Enzyme mediated beam house operations of leather industry: a needed step towards greener technology

Leather industries, due to pollution of water, careless disposal of solid wastes and gaseous emissions, are categorized as a red industry and are under deep pressure to develop environmentally efficient leather-making processes to comply with modern pollution and discharge legislation. In the present study, completely enzyme based beam house operations (dehairing & degreasing) of leather industry has been standardized for skins & hides using Bacillus licheniformis protease and Bacillus subtilis lipase. Owing to its immense importance and demand the productions of these enzymes were optimized and scaled up in a 300 L bioreactor resulting in a maximum yield of 4568 U/mL in 18 h for protease and 34.91 IU/mL of lipase in 36 h. 100% enzymatic dehairing & degreasing of skins and hides could be obtained at pH value of 8.0 and temperature 30–37 °C with the enzyme concentration of 2–5% (w/v) of protease for dehairing and 5–10% (w/v) of lipase for degreasing within 8–12 h. An interesting observation noted for enzyme based leather processing was that natural skin colour was preserved along with a drastic reduction of BOD and COD values of effluent. Crust leather formed using enzymatically processed skins exhibited similar physical and tactile properties as observed for conventional crust leather. On the bases of internally quenched fluorescent substrate specific method, this protease is subtilisin-like serine protease with low collagenase activity. High collagenase activity can damage the hide (leather) grain and the physical-mechanical characteristics of the hides. Successful demonstrations of large size (Industrial trials −100 kg skin/hide at Central Leather Research Institute, Chennai, India) 100% chemical free dehairing and degreasing further supports the authenticity of the work. Thus all this makes the beam house operations of leather tannery enzymatically feasible and environmentally benign.