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Covalent Immobilization of Organophosphorus Hydrolase oto Insoluble Bovine Collagen Fibers 
by Yanhong Li, Xinju Jia and Biyu Peng
Volume: 109      Number: 6     Page: 197-206     Year: 2014
An organophosphorous hydrolase (OPH) was prepared and partially purified from Flavobacterium sp. The crude enzyme, with an activity of 1030U/g, was immobilized onto insoluble bovine collagen fibers (hide powder), instead of collagen membrane, through glutaraldehyde coupling. Optimal conditions of enzyme immobilization and properties of the immobilized enzyme preparation were investigated. Compared to glutaraldehyde tanned and chrome tanned hide powders, non-tanned hide powder showed higher immobilized enzyme activity. The optimal enzyme immobilization conditions are as follows: 10mg of enzyme was immobilized onto 500mg of hide powder in a 50mM phosphate buffer of pH 7.5 at 200C, and 20% glutaraldehyde offer (based on the hide powder weight) was used to couple the enzyme and collagen fibers. The enzyme activity yield was about 35% and the hide powder immobilized OPH has an enzyme activity of about 7U/g. The immobilized enzyme showed the same temperature and pH profiles as the free enzyme, and it performed at much higher pH and with better thermal stability. The Km value of the immobilized enzyme was a somewhat higher (0.388mM) than that of the free enzyme (0.215mM). The reusability test showed that about 85% activity was retained after 10 use cycles. After storing for eight months at 20oC, the residual activity of the immobilized enzyme preparation was 98%.
 
 
1-Butyl-3-Methylimidazolium Acetate as an Alternative Solvent for Type I Collagen 
by Jie Liu, Zhou Xu, Yi Che, Haojun Fan and Bi Shi
Volume: 109      Number: 6     Page: 189-196     Year: 2014
Low solubility and undesirable denaturation in conventional solvents continue to represent a significant challenge for efficient extraction, accurate characterization and versatile processing of collagen. In the present study, a room temperature ionic liquid (IL), 1-butyl-3-methylimidazolium acetate ([BMIM]Ac), was synthesized, and then evaluated as an alternative solvent for type I collagen. Real-time polarizing optical microscope observation indicated complete disintegration of hierarchical structure of collagen aggregates as solubilized in [BMIM]Ac at 25 oC. The solubility reached up to approximately 8.0 wt.% at 25 oC, more than ten times higher than that in conventional dilute acetic acid. In comparison with dilute acetic acid and recently reported chloridion ILs, high solubility of collagen in [BMIM]Ac at room temperature was ascribed to loose binding between [BMIM]+ and acetate, as well as stronger proton-accepting ability of [BMIM]Ac, which enabled rupture of those intermolecular hydrogen bonds and ionic bonds that stabilized collagen aggregates. However, such bond-rupturing effect was found selective at room temperature. As demonstrated by Fourier transform infrared, circular dichroism, atomic force microscope, and ultrasensitive differential scanning calorimetry analysis, [BMIM]Ac did not destroy the special triple-helical structure of tropocollagen molecules that had been identified as being of importance for the functional and bioactive properties of collagen. According to these results, the discovery of [BMIM]Ac as an ideal solvent for collagen may open up new possibilities for the chemistry and engineering of collagen, which has long been established as a readily accessible and renewable resource with many unique properties.
 
 
Green Synthesis of Monodispersed Iron Oxide Nanoparticles for Leather Finishing 
by M. Nidhin, R. Aravindhan and K. Sreeram
Volume: 109      Number: 6     Page: 184-188     Year: 2014
Industries worldwide, including leather, have had to phase out pigments based on lead, chromium(VI), cadmium etc. due to the toxicity associated with these transition metal ions. Coupled to this phase out is also a need to enhance the functional properties of the otherwise safe pigments, with low use, so as to avoid wastage. In this direction, the use of nano-pigments is slowly coming into vogue. This paper explores the advantages of replacing an otherwise popular brown pigment – the hematite (á-Fe2O3) with nanosized oxides in leather finishing. Any synthesis methodology for nanoparticles is sustainable only when green methods are employed for their synthesis. This work takes adequate care in employing an environmentally friendly methodology based on biocompatible polysaccharide – starch as a template. The advantages of this method, such as the monodisperse character of the oxide, low particle size, ability of the carbon residue from the template to aid easy homogenization of the pigment to the finish formulation have resulted in excellent covering of surface, improved levelness, no overloading of grain, excellent physical properties and ageing resistance.
 
 
Transposition of Chrome Tanning in Leather Making 
by Chao Wu, Wenhua Zhang, Xuepin Liao, Yunhang Zeng and Bi Shi
Volume: 109      Number: 6     Page: 176-183     Year: 2014
To avoid the release of chrome from leather into post tanning effluents and the generation of chrome shavings, an inverse chrome tanning technology based on wet white was investigated. Conventional bated pelt was firstly tanned using an amphoteric organic tanning agent (Tingjiang white tanning agent, TWT) without pickling. Then, the TWT tanned wet white was directly processed with conventional post tanning processes. Chrome tanning was transposed to the end of the post tanning. The wet white had a shrinkage temperature (Ts) around 85oC that met the needs of shaving operation, and did not generate chrome shavings. The Ts and Cr2O3 content of the leather, by using this inverse chrome tanning technology, were higher than those of the conventional chrome tanned leather. With this inverse technology, the chrome output was reduced by 48%, mainly because no chrome was released from leather in post tanning processes. Meanwhile, the volume of chromium-containing wastewater discharged from the inverse processes was barely 31% of that from the conventional processes, which makes it much easier to collect and recover chromium from the effluents. Additionally, the tensile strength, tear strength and general appearances of the leather produced by the inverse technology were comparable to those of the conventional chrome tanned leather.
 
 
STUDIES OF ETHIOPIAN SHEEPSKINS AS AN OPPORTUNITY FOR VALUE ADDITION PART II: OPTIMIZATION AND CHARACTERIZATION OF WANKE UPPER AND GARMENT LEATHERS 
by H. MOHAMMED, G. AYSANEW, R. ARAVINDHAN, J. RAGHAVA RAO and N.K. CHANDRA BABU
Volume: 109      Number: 5     Page: 161-170     Year: 2014
Ethiopian tanners face a shortage of raw material input for the production of leather. The government strategically planned for importing raw skins from neighboring countries and also for effective utilization of available raw material resources in the country. The meat of Wanke sheep is in high demand in international markets, but the skin commands low price not only due to low availability but also less demand by tanners due to natural problems associated with the skin. Hence, tanners treat the skin as a reject. The problems of Wanke skin include high natural fat deposition, thin substance and low strength. Usually, leathers made out of Wanke skins have low selections compared to Ethiopian sheep skins and are mainly utilized for making lining leather. In this work, efforts have been made to develop a process technology for making high value leathers with improved properties from Wanke sheepskin.
 
 
NUTRIENT BALANCE IN AEROBIC BIOLOGICAL TREATMENT OF TANNERY WASTEWATER 
by JIANFEI ZHOU, YA-NAN WANG, WENHUA ZHANG AND BI SHI
Volume: 109      Number: 5     Page: 151-160     Year: 2014
The effect of nutrient composition of tannery wastewater on aerobic biological treatment, particularly on the removal of ammonia nitrogen (NH3-N) and total nitrogen (TN) was investigated based on the theory of nutrient balance. During the biological treatment of conventional tannery wastewater, total organic carbon (TOC) and total phosphorus (TP) were almost exhausted. However, the removal of TN was unsatisfactory, suggesting that tannery wastewater contains excessive N source and insufficient C and P sources. When extra C and P sources were added together into the wastewater, the removals of NH3-N and TN increased significantly. Under the optimal ratio of TOC:TN:TP (10:1:0.2), the removals of NH3-N and TN were 100% and 80%, respectively, and the added C and P sources were almost consumed by activated sludge. This means that a good nutrient balance was achieved in this condition. Accordingly, when ammonium salts are replaced by organic acids and phosphates in the deliming and bating processes, it is reasonable to assume that the change of wastewater composition would favor the aerobic biological treatment of wastewater.
 
 
Skin Characteristics of Cervus elaphus L. from Republic of Tuva in Russia 
by Urana Dandar, Selime Menteº Çolak, Remziye Deveci,
Volume: 109      Number: 5     Page: 141-150     Year: 2014
Characteristics of an animal raw skin are closely related to the physical properties of finished leather obtained from the skin. Although numerous studies have been performed on determination of physical properties of tanned deerskin, characteristics of raw deerskin have not yet been described in literature. In the present study, data on morphological, histochemical and chemical characteristics of wild red deer (Cervus elaphus L.) skins obtained from Republic of Tuva within the Russia Federation are presented and the relevant differences between skins of other animal species described. Table Top Scanning Electron Microscopy (TSEM) and Scanning Electron Microscopy (SEM) were used to determine the morphological characteristics of raw deerskins. For histochemical studies the cross section of skins were observed by Research Microscopy (RM). Hydroxyproline content, Total Kjeldahl Nitrogen (TKN), volatile matter, fat content, water-soluble-matter, sulphated total ash and fatty acid contents of raw deerskins were analyzed to further characterize the chemical composition of deerskin. Deerskin has comparatively higher TKN values, lower fat content with higher unsaturated fatty acid ratio, when compared to sheepskin. TSEM and SEM analysis showed that fur fibers and guard hairs of red deer skin were characterized by large cortex and medulla respectively that provides good isolation properties. In addition, high hydroxyproline content, low fat content, and tightly packed collagen fibers revealed by histochemical observations consolidates the long lasting property of deer skin. Assessment of skin characteristics enabled gathering data on physical and chemical properties of red deer skin, which is significant in choosing appropriate potential raw material that will produce the most suitable leather for a specific application.
 
 
DIFFUSION AND REACTION BEHAVIOR OF PROTEASES IN CATTLE HIDE MATRIX VIA FITC LABELED PROTEASES 
by Jianzhong Ma, Xueyan Hou, Dangge Gao and Jing Zhang
Volume: 109      Number: 5     Page: 131-140     Year: 2014
Enzymes play an important role in the biological treatment of animal skin collagen in the leather making process. In this work, three proteases (2709, LimeG and SoakL) with different molecular weight were used in the treatment of cattle hide. Protein and hydroxyproline absorbance was measured to evaluate the treatment effectively. Proteases labeled by Fluorescein Isothiocyanate (FITC) were used to treat the cattle hide to observe the diffusion and reaction behavior of proteases in cattle hide matrix. The results indicate that when the cattle hide was treated with smaller molecular weight protease, the degradation degree of the protein and collagen was more than that of the cattle hide treated with larger molecular weight protease. The fluorescence microscopy images demonstrate that during the early stages, proteases chiefly diffused into the cattle hide matrix through pores and hair follicles, and then diffused into the inner layer via hair follicles to hydrolyze inter-fibrillary proteins for opening up collagen fibers. In the present investigation, a visible assessment for the diffusion and reaction behavior of proteases in the enzymatic treatment of cattle hide matrix was reported.
 
 
Development of Alginate-Chitosan Based Biopolymers for Leather Retanning 
by R. Aravindhan, K. Sreeram and J. Rao
Volume: 109      Number: 4     Page: 99-109     Year: 2014
Hides and skins when received in tanneries have closely and firmly packed together bundles of collagen fibers, with elastin and other non-fibrous proteins aiding a dense structure formation. However, in order to ensure the easy diffusion of chemicals, a series of pre-tanning operations ensure the opening up of the fiber bundles and the removal of the non-fibrous materials, resulting in a loose structure. A majority of leather consumers often demand properties, which were available on hides and skins, but lost during the pre-tanning operations. One such property is the compaction or firm packing of fiber bundles. While vegetable tanning processes provide for good fullness and firm packing of fiber bundles, the lack of strength and stability against wet heat forces the tanners to adopt chrome tanning. Chrome tanning provides for good inter and intra networking of fibers, but is unable to replenish the firmness found in the original raw material. To overcome this drawback, tanners often resort to the use of a combination of retanning agents in varying proportions. The varying character of these products results in non-uniform and poorer uptake. In this work an attempt has been made to develop syntans from biopolymers such as chitosan and alginate, which could provide fiber compaction to the leather.
 
 
The Role of Neutral Salt for the Hydrolysis and Hierarchical Structure of Hide Fiber in Pickling 
by Haiming Cheng, Min Chen and Zhiqiang Li
Volume: 109      Number: 4     Page: 125-130     Year: 2014
Pickling process carried out for adjusting the skin to the desired pH for tanning, in which neutral salts were added to avoid skin fiber from the acid swelling. This research study aimed at investigating the contribution of neutral salt to the hydrolysis and the fibrous structure of collagen fiber in acid solutions. Collagen fiber and bovine hide in sulfuric acid solutions with sodium chloride or sodium sulfate were investigated. The total protein concentration in the solutions was determined. The hierarchical structures of bovine hide in different acid and neutral salt systems were investigated by optical microscope, TEM and SEM. This study suggested the importance of neutral salt for the hydrolysis and the dispersion of collagen fiber in pickling. It implied that the osmotic swelling by acid could not reach the inner scale of fibril. The decrease in mechanical properties for the leather tanned with salt free pickling may have been caused by osmotic swelling destroyed the interactions among the fibril and fiber bundles.