Unhairing of bovine skin with fungal enzymes by immersion and spread throughout the epidermis

Abstract

The use of enzymes during unhairing in the leather industry to partially reduce sulfide can decrease H2S emission to almost 50%. However the proteolysis needs to be controlled to prevent collagen damage. In bovine epidermis, the stratum corneum plays a crucial role as a hydrophobic barrier. In order to facilitate the diffusion of enzymes, it is necessary to generate channels through this barrier to allow enzymes pass without damaging the collagen. In an ideal enzymatic unhairing the proteolytic activity should be restricted to the basal lamina and pilosebaceous unit. During this experiment, fungal enzyme extracts (CE) were applied on bovine skin in the soaking and unhairing steps as part of the tanning process. The skin contacted with the solutions in two different ways: in direct contact with the epidermis (Mode I) and immersed in the solution (Mode II). Various keratinolytic fungi, previously isolated and selected from different soil samples were used: Neurospora crassa, Verticillium albo-atrum, Trichophyton ajelloi, Chrysosporium sp, Aspergillus sydowii, Paecilomyces lilacinus and Acremonium murorum. The fungal isolates were cultivated under solid state conditions using hair waste obtained from the hair-saving unhairing process as substrate. Enzyme extracts were characterized according to their keratinolytic and proteolytic activity and protein content. Once the immersion with fungal enzymes was finished, the treatment with N. crassa, T. ajelloi, Chrysosporium sp, A. sydowii and P. lilacinus, showed unhaired skin and epidermis removed. After the contact between the epidermis and fungal enzymatic extract of T. ajelloi empty hair follicles were observed. The morphological changes were studied with SEM (Scanning Electron Microscopy).