabled complete penetration of the solution into the cocoons, and the cocoons were thus homogenously softened and ready for reeling. In this state, the cooked cocoons can be reeled by an automated reeling machine. Our results suggest that drying and cooking of the cocoons at low temperature enables the subsequent reeling of the colored fluorescent silks by an automatic reeling machine without color loss and can produce silks that can be used for making higher value-added silk materials.

• Journal of Sericultural and Entomological Science
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• v.15 no.1
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• pp.27-30
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• 1973

The present research has been carried out in an attempt to obtain fundamental data which contribute to enhansing the accuracy of cocoon reeling test and improving the method of it more effectively. The results obtained are as follows: 1. The standard deviation and coefficient of variation of percentage of reelability and of percentage of raw silk yield to the sample size tended to show a gradual decrease according to the increasing of the sample size. However, the significant differences in the standard deviation and coefficient of variation of percentage of reelability and of percentage of raw silk yield between the different sizes of the samples having more than 300 cocoons have not been observed according to their sizes. 2. The significant difference in the standard errors from percentage of reelability between the samples of 300 cocoons and 400 cocoons have not been observed. 3. The significant difference in the standad errors from percentage of raw silk yield between the samples of 300 cocoons, 500 cocoons and 600 cocoons have not been observed. 4. The significant difference in the standard deviation, the standard errors and coefficient of variation to the length of a bave between the different sizes of the samples have not been shown. 5. From the above result, it is estimated that the optimum sire of the sample for the cocoon reeling test is the 300 cocoons.