Enzymatic Treatment Of Pulp Fibers With High-Content Of α-Cellulose

The application of enzyme in the pulp industry has been paid great attention all over the world. The dissertation studied the removal of lignin, hemicellulose and fines from pulp and the change of pulp fibers in the process of dealing with pulp by cellulase and xylanase, primarily involving the biosynthesis and the fractionation of cellulase and xylanase in order to dealing with pulp of high content of a -cellulose, the effects of removing lignin, hemicellulose and fines from pulp and the change of pulp fibers of high degree of polymerization such as a -cellulose with the change of dosage of cellulase and xylanase, time, pH, temperature and pulp concentrations. The experimental results are as following:1. Using crude xylan as the substrate could induce xylanase with less damage to pulp fibers of high degree of polymerization such as a -cellulose. Using Mandels nutrients and sulfite pulp as the substrate could induce cellulase with high xylanase activity.2. Dealing with pulp by cellulase, xylanase and mixed enzymes could remove lignin, hemicellulose and fines from it.3. Dealing with pulp by cellulase, pulp fibers were destroyed seriously and the recovery ratio of a -cellulose was less than 95% at different cellulase dosage, time, pH, temperature and pulp concentrations. Increasing cellulase dosage or extending time, the damage of pulp fibers was worse. The change of pH, temperature and pulp concentrations made no obvious impact on enzymatic hydrolysis of pulp.4. Dealing with pulp by xylanase and controling the time less than 6 hours, pulp fibers were destroyed lightly and the recovery ratio of a -cellulose was more than 95% at varied xylanase dosage, time, pH, temperature and pulp concentrations. The influence of the enzymatic hydrolysis to pulp by the change of xylanase dosage and time was more serious than that by the change of pH, temperature and pulp concentrations. Dealing with pulp by fractionated xylanase, pulp fibers were destroyed lightly and the recovery ratio of a -cellulose was more than 95%. The damage of pulp fibers by A, B, C fractions of xylanase was more serious than that by crude xylanase. The damage ofpulp fibers by D fraction of xylanase was lighter than that by crude xylanase.5. Dealing with pulp by the mixed enzymes, the damage of pulp fibers was more serious than that by xylanase solely. The damage of pulp fibers was more and more serious with increasing the proportion of cellulase in the mixed enzymes. The damage of pulp fibers was lighter by the enzyme mixture of crude xylanase and D fraction of cellulase. The damage of pulp fibers was more serious by the enzyme mixture of crude xylanase and A fraction of cellulase. The damage of pulp fibers by the enzyme mixture of crude xylanase and B or C fractions of cellulase was as same degree as that by the enzyme mixture of crude xylanase and crude cellulase.Dealing with pulp by xylanase, lignin, hemicellulose and fines could be removed from it, and the damage of a -cellulose is very light simultaneously. Dealing with pulp by cellulase could remove more lignin, hemicellulose and fines from it than by xylanase. And the damage of a -cellulose was more serious by cellulase than by xylanase. The experimental results of this dissertation was a reference of choosing enzyme for practice application, improving the drainage velocity of pulp and the ventilation of pulp, extending the application of pulp and increasing the quality of paper.