Enzymatic Removal Of Non-cellulose Impurities On Cotton Fabric And Its Application In Textile Process

Bio-scouirng is an ideal alternative and more environmentally friendly method to remove the non-cellulosic impurities from raw cotton by specific enzymes to make the surface more hydrophilic. However, bio-scouirng is not as effective as alkaline scouring in removing the non-cellulosic impurities, especially in removing cotton seed coat fragments (CSF), which has become the largest obstacle to the commercialization of cotton bio-scouring.To enhance the removal of CSF in cotton bio-scouring, enzymes which can greatly degrade cotton seed coat were secreted based on cotton seed coat structure and chemical composition analysis. And then the mechanism of the biodegradation of cotton seed coat by those enzymes and their synergistic effects were studied. Furthermore, the key reason for effective enzymatic catalysis in cotton bio-scouring process and its mechanism were presented. Moreover, a novel strategy to scour and bleach cotton at low temperature in a single bath to improve the removal of SCF was achieved. The main contents of this dissertation are as follows:1. The chemical composition and structure of cotton seed coat were investigated by using Fourier Transform Infrared (FT-IR) Microspectroscopy technology. Based on these results enzymes which can greatly degrade cotton seed coat were choosed. These enzymes were alkaline xylanase, fungal cutinase, alkaline cellulase and alkaline pectinase. The optimum concentrations for them were studied and 10.66% of CSF removal was achieved, compared with 40.33% of that in traditional scouring process, and 4.7% and 8.6% of that in cotton bio-scouring with other two commercial enzymes for scouring.2. Cutin in cotton seed coat epidermal layer can be degraded by cutinase. After treated with cutinase, the relative adsorption capacity of cotton seed coat for alkaline xylanase was improved by 1.28 fold. And a synergism was obtained on the degradation of cotton seed coat when combined cutinase with alkaline xylanase or alkaline pctinase. As a result, the reducing sugars produced in the treatment bath increased by 800μg and 1270μg for alkaline xylanse and alkaline pectinase, respectively. Whereas, the weight loss of cotton seed coat increased by 7% and 8% for alkaline xylanase and alkaline pectinase, respectively.3. Temperature has a great effect on the degradation of cotton seed coat by alkaline xylanase, and it was considered as a great factor to affect the effective enzymatic catalysis in cotton bio-scouring. The best description of the degradation of cotton seed coat by alkaline xylanase was achieved as . Based on that, the rate (v) of the degradation of cotton seed coat can be calculated for differentα. The results indicated that the rate (v) was greatly higher at 55°C and 65°C) than that of at 30°C and 45°C. Moreover, temperature has same effects on the removal of waxes, pectin and CSF with increasing treatment temperature in cotton bio-scouring for cutinase, alkaline pectinase and alkaline cellulase. Therefore, with in a certain scope of treatment temperature, the effectiveness of these enzymes used in the experiment increased with increasing treatment temperature.4. The effectiveness of enzymatic catalysis has a close relationship with the removal of waxes from cotton fabric. With a increasing temperature more waxes will be melted and released from the fabric, which results in increased active site for enzymes, and finally more enzymes protein was adsorbed onto the cotton fabric. These maybe the possible important reasons for an increased effectiveness results of different enzymes in cotton bio-scouring. Based on above results, a temperature control strategy was developed to enhance cotton waxes removal. With this strategy, the removal of cotton waxes, pectin and CSF was increased to 75.37%, 85.33% and 14.87%, compared with that of 59.83%, 79.8% and 10.66% of the control, in which cotton fabric was treated in the same conditions except that the temperature was always kept at 55°C.5. Based on the bleaching characteristic of H₂O₂, a novel strategy was developed to scour and bleach cotton in a single bath at a lower temperature. In this process, tetraacetylethylenediamine (TAED) was used as an activator for H₂O₂ to bleach cotton fabric at the temperature for cotton bio-scouring after the cotton scoured with enzymes and H₂O₂ in the same bath. The results indicated that H₂O₂/TAED system can effectively improve the removal of non-cellulosic impurities, especially in the removal of CSF after the scouring process. After cotton fabric scoured with enzymes and H₂O₂, the removal of CSF increased by 25.13%, compare with that of the normal bio-scouring process. After cotton fabric was scoured and bleached with H₂O₂/TAED system, the removal of waxes, pectin and SCF were 92.27%, 87.35% and 88.06%, compare with 95.66%, 89.57% and 90.33% of the traditional alkaline scouring and bleaching process.