Kraft lignin degradation products for tanning and dyeing of leather

Kraft lignin degradation by a biomimetic system was investigated, using hemin as a catalyst and hydrogen peroxide as an oxidising agent, which mimics the catalytic mechanism of lignin peroxidase (LiP) to produce phenolic compounds. The degradation products were identified using spectroscopy and gas chromatography-mass spectrometry (GC-MS): 2-methoxyphenol, 4-hydroxybenzaldehyde, vanillin and vanillic acid were produced and their formaldehyde polymerisation products used for tanning hide powders. The denaturation (shrinkage) temperature of hide powder was raised to 80 degreesC through hydrogen-bonding interactions between the polymers and the collagenic hide powder. For dyeing of hide powder, the lignin degradation products were reacted with laccase (a polyphenol oxidase): 2-methoxyphenol gave the darkest colour. These products have potential to be used as raw materials for tanning and dyeing of animal skins. Therefore, value can be added to this industrial byproduct and reduce its environmental impact. (C) 2004 Society of Chemical Industry.