Influence of Enzyme and Mordant Treatments on the Antimicrobial Efficacy of Natural Dyes on Wool Materials

摘要

Some of the natural dyes containing tannin as their major chemical constituent can be used to impart antimicrobial efficacy to wool fabrics in addition to dyeing. The treatment with mordant is inevitable during natural dyeing process in order to improve the fastness properties as well as to produce different shades on wool fabrics. Similarly, wool fabrics are subjected to protease enzyme treatment to increase the uptake of dye. In this study, it was attempted to study the effect of such enzyme and mordant treatments on the antimicrobial efficacy of the wool fabrics dyed with selected natural dyes. Wool fabrics were treated with four natural dyes having in vitro antimicrobial efficacy to both gram positive and gram negative bacteria with and without the use of enzyme and mordants. The test results showed that the antimicrobial efficacy of dyed wool samples was significantly influenced by enzyme and mordant treatments. The control dyed fabrics showed antimicrobial efficacy only against gram positive S. aureus bacteria whereas the enzyme treated fabrics had antimicrobial efficacy against both S. aureus and gram negative E. coli bacteria. This may be due to 17% higher dye uptake in the enzyme treated materials. The mordant treated wool fabrics generally showed less antimicrobial efficacy against S. aureus compared to control dyed fabrics. None of the mordanted materials had shown antimicrobial efficacy against E. coli even with enzyme pretreatment. The complex formation between the mordants and active constituents of tannins present in the dyes may be the reason for less or nil antimicrobial efficacies in those wool fabrics.