|Anandan, Dayanandan - FORMER VISITING SCIENTIST|
Submitted to: Journal of American Leather Chemists Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 20, 2008
Publication Date: October 1, 2008
Citation: Anandan, D., Marmer, W.N., Dudley, R.L. 2008. Enzymatic Dehairing of Cattlehide with an Alkaline Protease Isolated from Aspergillus tamarii. Journal of American Leather Chemists Association. 103(10):338-344. Interpretive Summary: Tanners want a safer and more environmentally sound method for the removal of hair from animal hides than the traditional method, which uses toxic sodium sulfide. Enzymatic dehairing has great potential in this regard. We earlier had successfully demonstrated that it is possible to obtain large quantities of an alkaline protease enzyme from a common fungi, Aspergillus tamarii. We now have applied that enzyme to dehairing cattlehide and we then converted the dehaired hide to leather. The quality of the leather produced from the enzymatically dehaired hides was similar to the quality of leather produced from hides dehaired with sodium sulfide. The only observed drawback was the inability to remove the fine hairs from the hide. We therefore developed a subsequent dehairing step, based on peroxide, to remove that residual hair. The new two-step process reduces the amount of chemicals in the tannery waste stream and eliminates sulfide. The achievement of effective and safe dehairing, with concomitant reduction in the cost of remediation of the tannery waste stream, increases the ability of tanneries to compete in a world market.
Technical Abstract: An enzymatic dehairing protocol based on the alkaline serine protease isolated from Aspergillus tamarii required 16h, and we observed concomitant grain damage. The use of sodium dodecyl sulfate as a pretreatment to remove the lipids from the hide allowed a shortening of the dehairing time to 6 h without grain damage. We postulated that the SDS removed all of the sebaceous grease from the pores of the hair, facilitating the penetration of the enzyme through the grain layer. Using a lypophilic dye, Nile red, we showed that SDS did remove some of the grease from the grain side of the hide. By tagging the enzyme with a fluorescent label we clearly showed, however, that the enzyme penetrated the hide only through its flesh side. The enzymatic dehairing process did not remove the fine hairs from the hide. Adding a common sharpening agent, sodium sulfide, to the liming step removed the fine hairs but also caused grain damage. Employing an oxidative ‘liming’ step, based on alkaline sodium percarbonate, did remove the fine hairs; under carefully controlled conditions, grain damage was not observed. Mechanical data were collected from leather prepared from enzymatically dehaired hide that had been limed, enzymatically dehaired hide that had been oxidatively 'limed' and hide that had been dehaired with sulfide and relimed. The tensile strength of the leather made from enzymatically dehaired oxidatively relimed hide was significantly stronger than the leather prepared from the enzymatically dehaired and 'traditionally relimed hide.' The tensile strength of the leather produced from the sulfide control was intermediate.