Enzymatic Processing of Leather

Introduction

Environmental pollution caused by different effluents generated during the processing/ manufacturing of leather is one of the serious problems the country is facing today. Due to the violation of pollution control norms set by the Indian Government, some of the tanneries are forced to close down rendering people jobless and resulting in the loss of valuable foreign exchange to the country. Biotechnology, particularly the use of enzymes offer an opportunity to add value by providing improved cleaner processes for leather production and enhanced environmental management in the industry.

Currently, the most commonly used biotechnology applications cover all the stages of leather making processes and treatment of waste. An emerging technology is the use of proteolytic enzymes in unhairing process, which minimizes/replaces the use of sulphide, a major pollutant in the tannery.

In search of an eco-friendly, cost effective depilant for the unhairing process alkaline proteases was produced by isolating some microbes Aspergillus species from the local soil of IIT-Kharagpur has been evaluated for its efficacy. The activity and the performance of the enzyme have satisfied the conditions necessary for its application as depilant. The physical testing data (tensile strength, percent elongation and tearing strength) of the skins unhaired by enzymatic and chemical treatments were compared to evaluate the strength properties of the leather. The enzymatically treated leather was found to be superior to the leather obtained through chemical treatment. The comparison of microscopical structure of enzyme treated and lime sulphide treated pelts showed that the enzyme removes the intact hair which can be collected and used further.

Sl. No	Sample	Tensile strength (kg/cm 2 )	Elongation (%)	Tearing strength (kg/cm)
1	Lime sulphide goat (belly)	413.10	32.37	43.00
2	Enzyme treated goat (belly)	621.18	42.10	65.00
3	Lime sulphide goat (back bone)	335.58	3.87	34.00
4	Enzyme treated goat (back bone)	428.40	64.363	58.00

These results prove that enzymatic unhairing can be an excellent alternative to the age old chemical process as the trend is more towards cleaner technology and eco-friendly environment.

At IIT Kharagpur semi-pilot scale production and the application of the enzyme have been successfully carried out on different types of pelt. The process is found to be techno-economically viable one and the salient features of the indigenously developed product are given below.

Product Description:

• By enzymatic unhairing process, sulphide can be replaced totally, which are toxic in nature.
• No health hazard, worker can use this enzyme even in bare hand.
• Produced improved quality leather.
• % elongation, tensile strength, stitch tear strength also improves.
• For the manufacture of leather, unhairing is the first and most important step.
• Till date the conventional practice is to use sodium sulphide as depilatory agent.
• Among the disadvantages of the use of these chemicals is environmental pollution, health hazard.
• Enzymatic process of unhairing is considered to be the best and efficient alternative to the conventional lime-sulphide method.

Salient Features:

• Eco-friendly process
• Additional leather area (5%-10%)
• Cost saving on sulphide
• Hair recovery from goat and sheep skin
• Work in room temperature condition
• Required less amount of water during washing step so dispose of waste water
• problem also solved
• Giving better result under drumming
• Residual biomass after enzyme extraction can be used for biofuel production
• Unhairing could be accomplished in 5-7 hrs
• Better quality leather fetching higher price

Suggested minimum plant capacity:

300 MT per annum

Likely investment:

~ Rs.1.5 Crores

Production cost using Enzyme:

~ Rs 30-40/kg (Compared to conventional production cost: Rs.34/kg using sulphide (Rs.28/kg) & lime (Rs.6.00/kg)
Indian Patent has been obtained on this technology.

Contact for more information:

Prof. R. Banerjee
Microbial Biotechnology & Downstream Processing Laboratory
Agricultural & Food Engineering Department
Indian Institute of Technology
Kharagpur - 721 302
Phone Number: +91-3222-283104(O)/283105(R)
Email: rb@iitkgp.ac.in , rin_tuin@yahoo.com