Enzyme based fibre opening

10 July 2008

SPIC Biotechnology, based in Chennai, specialise in enzyme-based products for the leather industry. With ‘Spic Bio Dart' they offer a complete package of beamhouse products.

Abhay Kumar, manager, stated: ‘This is a new chemical product which replaces toxic beamhouse chemicals by up to 95%. The ‘fibre opening enzyme' has been developed over the last eighteen months in conjunction with the CLRI. Its purpose is to reduce the pollutant load and reduce the need for water treatment which implies a cost saving in the long term. The enzyme is suitable for soaking, de-hairing, bating and anti-wrinkling. According to SPIC, the soaking, liming, reliming, deliming, bating, pickling, chrome tanning and basification or vegetable tanning and fixing, account for nearly 90% of total pollution from a tannery. This is primarily due to the fact that conventional methods employed in leather-processing subject the hide or skin to wide variations in pH. Such pH changes demand the usage of acids and alkalis, which leads to the generation of salts and toxic gases such as ammonia and hydrogen sulfide. In addition, a great deal of solid waste such as lime sludge from the tannery and chrome sludge from effluent treatment plant are generated. Liming and reliming has been a particularly problematic area as they contribute 60-70% of the total pollution load in leather processing. The conventional unhairing process with sodium sulfide and lime is responsible for 84% of BOD5, 75% of the COD, 92% of suspended solids and 100% of the toxicity of the total pollution from a tannery. Lime has the potential to promote gradual swelling due to its low solubility, but formation of a large amount of lime sludge is a major drawback. Extensive use of sodium sulfide bears unfavourable consequences for the environment and the efficacy of ETPs. The use of ammonium salts for deliming leads to the emission of toxic gas (ammonia). Salt is used in pickling to suppress acid swelling, but contributes to TDS.  Commercial chrome tanning results in just 50-70% chromium uptake which results in waste and ecological imbalances. According to SPIC, this calls for the evolution of integrated process technologies by rethinking the process sequence as shown in Figure 1. This can be achieved via ‘Do-Only process logic' where each process performs a specific action without any need for reversing the performed action. The methodology based on biomediated dehairing, fibre opening (swelling) and pickle-free chrome or vegetable tanning through a narrow pH profile would lead to near zero discharge of pollutants and wastewater.  A biotechnological pathway without lime forms a ‘green' route for dehairing and fibre opening. Dehairing using commercially available enzyme formulation, with or without sodium sulfide, has been designed for both hides and skins at an operational pH of 8.0-8.5. Hence, this method uses enzymatic treatments that are capable of splitting fibres at a pH of 8.0 alongside enzymatic dehairing, thus providing an opportunity to avoid deliming. SPIC claim that enzyme-based fibre opening is a paradigm shift away from conventional chemical-based leather processing to bio-processing. Lime-based swelling removes interfibrillary materials through osmotic forces leading to a reduction in area and wrinkle formation. On the other hand, substrate-specific enzymes disintegrate the proteoglycans making the fibre matrix open, thereby inducing swelling. This approach obtains a clean pelt with the desired fibre opening and a significant reduction in lime sludge. Enzyme based de-hairing and fibre opening also improves area yield and reduces wrinkle formation. Further advantages include reduced levels of TDS, chlorides and BOD in the waste tanning solution. Integration of these methods provides a three-step tanning process facilitating zero discharge leather processing. Mitozyme FL is a versatile enzyme preparation for use after depickling or chrome tanning, developed exclusively to reduce wrinkles and growth marks. It imparts appreciable softness and smoothness to the leather and improves uniformity of colour and fineness of grain with maximum stretch but no loosening of flanks. Biodart Biograin effectively attacks the outermost sheath of the hair bulb resulting in depilation, thereby producing flat leather without wrinkles and growth marks. Quality of hair recovered is superior compared to conventional process. Wrinkle Resist 3X effectively attacks the outermost sheath of the hair bulb resulting in better depilation and produces flat leather without wrinkles and growth marks.  Biodart Soll 90 induces uniform soaking and facilitates the removal of dirt, bloodstains, glycoproteins and lypoproteins. Biodart Acbate is a versatile enzyme formulation which imparts appreciable softness to the leather. Biodart Albate and Albate - EX are versatile enzyme formulations which help open up collagen fibres, clean up scuds and impart a smooth, silky and flaccid pelt. Bio Soft - SG is a multi-faceted enzyme preparation to open up the fibre structure of wet-blues and imparts silky smooth grain. It helps in removing fold marks of pickled pelt also. Spic are a large Indian bio-tech group operating for the last twelve years. They have an annual turnover of US$1 billion.

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