Ecofriendly lime and sulfide free enzymatic dehairing of skins and hides using a bacterial alkaline protease

• Published in: Chemosphere (Oxford) 2008, Vol.70 (6), p.1015-1024
• Main Authors: Sivasubramanian, S., Murali Manohar, B., Rajaram, A., Puvanakrishnan, R.
• Format: Article
• Language: English
• Subjects: alkaline proteinases; Animals; Applied sciences; Bacteria; Bacterial Proteins - metabolism; Biochemical oxygen demand; Calcium Compounds - chemistry; Cattle; Chromatography, High Pressure Liquid; Collagen; dehairing; Endopeptidases - metabolism; enzymatic treatment; enzyme activity; Exact sciences and technology; Goats; Hair Removal - methods; hairs; hides and skins; Industrial wastewaters; Leather; Liming; Microscopy, Electron, Scanning; Other techniques and industries; Oxides - chemistry; Pollution; Protease; proteinases; Proteoglycan; proteolysis; Skin - chemistry; Skin - metabolism; Skin - ultrastructure; Sulfides - chemistry; Tanning - methods; Wastewaters; Water Pollution, Chemical - prevention & control; Water treatment and pollution
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2007.09.036

The ever-increasing attention to the environmental impact of leather industry has necessitated the development of enzyme-based processes as potent alternatives to pollution causing chemicals. In this study, a hair saving process is developed for dehairing of skins and hides using a bacterial alkaline protease preparation, completely eliminating the use of lime and sulfide. To evaluate the efficacy of the enzymatic process, comparative studies have been carried out with two controls; a conventional lime–sulfide process and enzyme-assisted process using commercial dehairing enzyme with reduced quantities of lime and sulfide. The developed process requires a shorter duration of 6 h for complete dehairing of skins and hides than control groups and also, it avoids the use of silicate carriers since the enzymatic dehairing is carried out by dip method. Histological and scanning electron microscopic analyses of the dehaired pelts obtained from enzymatic process reveal complete removal of hair and epidermis with moderate opening up of fiber structure in both dermis and corium. Moreover, the collagen is not damaged and resulting in a leather of good quality. The developed process has resulted in a remarkable reduction of effluent load in terms of biochemical oxygen demand, chemical oxygen demand, total dissolved solids and total suspended solids. Physicochemical studies conclusively show that the leathers produced by enzymatic process are equivalent to or better than that obtained by control systems. Thus, the developed enzymatic process offers immense potential for greener mode of dehairing of skins and hides in leather industry coupled with environmental excellence.