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Reaction of Protein and Carbohydrates with EDC for Making Unique Biomaterials 
by M. Taylor, L. Bumanlag, E. Brown and C.-K. Liu
Volume: 111      Number: 4     Page: 155-164     Year: 2016
Prior research from this laboratory has demonstrated the feasibility of using chemical and enzymatic treatments on protein and carbohydrate waste products for the purpose of making fillers to enhance the properties of leather. These treatments (microbial transglutaminase, genipin, and polyphenols in the form of vegetable tannins), were effective in reacting with gelatins, whey protein concentrate (WPC), and/or chitosan, alone or in combinations, to give products with interesting functional properties. All crosslinkers were either natural products and/or sustainable materials. In our continuing studies of chemoenzymatic methods to crosslink collagen and collagen by-products, we investigated the extensively reported 1-ethyl-3-(3 dimethylaminopropyl) carbodiimide hydrochloride (EDC), which has been used to crosslink proteins for purpose of making biomaterials. This present study examined the reactivity of various concentrations of EDC with gelatin, chitosan and combinations of both, in the presence and absence of N-hydroxysuccinimide (NHS) at optimal times, and temperatures, and the effect these parameters had on physical properties, molecular weight distribution and free amine content. It was found that both gelatin and chitosan had reactivity with EDC and the physical properties reflected the concentration of both the carbodiimide and gelatin. It was found however that when the gelatin and chitosan were reacted together in the presence of the carbodiimide, the physical properties improved significantly over the protein and carbohydrate when reacted separately, resulting in unique products. This study provides a better understanding of the reactivity of carbodiimide and optimal conditions for developing appropriate products.
 
 
A Polyurethane-based Retanning Agent with Fluorescent Effect 
by Saiqi Tian, Peikun Zhang, Haojun Fan, Yi Chen, Jun Yan and Bi Shi
Volume: 111      Number: 4     Page: 148-154     Year: 2016
A novel fluorescent waterborne polyurethane retanning agent (FWPRA) was prepared through chemically incorporation of fluorescer, disodium 4, 4’-bi s[4 - a n i l i no - 6 - hydroxyethylamino-6-(2-choloronilino-1,3,5 triazin-2-yl) amino]stilbene-2,2’-disulphonate (RSW), into polyurethane backbone as a chain extender. The chemical structure was characterized by FTIR, 1H NMR and UV−vis spectrophotometer, and fluorescence performances of FWPRA, RSW together with resultant leather were investigated systematically. The results indicate that polymerization has a positive effect on optical performance; FWPRA shows enhanced fluorescence intensity in comparison with fluorescer RSW. In the retanning process, no decay of optical performance can be found when chromium(III) salt and chestnut extract are used together, which reveals that FWPRA presents good fluorescence stability to other chemicals. For wet blue retanned by FWPRA, the shrinkage temperature, thickness as well as mechanical properties are improved. Most importantly, the resultant leather exhibits magic fluorescence effect under UV lamp.
 
 
Soluble Collagen Approach to a Combination Tannage Mechanism 
by E. Brown, M. Taylor and C.-K. Liu
Volume: 111      Number: 4     Page: 141-147     Year: 2016
Although complex salts of CrIII sulfate are currently the most effective tanning agents, salts of other metals, including aluminum, have been used either alone or in combination with vegetable tannins or other organic chemicals. In the present study, the interactions of aluminum sulfate, and quebracho or chestnut tannins with collagen were investigated. A model system was devised to use soluble collagen in one compartment of an equilibrium dialysis cell and solutions of mineral or polyphenolic tanning agents in the other compartment. This study, by focusing on the effects of tanning agents on soluble collagen, rather than on intact hide, or powdered hide, gives a somewhat different perspective on the tanning process. The extraction of water from the collagen solution in the formation of aluminum/tannin complexes suggests that the lowering of water activity around the collagen may play a role in stabilizing a collagen/tannin/aluminum tannage. The most interesting finding is that aluminum which has little effect on collagen helical structure and stability does appear to connect collagen molecules in some manner to produce high molecular weight species that do not separate under the conditions of SDS PAGE. Comparison of the interactions of various combinations of minerals and vegetable tannins with collagen is expected to provide insight into a more generalized mechanism for tanning.
 
 
Effect of Fatliquoring on Grain and Corium Quality of Leather Assessed by Ball Bursting and Tearing Tests 
by A. Manich, J. Barneys, L. Martinez, J. Lloria and A. Marsal
Volume: 111      Number: 4     Page: 127-140     Year: 2016
Leather quality depends largely on the physical, mechanical and organoleptic characteristics of the finished leather from which the final articles are manufactured. Tearing strength and ball burst tests are especially relevant for leather goods that will be subjected to significant tearing and bursting stresses during use. The influence of different fatliquors on tearing and ball burst tests is studied using wet-blue leathers from Ireland as starting material. Leathers were retanned and dyed following a conventional process and then, they were fatliquored with nine different fatliquoring agents provided by Trumpler Española. A 7% of active matter (on shaved weight) was applied. After a final washing, a sample of the treated leathers was kept in "crust" state (without finishing), and the rest received a light finishing process following a conventional recipe. To estimate differences between sides, the central parts of them were fatliquored with the same combination used as reference (sulphited triglycerides of rapeseed oil/fatty polymer). The characteristic components of the fatliquoring agents used were a) Soy lecithin, b) Sulphited triglycerides of rapeseed oil, c) Acrylic polymer (waterproofing agent), d) Fatty Polymers (sarcosinates), e) Sulphated triglycerides of rapeseed oil, f) Phosphoric Ester, g) C14 Paraffin, h) Sulphonated paraffin, and i) Sulphited fish oil. Based on the experimental results, treatments with similar effects on tearing and ball burst test behavior were grouped, clustering the fatliquors with similar effects on these characteristics when compared with the results of the nonfatliquored leather. The effect of finishing has also been studied.
 
 
Structural Differences Between Commercial Acacia Mangium Tannin and Its Effluent 
by Bo Teng, Ziaoyun Jian, Yanping Gao, Jinwei Zhang and Wuyomg Chen
Volume: 111      Number: 3     Page: 92-100     Year: 2016
Recycling and reuse techniques provide an efficient way to overcome the environmental issues of the chrome tanning effluent. However, only few vegetable tanning related recycling techniques were developed due to the limited information about the effluent. In this study, a common vegetable tanning process was performed with a commercial Acacia Mangium tannin (CAMT) to produce Acacia Mangium tanning effluent (AMTE). The tannins in the AMTE and CAMT were characterized using Fourier transform infrared, nuclear magnetic resonance spectroscopy, matrix assisted laser desorption/ ionization time of flight mass spectrometry, gel permeation chromatography and elemental analysis. The results showed that the stereochemistry and flavan-3-ol subunits of the tannins in the AMTE were the same with the CAMT. However the differences between the tannins in the AMTE and CAMT were presented in terms of the tannin category, molecular weight, and quantities of sulfo acid group. Tannins in the AMTE were mainly composed of procyanidin, while prodelphinidin and procyanidin content showed comparable in the CAMT. Average molecular weight of the AMTE was 1315Da, in contrast to an obviously higher value in the CAMT (2025Da). Meanwhile, higher sulfonic acid group content was also found in the AMTE. These differences were deduced in accordance with the collagen binding ability of the tannins. Results will be valuable for reuse and recycling of vegetable tanning effluent.
 
 
Development of a New Leather Intermedidate: Wet-bright with a High Dye Affinity 
by A. Bacardit, M. Gonzalez, S. Van der Burgh, J. Armengol and L. Olle
Volume: 111      Number: 3     Page: 113-122     Year: 2016
In this work we develop a new tanning process (that we call wet-bright) that produces leather free of chromium, aldehydes, aldehyde precursors and organic solvents. Due to the mineral character of the new system, the leather offers a perfect dyeability and high dye affinity, allowing for very bright colors in all leather applications. The leathers offer a perfect dyeability due to the brilliant whiteness of the wet-bright intermediate. This new system consists of the application of Tanfor TTM system (from Kemira) which is safe for both humans and environment and is not classified as hazardous. In addition, when compared to existing traditional processes, there are economic and environmental advantages resulting from the use of this new system.
 
 
Early Detection of Looseness in Bovine Hides Using Ultrasonic Imaging 
by H. Wells, G. Holmes and R. Haverkamp
Volume: 111      Number: 3     Page: 107-112     Year: 2016
The processing of bovine hides to leather results in a significant proportion of defective leather known as loose leather. It has not previously been possible to recognize hides that may produce loose leather. Hides were processed through to leather with samples retained at the pickle, wet blue and crust leather stages with material that resulted in loose leather compared with that resulting in tight leather, using ultrasonic imaging. The loose precursor is characterized by a lower density of material in the mid grain layer. The looseness is quantified by amplitude differences in ultrasound line scans or cross-sectional area scans between loose leather and tight leather with 2-4 times the amount of low intensity area in loose leather at all three process stages. This enables detection of hides that will result in loose leather and may enable unsuitable hides to be diverted to other process streams to save substantial processing costs.
 
 
A Further Investigation on Collagen-Cr(III) Interaction at Molecular Level 
by Weimo Han, Yunhang Zeng and Wenhua Zhang
Volume: 111      Number: 3     Page: 101-106     Year: 2016
As we know, the reaction of chrome tanning primarily occurs at carboxyl groups of collagen, tacitly assumed at aspartic and glutamic side chains. However, the differences of the reactivity and reaction extent at these sites, as well as the effect of environmental conditions on the reaction are still unclear at molecular level. This paper presents a theoretical analysis of the reactivity of collagen carboxyl groups and Cr(III) species based on electrophilicity index (ù), and the driving force for tanning reaction by using density functional theory (DFT) with Lanl2dz for chrome atom and 6-31g(d) for non-metal atoms. Glutamatic acid (Glu) and aspartatic acid (Asp) were used as the models of collagen side chains containing carboxyl group. Based on visual minteq calculation, the main Cr(III) species in chrome tanning liquor were found to be Cr(SO4)(H2O)4 +, Cr(H2O)6 3+, Cr2(OH)2(H2O)8 4+, and Cr3(OH)4(H2O)10 5+ under the pH range of tanning process, and the content of multi-nuclear Cr(III) species increases with the rise of pH. The reactivity of collagen carboxyl groups is in the sequence of ionized Asp (Asp-) > ionized Glu (Glu-) > unionized Glu > unionized Asp, while the reactivity of the main Cr(III) species is sequenced by Cr3(OH)4(H2O)10 5+ > Cr2(OH)2(H2O)8 4+ > Cr(H2O)6 3+ > Cr(SO4)(H2O)4 +. The data of thermodynamic driving force for tanning reaction indicate that ionized carboxyl groups have stronger tendency to form more stable carboxyl-C (III) complexes compared with unionized carboxyl groups, and the order of the tendency is Glu- > Asp- > Asp > Glu. Obviously, for Glu- and Asp- or Glu and Asp, the thermodynamic driving force is exactly the opposite with reactivity. Therefore, as for collagen carboxyl groups, the predominant reaction bonding site is determined by both thermodynamic and kinetic conditions. As for Cr(III) species, the order of thermodynamic driving force is Cr3(OH)4(H2O)10 5+ > Cr2(OH)2(H2O)8 4+ > Cr(H2O)6 3+ > Cr(SO4) (H2O)4 + which is consistent with the order of reactivity.
 
 
Control of Microorganisms on Tanned Leather: From Fungicide to Antimicrobial Function Leather 
by Haibin Gu, Li Zhao, Jun Ma, Yingjie Yang, Changqing Zhao and Wuyong Chena
Volume: 111      Number: 2     Page: 69-87     Year: 2016
To inhibit the microbial growth on tanned leathers including wetblue, crust leathers, finished leathers and their goods (shoes, garments, bags, etc.), fungicides are usually applied during various leather-making processes. Under the situation of increasingly strict environmental legislation, all kinds of ecofriendly fungicides were explored recently to replace the currently used noxious ones in leather industry. Meanwhile, a nontraditional new type of leather, called antimicrobial function leather, attracted more and more attention from leather chemists and technologists, because of its tempting antimicrobial protection provided and wide application prospects in many fields such as medical materials, health products, daily products, public transport vehicles, and so on. Based on the literatures published in the past decade, especially in the past five years, this review systematically and comprehensively summarizes current status and development trend about leather fungicides and antimicrobial function leather. The discussed antimicrobials contain traditional organic synthetic fungicides with small molecular weight, natural essential oils, macromolecular polymers and chitosan derivatives, and nano-inorganic antimicrobials (nanosilver, nano-ZnO, nano-TiO2, nano-SiO2, etc.). Finally, several proposals are addressed for the development of new leather fungicides and antimicrobial function leather, and especially, a new viewpoint, in which the antimicrobial leather is prepared based on various tanning mechanisms, is demonstrably presented to solve the problem of loose combination between antimicrobial substances and leather fibers.
 
 
Recovery, Purification and Reuse of Contaminated Sodium Chloride Obtained from Tanneries for Raw Goat Skin Preservation 
by N. Vedaraman, K. Sandhya, V. Brindha, A. Selvi, K. Velappan and C. Muralidharan
Volume: 111      Number: 2     Page: 62-68     Year: 2016
Large quantity of sodium chloride is used for raw skin preservation. Significant amount of salt is removed from raw skin through a mechanical process before taking for further processing in tanneries. This recovered salt is contaminated with various dirt, proteinous materials and microorganisms and gets accumulated, which creates a serious waste disposal problem for tanneries. In this study the recovered contaminated waste salt was purified and reused for skin preservation. The recovered contaminated salt from tannery was dissolved in water, filtered, treated with activated charcoal to remove the undesired components and subjected to ozone treatment for the removal of microbial contamination. The ozonized solution was subjected to solar evaporation. Improved evaporation techniques were employed to facilitate evaporation of salt solution. Dried purified salt obtained was checked for microbial contamination. Then the dry salt was used for the preservation of a fresh batch of animal skin. After a minimum storage period of 21 days, the skins were processed into leather as per the usual procedure and compared with the leathers obtained by conventional fresh salt preserved skins. The physical tests, chemical analysis and organoletic properties of experimental leathers show that the quality of leather obtained from animal skins preserved using purified salt was comparable to leathers obtained from conventional pure salt preserved skins. The approach minimizes salinity concerns of tanning by providing simple and practical solution.