Study of the structure of degummed Antheraea assamensis (muga) silk fibre

The paper discusses a special type of silk (muga silk) produced by the moth Antheraea assamensis (Lepidoptera: Saturniidae), which is available in the north east region, particularly in Assam, India. The structure of the degummed muga silk fibre is characterised by spectroscopy and X‐ray diffraction. An attempt has been made to establish a correlation between the orientation of the protein of the fibre and the mechanical properties of the fibre. Inter‐conversion of the α‐ and β‐phases of proteins is very common, and in some cases, both the phases may be present. Since muga silk is a protein fibre, there is a strong possibility of exhibition of this inter‐conversion property. The results show that the structure of muga fibre is made up of four molecular chains contained in a primitive tetrahedral cell with an average cell edge a _o = b ₀ = 746 pm and c ₀ =738 pm (fibre axis) and lattice number 8. The space group of the α‐phase is P4₁, with screw axis 4₁. The α‐phase accounts for rigidity and crystallinity, while the β‐phase accounts for extensibility and the amorphous state of the fibre.     

Demineralization of cocoons of Antheraea assamensis Helfer (muga) for effective reeling

Muga cocoons are evidenced of possessing heavy deposition of minerals (such as calcium oxalate) on its surface. This mineral deposition restricts reeling of muga fiber in comparison to the cocoons of mulberry silkworm. In this study, we have attempted to wash out the mineral layer using various chemical and natural agents like ethylenediaminetetraacetic acid (EDTA), potassium carbonate, citric acid, extract of Musa balbisiana (‘kolakhar’), and Citrus limon (lemon), respectively. It is observed that both the natural and chemical agents carefully removes the mineral deposition, leaving the gummy sericin substantially intact, preventing entanglement of fibroin brins, and permitting wet reeling with very minimum number of fiber breaks compared to commercial degumming. The removal of granular minerals was evidenced by surface morphology and FTIR spectroscopy of demineralized cocoon fiber. Further, the tensile strength of demineralized fiber showed superiority in contrast to sodium carbonate degummed fiber. Under the implemented experimental conditions ‘kolakhar’ functioned as the most efficient demineralizing agent amongst all. Therefore, the present study demonstrates an improved method for softening wild silk cocoons in contrast to harsh degumming for obtaining long continuous reeled fiber threads with very less number of fiber breaks and enhanced mechanical strength.     

Impact of BSA and casein on chemical modification of muga silk fiber

The study reports on the effects of bovine serum albumin and casein on grafting of muga (Antheraea assamensis Helfer) silk fibers using initiator 2,2’ azobisisobutyronitrile. FTIR studies confirm the chemical binding of the proteins onto muga fibers through shifting of the major amide bonds, accredited to grafting. Scanning electron microscopy imaging reveals rugged morphology of the grafted fibers, due to the imprints of granular proteins. Tensile strength of the fibers increases with the augmentation in grafting percent. The grafted fibers showed no loss in weight after chemical resistance measurement indicating stable bond formation between the proteins and the fibers. Moreover, the water retention capacity and dynamic contact angle study of grafted fibers suggest better hydrophobicity. Thus, the use of such eco-friendly grafting agents for enhancing the strength and stability of silk fiber proves to be more beneficial than to other chemical grafting agents in producing efficient and environment-friendly silk for various applications in textile and other biomaterial fields.     

Dyeing of silk fabric with natural dyes extracted from cochineal (Dactylopius coccus Costa) and gall oak (Quercus infectoria Olivier)

Silk fabric samples were mordanted with alum [KAl(SO₄)₂.12H₂O]. Then, the samples were dyed with cochineal (Dactylopius coccus Costa) and gall oak (Quercus infectoria Olivier) shellac extracts. Optimum dyeing parameters were determined by using different concentrations of these natural colorants. All the dyed samples were cut into two equal pieces. One group of the parts were post-mordanted with FeSO₄. A reserved-phase high-performance liquid chromatography (RP-HPLC) with the diode-array detection (DAD) method was utilized for the identification of the components of dyes present in the all dyed and post-mordanted samples. The color coordinates and fastness values of washing, perspiration, rubbing, and light were investigated and compared with each other. Using a mixture of these natural dyes enhanced the exhaustion of the dye and good color fastness test results were achieved.     

丝素蛋白/聚左旋乳酸纳米纤维纱线肌腱补片的制备及其性能

针对用于纺织肌腱补片的纯微米纱线结构生物活性低、免疫原性强和不可降解的缺陷,从补片材质和结构优化角度出发,构建了几种可生物吸收的纳米结构肌腱补片,以自制的丝素蛋白(SF)/聚左旋乳酸(PLLA)纳米纤维纱线为纬纱,以传统PLLA微米纤维纱线为经纱,经机织工艺加工成形。系统研究了SF和PLLA组分配比对补片形态结构、理化性能以及生物性能的影响。结果表明：补片均在约16.4°出现了结晶衍射峰,且随着SF占比的增加,补片的结晶度和力学性能均逐渐降低,但其断裂载荷均在100 N以上,可满足实际应用需求,且补片的细胞黏附和增殖能力均随SF质量分数的增加逐渐增强。     

TiO2-Ag/聚乳酸纳米复合纤维的制备及其抗菌性能

为赋予聚乳酸(PLA)纤维高效的抗菌性能,采用熔融共混纺丝法分别制备了不同质量配比的二氧化钛接枝银纳米介孔微球(TiO₂-Ag)/PLA纳米复合纤维和一定组成的TiO₂/PLA纳米复合纤维,并对2种纤维的结构、热性能和抗菌性能等进行表征和分析。结果表明:当TiO₂-Ag和TiO₂这2种纳米粒子添加质量分数不超过3%时,可在PLA基体中较均匀地分散;2种粒子的加入均不影响PLA的玻璃化转变温度和结晶结构,但会使其熔融温度和热稳定性下降,加入质量分数为3%的TiO₂后,导致PLA的结晶温度略有下降;随着TiO₂-Ag质量分数的增加, TiO₂-Ag/PLA纳米复合纤维对金黄色葡萄球菌和大肠杆菌的抑菌率不断增加;添加相同量的2种纳米粒子时,TiO₂-Ag/PLA复合纤维对2个菌种的抑制效果明显优于TiO₂/PLA复合纤维。     

Effects of sodium bicarbonate containing traces of citric acid in combination with sodium chloride on yield and some properties of white shrimp (Penaeus vannamei) frozen by shelf freezing, air-blast and cryogenic freezing

Effects of sodium bicarbonate with traces of citric acid in combination with sodium chloride on yield, freezing time, freezing rate, freezing loss and cutting force of white shrimp frozen by shelf, air-blast and cryogenic freezing with/without precooking were investigated. Shelf freezing was done at −40 °C ± 2 °C while air-blast freezing was carried out at −35 °C ± 2 °C, and cryogenic freezing was done at −35 °C, −40 °C and −60 °C. The freezing loss in the non-treated samples was 8.25, 4.6-5.84 and 1.92-3.48 g/100 g fresh shrimp for peeled samples frozen without precooking and increased to 21.85, 17.54-26.97, 17.92-20.31 g/100 g fresh shrimp in the precooked samples frozen by shelf, air-blast and cryogenic freezing, respectively. The treatment of sodium bicarbonate containing traces of citric acid at 4 g/100 ml with sodium chloride at 3 g/100 ml lead to the increase of yield thus reduced the freezing loss by about 6.83-10.28 and 6.41-12.4 g/100 g fresh shrimp for the frozen-thawed samples frozen as uncooked and cooked products, respectively. The toughening of shrimp was observed while sodium bicarbonate containing traces of citric acid treatment with sodium chloride could reduce the texture change occurred during the freezing.