A new approach for quantitative characterization of hydrolytic action of proteases to elastin in leather manufacturing.

Leather biotechnology based on enzyme is one of the main directions toward clean technology in the leather manufacturing process. Proteins such as collagen, elastin, and keratin are important components in animal hides or skins, and proteases are most frequently used in the leather manufacturing process for the removal of interfibrillar substance and opening-up of collagen fiber instead of toxic chemicals. Elastin is an important and highly elastic structural protein in the animal hides or skins and significantly affects the properties of the final leather product. For improving the quality of leather product, thorough understanding of the mechanism of action of proteases on elastin is necessary. The action of proteases on elastin has been mostly studied either qualitatively by histological analysis or quantitatively based on substrate casein or stained substrates, such as congo red-elastin and Remazol Brilliant Blue R-elastin; however, the resulting products have not been accurately characterized and thus these methods are not up to the standard. Besides, controlling the hydrolytic action of proteases to elastin has been very difficult, and excessive hydrolytic action of protease damages the elastin, restricting the wide application of proteases in the leather manufacturing process. In order to quantitatively evaluate the hydrolytic action of proteases on elastin in a more accurate manner, in this study, a new method was established by determining the unique amino acid desmosine based on the covalently bonded elastin-desmosine conjugate. Quantitative analysis of desmosine was performed in liquor based on cowhides substrate, and qualitative characterization was accomplished by histological analysis of elastic fiber in hides using an optical microscope. The results of this study indicated that the newly developed method is sensitive, accurate, and reproducible. In addition, the unhairing trials also demonstrated the suitability of newly established method in the leather manufacturing process to evaluate the action of proteases on the elastin in animal hides or skins.

Artisanal tanneries: Potential application of inoculants formulated with lactic acid bacteria.

In artisanal tanneries, the skins are immersed in cereals fermented by natural microbial flora in order to reduce the pH of the skin, an essential condition for carrying out the final step. The environmental thermal variation alters the fermentation process and affects the quality of the final product. The aim of this work was to isolate lactic acid bacteria from cereals mixture fermented in an artisanal tannery and to evaluate in vitro the acidifying activity of the strains as a first step for the formulation of a starter culture. In most samples, a prevalence of cocci (95%) was observed with respect to bacilli. The best acidifying strains were identified by phenotypic and genotypic techniques as Enterococcus faecium CRL 1943 (rapid acidification at 37 °C) and Leuconostoc citreum CRL 1945 (high acidifying activity at 18 °C). In addition, the biomass production of the selected strains was analyzed at free and controlled pH (bioreactors 1.5 L). The production of biomass was optimal at controlled pH, with a higher growth (0.5-1.1 log units). Both strains were compatible, allowing their inclusion in a mixed culture. These lactic strains could contribute to the systematization of the tanning process.

Artificially modified collagen fibril orientation affects leather tear strength.

BACKGROUND: Ovine leather has around half the tear strength of bovine leather and is therefore not suitable for high-value applications such as shoes. Tear strength has been correlated with the natural collagen fibril alignment (orientation index, OI). It is hypothesized that it could be possible to artificially increase the OI of the collagen fibrils and that an artificial increase in OI could increase tear strength. RESULTS: Ovine skins, after pickling and bating, were strained biaxially during chrome tanning. The strain ranged from 2 to 15% of the initial sample length, either uniformly in both directions by 10% or with 3% in one direction and 15% in the other. Once tanned, the leather tear strengths were measured and the collagen fibril orientation was measured using synchrotron-based small-angle X-ray scattering. CONCLUSION: The OI increased as a result of strain during tanning from 0.48 to 0.79 (P = 0.001) measured edge-on and the thickness-normalized tear strength increased from 27 to 43 N mm-1 (P < 0.001) after leather was strained 10% in two orthogonal directions. This is evidence to support a causal relationship between high OI (measured edge-on), highly influenced by thickness, and tear strength. It also provides a method to produce stronger leather. © 2017 Society of Chemical Industry.

1 H NMR study and multivariate data analysis of reindeer skin tanning methods.

Reindeer skin clothing has been an essential component in the lives of indigenous people of the arctic and sub-arctic regions, keeping them warm during harsh winters. However, the skin processing technology, which often conveys the history and tradition of the indigenous group, has not been well documented. In this study, NMR spectra and relaxation behaviors of reindeer skin samples treated with a variety of vegetable tannin extracts, oils and fatty substances are studied and compared. With the assistance of principal component analysis (PCA), one can recognize patterns and identify groupings of differently treated samples. These methods could be important aids in efforts to conserve museum leather artifacts with unknown treatment methods and in the analysis of reindeer skin tanning processes. Copyright © 2016 John Wiley & Sons, Ltd.

Tanning equipment use: 2014 Canadian Community Health Survey.

BACKGROUND: Tanning equipment use is related to the early onset of cancer, with the risk increasing as the duration and repetition of exposure increase. In 2009, the International Agency for Research on Cancer classified tanning equipment use as carcinogenic to humans, and according to the World Health Organization, the risk of skin melanoma increases significantly when use begins before age 35. DATA AND METHODS: The rapid response component of the 2014 Canadian Community Health Survey collected data on the use of tanning equipment in the previous 12 months, including reasons for use, frequency/duration of use, precautions taken, and adverse reactions or injuries. This analysis examines the prevalence of self-reported indoor tanning in a nationally representative sample of Canadians aged 12 or older in the 10 provinces. RESULTS: In 2014, 4.5% of Canadians (an estimated 1.35 million) reported that they had used tanning equipment in the past year; 70.3% of them were female, and just over half of female users were aged 18 to 34. The prevalence of indoor tanning was highest among people with some postsecondary education and among those in higher income households (trend p-value ⟨ 0.0001). Most users reported fewer than 10 sessions in the past year. The most common reason (62.0%) was to develop a "protective" base tan. INTERPRETATION: Females made up the majority of tanning equipment users, particularly at ages 18 to 34. Efforts to increase awareness of the risks may be beneficial, given the high percentage of users who believed that indoor tanning offers some level of skin protection from future sun exposure.

Total control of chromium in tanneries - thermal decomposition of filtration cake from enzymatic hydrolysis of chrome shavings.

This paper deals with the problem of chromium recovery from chrome-tanned waste and thus with reducing the environmental impact of the leather industry. Chrome-tanned waste was transformed by alkaline enzymatic hydrolysis promoted by magnesium oxide into practically chromium-free, commercially applicable collagen hydrolysate and filtration cake containing a high portion of chromium. The crude and magnesium-deprived chromium cakes were subjected to a process of thermal decomposition at 650°C under oxygen-free conditions to reduce the amount of this waste and to study the effect of magnesium removal on the resulting products. Oxygen-free conditions were applied in order to prevent the oxidation of trivalent chromium into the hazardous hexavalent form. Thermal decomposition products from both crude and magnesium-deprived chrome cakes were characterized by high chromium content over 50%, which occurred as eskolaite (Cr2O3) and magnesiochromite (MgCr2O4) crystal phases, respectively. Thermal decomposition decreased the amount of chrome cake dry feed by 90%. Based on the performed experiments, a scheme for the total control of chromium in the leather industry was designed.

MRI and unilateral NMR study of reindeer skin tanning processes.

The study of arctic or subarctic indigenous skin clothing material, known for its design and ability to keep the body warm, provides information about the tanning materials and techniques. The study also provides clues about the culture that created it, since tanning processes are often specific to certain indigenous groups. Untreated skin samples and samples treated with willow (Salix sp) bark extract and cod liver oil are compared in this study using both MRI and unilateral NMR techniques. The two types of samples show different proton spatial distributions and different relaxation times, which may also provide information about the tanning technique and aging behavior.

Hexavalent and trivalent chromium in leather: What should be done?

Trivalent chromium compounds are used for leather tanning, and chromium may be released during use of leather goods. In certain instances, small amounts of hexavalent chromium can be formed and released. Both trivalent and hexavalent chromium can elicit allergic skin reaction in chromium sensitised subjects, the latter being significantly more potent. Induction of sensitisation only occurs after exposure to hexavalent chromium. A minority of subjects are sensitised to chromium, and in a fraction of these subjects allergic skin reaction have been described after wearing leather shoes or, less frequently, other leather goods. The evidence that in all these cases the reaction is related to hexavalent chromium is not always strong. The content of hexavalent chromium in leather is regulated in European Union, but rate of release rather than content is relevant for allergic skin reaction. The role of trivalent chromium appear much less relevant if at all. Modern tanning procedure do not pose significant risk due to either hexavalent or trivalent chromium. Dismissing bad quality and worn-off leather goods is relevant in reducing or eliminating the skin reaction. It should also be pointed out that shoe components or substances other than chromium in leather may cause allergic/irritative skin reactions.

Interaction of collagen with chlorosulphonated paraffin tanning agents: Fourier transform infrared spectroscopic analysis and molecular dynamics simulations.

The binding of chlorosulphonated paraffins to collagen triple helices is studied by means of classical molecular dynamics simulations and experimental spectroscopic techniques in order to disclose the principal characteristics of their interaction during the leather fattening process. Indeed, collagen is the main target to develop new leather modifying agents with specific characteristics, and an accurate design of the collagen binders, supported by predictive computational strategies, could be a successful tool to obtain new effective eco-compatible compounds able to impart to the leather the required functionalities and distinctive mechanical properties. Possible effects caused by the tanning agents on the collagen matrix have been identified from both experimental and theoretical points of view. Computational data in agreement with experiment have revealed that chlorosulphonated paraffins can interact favorably with the collagen residues having amine groups in their side chains (Arg, Lys, Asn and Gln) and reduce the tendency of the solvated collagen matrix to swell. However, the interference of chlorosulphonated paraffins with the unfolding process, which is operated mainly by the action of water, can be due both to covalent cross-linking of the collagen chains and intermolecular hydrogen bonding interactions involving also the hydroxyl groups of Hyp, Ser and Thr residues.

A novel serine alkaline protease from Bacillus altitudinis GVC11 and its application as a dehairing agent.

A serine alkaline protease from a newly isolated alkaliphilic Bacillus altitudinis GVC11 was purified and characterized. The enzyme was purified to homogeneity by acetone precipitation, DEAE-cellulose anion exchange chromatography with 7.03-fold increase in specific activity and 15.25% recovery. The molecular weight of alkaline protease was estimated to be 28 kDa by SDS PAGE and activity was further assessed by zymogram analysis. The enzyme was highly active over a wide range of pH 8.5 to 12.5 with an optimum pH of 9.5. The optimum temperature of purified enzyme was 45 °C and Ca(2+) further increased the thermal stability of the enzyme. The enzyme activity was enhanced by Ca(2+) and Mg(2+) and inhibited by Hg(2+). The present study is the first report to examine and describe production of highly alkaline protease from Bacillus altitudinis and also its remarkable dehairing ability of goat hide in 18 h without disturbing the collagen and hair integrity.

Tannin fingerprinting in vegetable tanned leather by solid state NMR spectroscopy and comparison with leathers tanned by other processes.

Solid state ¹³C-NMR spectra of pure tannin powders from four different sources--mimosa, quebracho, chestnut and tara--are readily distinguishable from each other, both in pure commercial powder form, and in leather which they have been used to tan. Groups of signals indicative of the source, and type (condensed vs. hydrolyzable) of tannin used in the manufacture are well resolved in the spectra of the finished leathers. These fingerprints are compared with those arising from leathers tanned with other common tanning agents. Paramagnetic chromium (III) tanning causes widespread but selective disappearance of signals from the spectrum of leather collagen, including resonances from acidic aspartyl and glutamyl residues, likely bound to Cr (III) structures. Aluminium (III) and glutaraldehyde tanning both cause considerable leather collagen signal sharpening suggesting some increase in molecular structural ordering. The ²7Al-NMR signal from the former material is consistent with an octahedral coordination by oxygen ligands. Solid state NMR thus provides easily recognisable reagent specific spectral fingerprints of the products of vegetable and some other common tanning processes. Because spectra are related to molecular properties, NMR is potentially a powerful tool in leather process enhancement and quality or provenance assurance.

[Leather bags production: organization study, general identification of hazards, biomechanical overload risk pre-evaluation using an easily applied evaluation tool]. / Processo della pelle per la produzione di borse: studio organizzativo, identificazione generale dei pericoli, prevalutazione del rischio per il sovraccarico biomeccanico mediante un nuovo strumento di valutazione di semplice applicazione.

BACKGROUND: Craft industries are the backbone of the Italian manufacturing system and in this sector the leather trade plays a crucial role. OBJECTIVE AND METHODS: The aim of the study was to experiment with a risk pre-mapping data sheet in leather bag manufacture by analyzing the production cycle. RESULTS: The prevalence of biomechanical, organizational and physical factors was demonstrated in tanneries. With regard to chemical agents the lack of any priority of intervention could be due to the lack of information on the chemicals used. In the 2 enterprises that used mechanical processes the results showed different priorities for intervention and a different level of the extent of such intervention. In particular in the first enterprise biomechanical overload was a top priority, while in the second the results were very similar to those of the tannery. The analysis showed in both companies that there was a high prevalence of risk of upper limb biomechanical overload in leather bag manufacture. Chemical risk assessment was not shown as a priority because the list of chemicals used was neither complete nor sufficient. CONCLUSIONS: The risk pre-mapping data sheet allowed us to obtain a preliminary overview of all the major existing risks in the leather industry. Therefore the method can prove a useful tool for employers as it permits instant identification of priorities for intervention for the different risks.

Otzi, the iceman and his leather clothes.

Over 5000 years ago, a man climbed up to the icy heights of the glacier in South Tyrol, Italy and died. He was found by accident in 1991, with his clothes and equipment, mummified and frozen: an archaeological sensation and a unique snapshot of a Copper Age man. For several years highly specialised research teams have examined the mummy and all accompanying items. This paper describes how fur and leather clothes of the iceman could have been tanned. Details of the analytical tests undertaken on the 5000 year old leather samples and what they revealed are presented.

Optimization of a novel enzyme treatment process for early-stage processing of sheepskins.

An enzyme treatment process for early-stage processing of sheepskins has been previously reported by the Leather and Shoe Research Association of New Zealand (LASRA) as an alternative to current industry operations. The newly developed process had marked benefits over conventional processing in terms of a lowered energy usage (73%), processing time (47%) as well as water use (49%), but had been developed as a "proof of principle''. The objective of this work was to develop the process further to a stage ready for adoption by industry. Mass balancing was used to investigate potential modifications for the process based on the understanding developed from a detailed analysis of preliminary design trials. Results showed that a configuration utilising a 2 stage counter-current system for the washing stages and segregation and recycling of enzyme float prior to dilution in the neutralization stage was a significant improvement. Benefits over conventional processing include a reduction of residual TDS by 50% at the washing stages and 70% savings on water use overall. Benefits over the un-optimized LASRA process are reduction of solids in product after enzyme treatment and neutralization stages by 30%, additional water savings of 21%, as well as 10% savings of enzyme usage.

Sulphates for skin preservation--a novel approach to reduce tannery effluent salinity hazards.

In tanneries microorganisms are able to find environment suitable for their growth. Raw hide of buffalo and other animals like goat that are economically important, are an ideal source of nutrients for bacterial and fungal growth. In the past, preservatives like sodium chloride provided effective protection to fresh hides however the ill effect of their excessive use was not evaluated. But recently concern over potential ecological hazards has become more deliberate and sodium chloride features lot of disadvantages in agriculture as most of the tannery effluent is flown in agricultural fields in India. After rigorous laboratory experimentation on moisture content, SEM of hide, pure sodium sulphate as well as sodium sulphate in addition with sodium chloride (i.e. 10% w/w and 20% w/w) proved as most preferable option for curing of buffalo hide which gives effective preservation. Pollution load studies put forward sodium sulphate as an effective curing agent for buffalo hide to apply at industrial scale also.

An application of advanced hair-save processes in leather industry as the reason of formation of keratinous waste: few peculiarities of its utilisation.

The application of more environmentally friendly hide and skin unhairing technologies in leather processing results in a significant increase in keratin waste. There are currently two most promising hair-saving unhairing methods: enzymatic and hair immunisation. The complete use of hair-saving unhairing methods in the leather industry will lead to the formation of approximately 143 thousand tons of hair/wool waste annually, which will require disposal. The disposal of keratin wastes from the leather industry has not been adequately studied, bearing in mind the possible amount of such wastes that will be produced in the future. Unfortunately, existing studies pay little attention to the method of unhairing, even though the unhairing method has a vast influence on the properties of keratin in the obtained hair/wool wastes. Accordingly, the present research is an attempt to establish how the differently obtained keratin wastes behave following disposal. The obtained results have shown that waste wool is characterised by different behaviour during burial in soil, and the behaviour depends on the method of unhairing. This proposition is valid for waste wool bioresistance as well. It was concluded that the deterioration of any sort of keratinous waste from the leather industry should be investigated thoroughly before disposal by burial in landfills.

What determines compliance with cleaner production? An appraisal of the tanning industry in Sialkot, Pakistan.

Leather tanneries which produce significant amounts of solid waste, effluents, and emissions are a major contributor to industrial waste. A cleaner production program was launched by the government of Pakistan to implement the cleaner production measures for tanneries of Sialkot from 1999 to 2005. The main objective of this study is to identify the impact of a cleaner production program, along with other determinants of a cleaner production in the leather industry. The study analyses firm-level primary data collected from leather tanneries in Sialkot. The primary data were collected from tanneries in Sialkot. The econometric analysis is conducted using the Poisson regression analysis. Overall results show that there is no significant impact of cleaner production in 2015, while the panel data results indicate that the effect of cleaner production support by CPC on cleaner production practices diminished once the support came to an end. The other main factor is firm size, which indicates the financial position of the firm; international and regulator pressures are major determinants of the adoption of cleaner production measures. The analysis also indicates that there is higher probability of large firms adopting a cleaner production in comparison with small ones. Export orientation of firms is another important determinant of cleaner production. The enforcement of the environment compliance laws also has positive effect. The compliance with cleaner production measures is quite low, at 6.4 out of 19 cleaner production practice measures. There is a need to adopt measures that are environmentally friendly and are favorable towards both labor health and product quality, which are important for the sustainable growth of the tanning industry.

Possible use of corn starch as tanning agent in leather industry: Controlled (gradual) degradation by H2O2.

High molecular weight/size and poor solubility of native starch seems to be preliminary drawbacks in its possible use in leather processing as a tanning/retanning agent. For this purpose, firstly the native starch which has too large molecular size to penetrate between skin fiber matrix was oxidized with H2O2 in different molar ratios for disintegrating into appropriate molecular size that can be used in tanning process. Then, the product yields, water solubilities and degree of substitutions of oxidized starches were determined. Also, the oxidized starch samples were characterized by Fourier Transforms Infrared (FT-IR) Spectroscopy, Gel Permeation Chromatography (GPC) and Proton Nuclear Magnetic Resonance (1H NMR) Spectroscopy. According to the GPC results, the oxidized starch samples which their molecular weights were reduced for penetrating into skin fibers were selected and they were used in tanning process of goat skins. The tanning effects of selected oxidized starches were evaluated according to shrinkage temperatures, filling coefficients and Scanning Electron Microscopy (SEM) analysis. From the results, it was revealed that the native corn starch can be oxidized with H2O2 in a controlled manner and oxidized starch can be utilized as a tanning/retanning agent in leather making.

Studies on the use of sodium polyacrylate (SPA) for low-salt animal skin preservation.

Salt-based preservation is practiced for decades in the leather industry because of its versatility, cost-effectiveness, and availability. The salt removed from the soaking process causes significant pollution including organic and elevated total dissolved solids (TDS). Hence, a low-salt skin preservation method using commercial sodium polyacrylate with a reduced quantity of sodium chloride aiming to retain leather properties and pollution reduction was the principal focus of the study. Commercial sodium polyacrylate initially characterized for water absorption capacity along with structural and functional properties is confirmed by NMR and IR spectroscopic techniques. In preliminary experiments, the process parameters attained optimized conditions of sodium polyacrylate (SPA) quantity (5%), a minimal amount of salt (15%), and contact time (4 h) required for skin preservation. Besides, reusability studies after SPA recovery (95%) were applied to skins with an optimized quantity of SPA and salt subsequently stored for 15 days along with control (40% salt). The results revealed that SPA with low salt aided an adequate curing efficiency with a substantial reduction (> 65%) of TDS and comparable physical and organoleptic properties on par with the conventional method. Overall, SPA supported low-salt skin preservation reduces pollutant load (TDS) caused due to using of 40% sodium chloride in the conventional curing process.