De hairing hide without polluting
A biodegradable enzyme that can replace two conventional agents now used to de-hair animal skins for leather manufacture has been produced by the Madras-based Central Leather Research Institute (CLRI). Christened Clarizyme, the enzyme is extracted from a fungus, Aspergillus sp. It has several advantages over the conventional agents, calcium oxide (lime) and sodium sulphide. The most important, of course, is that the enzyme is non-polluting.
Clarizyme dissolves the protein at the base of the hair root that holds it in the skin, so that the hair drops off. Lime and sodium sulphide, on the other hand, act only on the surface of the hide. Broken hairs then decay in the waste water from tanneries and increase its pollution potential.
To isolate Clarizyme, CLRI used the solid substrate fermentation method that allows extractions in high concentrations. It extracted the enzyme by fermenting the fungus grown on moistened wheat bran.
"This method," explained Malathi Srinivas of CLRI's department of biotechnology, "was very popular before the Second World War, but was later sidelined by the liquid fermentation method." Srinivas said the technology is easy to replicate and the raw material used is cheap. The shelf life of the enzyme under room temperature is around two months, she added.
The enzyme was tested at the test tannery on the CLRI campus and also at commercial tanneries in Dindigul and Vaniyambadi. The enzyme proved to be both effective and environmentally sound, but its cost was high, compared to that of the conventional de-hairing agents, especially as small tanners don't take pollution control costs into account.
CLRI is now trying to reduce costs so that entrepreneurs can take it up for commercial production.