Neutral Cellulase

The activity of any enzyme depends primarily on the pH and temperature of the reaction system. Basically, cellulases can be divided in to four basic groups according to the pH required for optimum enzymatic activity. One group is called Acid Cellulases because the pH ranges from 4.5 to 5.0. There are Hybrid Cellulases whose optimum pH is 4.5 to 7.0. The third group called the Neutral Cellulases is active from a pH 6.0 to 8.0 but is optimal at pH 6.2. The fourth group is commonly reffered as to Alkaline Cellulase enzymes because its optimum pH is 7.2 to 8.5.

The major applications of Neutral Cellulase is for paper processing, on cotton and denim finishing. The use of the cellulase treatment to obtain the stonewash effect in denim finishing has attracted considerable interest in the last few years. The primary attraction towards the use of cellulase enzymes is to reduce or eliminate the need of stones, or to reduce the time needed to obtain the desired abrasion. Some style names used to refer to the use of cellulase include chemical wash, stoneless wash, enzyme wash, etc.

There are two categories of the enzymes, acid cellulase and neutral cellulase. The neutral enzyme gives less back staining. The latter property is responsible for a more reproducible finish from different washes.

The performance of the Acid Cellulase enzymes is charecterized by its highly aggressive action on cotton. However, acid cellulases are associated with backstaining, which may be undesirable and excessive strength loss. The action of the hybrid, neutral and alkaline cellulase enzymes towards cellulase is less aggressive and requires longer time cycles. They do, however, produce less backstaining.

Application:

Cellulase enzymes were initially promoted with the promise of completely eliminating stone as the abrasive agent in achieving the stone wash look. Using cellulase as a substitute for the pumice stones prevents the damage to washing machines and the garments, eliminates the disposal of the used stones, improves the quality of the waste water and eliminates the need for labour intensive removal of stones from the finished garments.

However, due to increased time and other considerations, the trend today is to use combinations of stone and cellulase to achieve the worn out look more quickly. Some highly abraded finishes cannot be achieved just by using cellulase alone. In such cases partial substitution of stones with the enzymes can achieve the desired look. Neutral cellulase works best at pH 6 however its activity is not adversely affected in the range of pH 6-8 and show maximum activity at 55°C.

The cellulase enzymes are used in washing. They act on the cotton yarn and thereby facilitate the abrasion of the indigo dye from the yarn surface. The cellulase hydrolyses cellulose, yielding soluble products such as short-chain polysaccharides and glucose. This action loosens the indigo layer, which is then more easily removed by mechanical abrasion. Use of cellulase overcomes most of the disadvantages of stones while yielding the desired softening and "worn" look.

Pulp fibrillation by cellulases was recognized as a means to enhance strength properties as early as 1959. Cellulases from the fungus Aspergillus niger were used to enhance fibrillation, thereby improving the strength of paper by increasing fiber-fiber contact. It was principally applied to cotton linters and other non-wood pulps. A process patented in 1968 used cellulases from the white-rot fungus Trametes suaveolens to reduce refining or beating time. Nomura reported that cellulase plus cellobiase added to pulps facilitated fibrillation without strength loss, have also described the use of cellulases to improve fibrillation of pulps.