What is the working principle of commonly used enzymes in pretreatment?

The mechanism of action of pectinase: pectinase is divided into ordinary pectinase, protopectinase (PPASe), alkaline pectinase and so on. The commonly used pectinase is a complex enzyme that can effectively degrade pectin (pectin is divided into three categories: protopectin, pectin and pectic acid, protopectin is insoluble in water). Under the action of protopectinase, the pectin can be converted into soluble pectin, so that the pectin is in a free state, and then other impurities on the surface will fall off. If the ordinary pectinase is used for scouring, its effect is not as good as that of the traditional process; if it is subsequently treated with hot water, the effect is even worse because the wax is not completely removed. In order to improve the removal effect of cotton wax, mixed non-ionic surfactant (its comprehensive HLB value is about 13, which is the HLB value for effectively removing dissolved wax) and natural D-Limonene (as an organic solvent dissolved in surface active agent) can be added. After scouring in the micelles of organic solvents), the waxiness will be significantly reduced, which can reach the level of traditional technology, but further research is needed to solve the problem of removing impurities from organic solvents.

Due to the formation of complexes between pectin and Fe3+, Ca2+, Mg2+ and other metal ions, the hydroxyl groups in the pectin molecules form ionic bonds with the components of the primary cell wall, and the pectin molecules are physically entangled with other components. Pectin exists in the form of protopectin, which is insoluble in water. Although enzymatic scouring can remove metal ions on the primary cell wall, the remaining metal ions will affect the removal of protopectin, and thus the removal of cotton wax. Therefore, adding a chelating dispersant during scouring can complex metal ions such as Ca2+, Fe2, Mg2+ and accelerate the dissociation of pectin when the enzyme cuts the primary cell wall. Another example is adding cellulase to the pectinase, the cellulase can attack the inner layer of the primary cell wall and the outer layer of the secondary cell wall, and can also accelerate the detachment of pectin and improve the refining effect. Pectinase only acts on pectin and does not cause fiber damage, but pectinase cannot remove cottonseed hulls.

Mechanism of action of protease: The protein content of cotton fiber is relatively high. At present, proteolytic enzymes have been used as scouring agents, but the effect is not good. The mechanism of action is to select the external proteolytic enzyme and the internal proteolytic enzyme according to the different positions, but the pretreatment conditions must be changed and the process conditions can be optimized to improve the treatment effect. Cotton fabrics are generally not used at present, and proteolytic enzymes are mainly used in wool fabrics.