Enzymatic removal of dung from cattle hides

One of the major problems facing the meat and leather industries is dung cladding on hides. Dung dried onto hides is difficult to remove during the early stages of processing, resulting in the necessity for prolonging the soaking step, with the consequence of risking bacterial damage to the hides. Microscopic examination of dung on hide reveals that adhesion is between the dung and the hair alone, with no sticking of the dung to the epidermis. This accounts for the difficulty in removing dry dung; the matrix of the hair within the dung creates a strong composite material. Analysis shows that major components of the composition of dung are lignocellulosic materials (lignin, hemicellulose and cellulose). This project concerns solubilising the dung faster, to reduce soaking time by targeting these components with enzyme technology, using hemicellulases, cellulases, and laccases from commercial products and a range of fungal organisms (Coriolus versicolor and Aspergillus niger). Removal of dung from hide pieces is affected by the action of cellulase, xylanase and laccase separately over 20-24 hours. Mixture of these enzymes removes dung in 6-8 hours demonstrating that synergistic activity is more effective than separate enzyme treatments. When commercial enzyme mixture or Coriolus versicolor or Aspergillus niger cultural broths were used to effect dung removal in tannery drums in a larger scale experiment, in some cases the removal of dung was observed within 1 hour by the help of the mechanical action and nonionic surfactant. The enzyme treatment did not affect the components of hide, such as collagen, hyaluronic acid and dermatan sulphate and it was found that enzyme treated leathers and control samples showed no differences in terms of their physical characteristics. Investigations in the mechanism of dung removal by spectrophotometry, chromatography and chemical techniques show that the enzyme treatments remove the dung from hides without changing the fundamental structure of the substrate. The enzymes probably attack the structural parts in lignocellulose, which are most susceptible to solubilising with enzymes: these attacks make small changes in the carbohydrate and lignin contents, but these changes are powerful enough for effective dung removal