Cellulase immobilized on kaolin as a potential approach to improve the quality of knitted fabric.

Biopolishing is a textile process that uses cellulases to improve the pilling resistance of fabrics. Although the process improves the pilling resistance, softness and color brightness of fabrics, it causes a significant loss of tensile strength in treated fabrics. The present work studied the use of cellulase immobilized on kaolin by adsorption and covalent bonding in biopolishing to get around this problem. The cellulase immobilization has been reported as promising alternative to overcome the inconvenient of biopolishing, but it has been very poorly explored. The results showed that cellulase immobilized by both covalent bonding and adsorption methods provided to the knitted fabric similar or superior pilling resistance to free cellulase, but with greater tensile strength. Immobilization also allowed for efficient recovery and reuse of the enzyme. The present work is a relevant contribution to the literature, since, as far as we know, it is the first work that shows it is possible to minimize the loss of tensile strength and also reuse the immobilized enzyme, giving a better-quality product and also contribution to reducing the cost of the polishing step.

Immobilization of endoglucanase on kaolin by adsorption and covalent bonding.

In the current research, endoglucanase, one of the enzymes of the cellulolytic complex, was immobilized on kaolin by two different techniques, adsorption, and covalent bonding. A comparative study was conducted between free, adsorbed, and covalently immobilized endoglucanase. For the covalent bonding, the kaolin particles were functionalized with 3-aminopropyltriethoxysilane (APTES) and activated with glutaraldehyde. Immobilization by adsorption was performed using the kaolin without any treatment. Recovered activities after the endoglucanase immobilization by adsorption and covalent bonding were found to be 60 ± 2.5 and 65 ± 3.5%, respectively. The studies of optima pH and temperature, as well as thermal stability, showed that the catalytic characteristic of the enzyme was maintained after the immobilization by both adsorption and covalent bonding. Even after 8 cycles of use, the endoglucanase immobilized by the two techniques retained about 86% of its initial activity. The results showed that the adsorption was as effective as covalent bonding for the immobilization of endoglucanase on kaolin. However, the adsorption technique seems to have a greater potential for use in future studies, as it is simpler, cheaper, and faster than covalent immobilization. Therefore, in this work it was demonstrated that endoglucanases can be immobilized efficiently on kaolin through a very simple immobilization protocol, offering a promising strategy for performing repeated enzymatic hydrolysis reactions.

Functionalized kaolin as support for endoglucanase immobilization.

Endoglucanases are an enzyme of cellulases complex that has a great potential for many technological applications. One of the issues of its use concerns the recovery and reuse of this enzyme. Thus, in this study, the use of a surface-modified kaolin was evaluated to immobilize endoglucanase and evaluate the enzyme activity for its reuse. Kaolin was surface modified with 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde (GA). In addition, the properties of the immobilized enzyme were investigated and compared with those of the free enzyme. Results showed that the optimal pH value of endoglucanase was not affected by the immobilization process but showed a broader range of optimal temperature compared to free enzyme. Immobilization on kaolin allowed fast and easy cellulase recovery with a loss of enzyme activity of only 20% after eight cycles of use. These results indicate that kaolin is a promising substitute to the currently synthetic supports studied for cellulases immobilization with the advantage of being abundant in nature, resistant to microbial attack, chemically and mechanically stable.