Optimization of Enzymatic Degreasing of Sheep Leather for an Efficient Approach and Leather Quality Improvement Using Fractional Experimental Design.

Leather industry is making significant contributions to economic development. However, it is notably leading to a serious environmental pollution. Recently, the enzyme technology developments offer new opportunities for enzymatic application in leather making. In the present investigation, microbial lipases were studied and used in degreasing process of sheep leathers. In order to optimize degreasing efficiency, a fractional experimental design with four parameters (enzyme source, processing stage, lipase amount, and degreasing duration) was used. Lipases A from Aspergillus niger, F from Rhizopus oryzae, R from Penicillium roqueforti, and AY from Candida rugosa were selected for leather degreasing. Enzymatic treatment of sheep skin was carried out during two stages of beamhouse operations: deliming-bating and pickling. Obtained results showed that enzymatic degreasing efficiency is higher than those obtained with the conventional process. Lipase F from Rhizopus oryzae demonstrated the most interesting hydrolysis with yields of 58.3% and 37.2% for delimed and pickled skins, respectively. An enzymatic degreasing process on pickled leather using 0.125% (w/v) of lipase F during 3.5 h is the most promising for an industrial application with a 76.03 of degreasing efficiency. Results of the physico-mechanical tests of leathers having undergone enzymatic treatment complied with industry requirement. The enzymatic treatment may be carried out in the same conditions as employed in leather manufacturing process. Results suggested that the enzymatic degreasing improves the leather quality and reduces the use of chemical compounds and surfactant.

Cleaner degreasing of sheepskins by the Yarrowia lipolytica LIP2 lipase as a chemical-free alternative in the leather industry.

Conventional degreasing of skins and hides in the leather industry requires high amounts of organic solvents and detergents that cause environmental issues. In this study, the LIP2 lipase from the yeast Yarrowia lipolytica (YLLIP2) was shown to be effective in degreasing sheepskins, thus reducing the amount of harmful chemicals. Using 6 mg of lipase/kg of raw skin, successful degreasing was achieved in only 15 min at pH 8 and 30°C. ToF-SIMS mass spectra of chemically and enzymatically treated sheepskins are consistent with a selective elimination process for the enzymatic treatment. Comparative SEM microscopy, ATR-FTIR spectroscopy and physicochemical analyses showed better properties of the enzymatically treated leather than those of the chemical treatment. Effluent physicochemical parameters showed that the enzymatic treatment is a cleaner degreasing operation. Altogether, this work opens new horizons to use the YLLIP2 lipase as a more efficient alternative in the leather industry.

Heterologous expression and purification of keratinase from Actinomadura viridilutea DZ50: feather biodegradation and animal hide dehairing bioprocesses.

The keratin-degrading bacterium Actinomadura viridilutea DZ50 secretes a keratinase (KERDZ) with potential industrial interest. Here, the kerDZ gene was extracellularly expressed in Escherichia coli BL21(DE3)pLysS using pTrc99A vector. The recombinant enzyme (rKERDZ) was purified and biochemically characterized. Results showed that the native and recombinant keratinases have similar biochemical characteristics. The conventional dehairing with lime and sodium sulfide degrades the hair to the extent that it cannot be recovered. Thus, these chemical processes become a major contributor to wastewater problem and create a lot of environmental concern. The complete dehairing was achieved with 2000 U/mL rKERDZ for 10 h at 40 °C. In fact, keratinase assisted dehairing entirely degraded chicken feather (45 mg) and removed wool/hair from rabbit, sheep, goat, or bovine' hides (1.6 kg) while preserving the collagen structure. The enzymatic process is the eco-friendly option that reduces biological (BOD) (50%) and chemical (COD) oxygen demands (60%) in leather processing. Consequently, the enzymatic hair removal process could solve the problem of post-treatments encountering the traditional leather processing. The enzymatic (rKERDZ) dehaired leather was analyzed by scanning electron microscopic (SEM) studies, which revealed similar fiber orientation and compactness compared with control sample. Those properties support that the rKERDZ enzyme-mediated process is greener to some extent than the traditional one.