Biomimicking of Enzymes for Textile Processing

Abstract

Enzymes are very large protein compounds. A small portion of their structure constitutes their highly specific active site which is fundamentally responsible for the catalytic capability of the enzymes. To mimic the active site of different oxidoreductases the components of the active site of were studied regarding their functionality when isolated without the complete protein structure. Oxidoreductases investigated include glucose oxidases, peroxidases, and laccase. Glucose oxidases belong to oxidoreductase enzymes and are capable of generating hydrogen peroxide for bleaching of cellulosic textile materials and pulp fibers. Their active site contains flavin adenine dinucleotide (FAD) as cofactor. Compounds similar to the active site were used to mimic the reactions of the intact enzyme. The mimics’ dosage, pH value and the source of oxygen play a role for the reaction to occur as well as the exposure to light. The influence of amino acids that are in direct contact with the cofactor of the intact enzyme on the biomimetic reactions was also explored. The mimics of glucose oxidase applied for bleaching cotton fabric could achieve whiteness levels of about 70% compared to whiteness levels reached with glucose oxidase or commercial H2O2. Lignin and manganese peroxidase and laccase are enzymes that are not capable of generating peroxide, however have proved to play important roles in the degradation of ligninic compounds in pulp. The application of these oxidoreductases to unbleached linen was investigated regarding their bleaching effectiveness. Glucose oxidase can also be used for bleaching of linen. Laccase was found effective for delignification of linen fibers to increase the whiteness of linen fabric. The combination of laccase and glucose oxidase for bleaching of linen fabric showed higher effectiveness regarding whiteness than either one of the enzymes applied alone. The whiteness increase of treated fabric might be related to the decrease of lignin content of enzyme-treated linen. The surface properties of scoured unbleached linen fibers and enzymatically treated linen fibers were investigated by inverse gas chromatography (IGC), and the dispersive component free energy as well as surface acidity constant (Ka) and basicity constant (Kb) were determined. The decrease of both Ka and Kb of enzymatically treated linen can be explained by the change of surface chemical groups of the linen fibers. For the linen fabric high in lignin weight the Ka and Kb values of enzyme-treated fabric are inconclusive and not directly related to the whiteness and lignin content of the fabric.