Applications of enzymes in leather processing

Abstract

The leather industry earns special attention because of its strong potential for foreign exchange earnings and employment generation prospects. This industry has developed enormously over the past decades; since, leather has become a material of choice in the world of fashion. However, this industry, like many others, is facing stringent environmental regulations worldwide, due to vast usage of toxic chemicals and generation of hazardous waste. Leather manufacturing involves conversion of raw skins and hides into leather through a series of mechanical and chemical operations. Processes like pre-tanning and tanning are known to contribute ~ 80–90% of the total pollution load in tanneries. In order to mitigate the hazards caused by toxic chemicals, enzymes have been identified as a practical alternative for use during processing and as well as for waste management. Even though the use of enzymes in the leather industry dates long back mainly because of their activity on proteins and fat, the complete replacement of chemicals by enzymes has yet to be realized. Earlier, enzymes were derived from animal excreta, and later on from the pancreas of cattle. However, currently, the enzymes are almost entirely produced by microbial fermentation. In light of this, the current review presents a holistic view on the effective utilization of enzymes in leather making, mainly during soaking, dehairing, bating and degreasing processes in order to minimize waste generation, and also in the recovery of valuable and saleable by-products. Globally, ~ 7 million tons of salted bovine hides are used every year for leather making. By using enzymes in bio-preparation, around 8 million gigajoules of energy saving and 0.7 million tons of CO2 savings is estimated to be achieved due to lower processing times and associated energy use. Nevertheless, the search for enzymes for their ultimate application in the leather industry as an eco-friendly alternative continues, since, this process is far safer and more pleasant than the traditional method. The progress made in this field during the past two decades are highlighted and will provide further insight on the scope for utilization of enzymes in this industry. In order to achieve sustainability, clean environment and prevent health hazards, the leather industry ought to adopt the use of eco-friendly alternatives which might primarily depend on research, development and implementation of the potential enzyme technology.