Dehairing of animal hides and skins by alkaline proteases of Aspergillus oryzae for efficient processing to leather products in Tanzania

Abstract

The leather industry is one among the most vital sectors for economic development contributing to high earnings. However, tanning of hides and skins is constrained by primitive technology and the use of hazardous chemicals that contribute to environmental pollution. This study was conducted to evaluate the efficacy of alkaline protease on dehairing animal hides and skins under different conditions. Alkaline protease was extracted from Aspergillus oryzae MG429773 cultured by solid state fermentation with a medium containing rice husks supplemented with 1% mineral solution incubated at 30 to 35°C for 7 days at pHs ranging from 7.5 to 9.5. The filtrate was used as a crude enzyme solution and also partially purified for a dehairing bioassay. Four pieces of cattle hide and goat skin (10 cm × 10 cm) were soaked or sprayed with enzyme solutions for a maximum of 5 days. Percentages of depilation of the hides and skins were recorded at 6 and 12 h intervals. Enzyme produced by A. oryzae showed the highest dehairing activity from 15 to 20% concentration of partially purified enzyme whereby 100% of goat and cattle hairs were removed within 24 and 48 h, respectively. For 5 and 10% enzyme concentration, 93.75 and 68.75% of hide and skin depilated in 72 h, whereas for the control 0.0 to 6.5% depilation was achieved in 72 h in hide and skins, respectively. Application of the A. oryzae protease by spray method was superior over a dipping method that released hair in effluent and caused skin decay after 5 days of exposure. This study indicates that enzyme extracted from cheaply available resources is efficient for dehairing by a spray method could be a potential technology for application by local tanners to improve the leather industry in Tanzania.