Biotechnological processes in leather making

BIOTECHNOLOGY PROCESSES IN LEATHER MAKING

Soaking

  • Soaking enzymes are used to shorten production time by attacking solidified fats and non-collagenous proteins that interpose themselves between the fibers. These proteins sometimes cover the external surfaces of the hide, making contact between collagen fibers and water difficult.
  • Rather than targeting a specific reaction, the enzymes used in soaking target a broad-spectrum of reactions to obtain both solubilization and removal of the interfibrillar proteins, enabling easy rehydration of the skin.
  • The types of enzyme used in the soaking of hides are carbohydrases and proteases.
  • The advantages of an enzyme soak include shorter wetting times, loosening of the SCUD, initiation of FIBER OPENING, and production of a product with a lesswrinkled grain. However, a major disadvantage of their use is the added costs involved.

Liming

  • The conventional process of liming uses high proportions of lime and sulfide. These materials are a source of pollution in the spent lime liquors. An advantage of using lime is that it is a poorly soluble alkali thus providing limited availability of dissolved alkalis. However, a disadvantage is that it generates large quantities of solid waste. Although sulfide is toxic, it is the prime depilant in the de-hairing process.
  • It is now possible to reduce sulfide at its source using enzyme-assisted processes. Enzymes used in de-hairing are generally proteolytic, catalyzing the breakdown of proteins. Their origin can be animal (e.g. from bovine or porcine pancreas), bacterial, fungal or plant. Enzymatic de-hairing generally uses proteolytic enzymes along with small amounts of sulfide and lime.
  • The mixture is painted onto the fleshside, causing the hair to be loosened by selective breakdown of the cementing substances in the hair follicle, thereby keeping the hairs intact.

Bathing

  • Bating is the process of removing proteins other than collagen using proteolytic enzymes. The most important function of the enzymatic bate is removal of the coagulable protein of skin.

Degreasing

  • The degreasing process is another stage of the tanning process where the use of enzymatic products is feasible. The degreasing process can be broken down into three successive stages:
    • breakdown of the proteic membrane of the fat-containing sac,
    • removal of the fat, and
    • emulsification of the fat in water or solubilization in solvent. An enzymatic preparation, therefore, needs a triple-action (proteolysis, lipolysis and emulsification) to be an effective degreasant.
Last modified: Tuesday, 15 May 2012, 7:56 AM