Cellulase Enzymatic Treatment On Cellulosic Fiber

Although cellulase enzyme has been applied to the textile wet processing for many years, some application-related questions have not been clarified yet up to today. In this paper questions concerning cellulase activities measuring methods, relationship between cellulase activities and treatment effects, change of microstructure of cellulosic fibers and the inhibitive mechanism of dyestuff, etc, are studied to better understanding and utilizing cellulase treatment in textile processing.Filter paper, CMC and dewaxed cotton were used as substrate to measure the full activity, EGs activity and CBHs activity of enzyme, respectively. Cotton fabric samples were then treated with those activity-known enzymes to determine the relationship between enzyme activities and their treatment effects. It was shown that in the same weight loss level, endo-rich cellulases tend to produce in less tensile loss and fabric surface thickness effect, indicating EGs may exert "biopolishing" effect; while exdo-rich cellulases trend to impart fabric more tensile loss, less bending rigidity and higher compress rate, implying softness handle mostly come from CBHs' contribution.The total activity towards whole cellulase was studied with filter paper breaking time and the corresponding activity calculation formula was then defined. It was shown that the FPBT activity was most closely consistent with the weight loss. FPBT method could determine those which could not been determined by FPA. Also, it could be used to study the effect of cellobiose on cellulase activities and the inhibition of dyestuff in the enzymatic treatment bath against cellulase activities.Based on the analysis of the relationship between weight loss and enzymatic treatment time, cellulase concentration, respectively, a hypothesis was put forth as folio wings: in the course of long time enzymatic treatment, EGs play the major parts in the initial stage, delivering the major contribution to the hydrolysis, while CBHs contribute more and more with the time extending, will gradually and eventually dominates the hydrolysis contribution. As far as cellulase concentration is concerned, under the low concentration condition, EGs plays more remarkable roles in the hydrolysis, while with the concentration increase, CBHs will gradually show itscontribution and eventually overshadow the previous predominance of EGs. Many experimental phenomena can be explained by this hypothesis.X ray diffraction and SEM were used to determine and observe respectively the microstrure of cotton fiber before and after enzymatic treatment. It was shown that crystallinity and crystallite size had changed to different degree depending on the degree of weight loss, supporting the hypothesis that EGs and CBHs contribute differently in the course of long time hydrolysis. The dyeability of cotton fiber after enzymatic treatment was studied. Freundlich absorption type, dyeing affinity and dyeing entropy remained unchanged after enzymatic treatment, while dyeing uptake rate showed a slightly increase. Fiber absorption volume altered according to the change of weight loss, consistent with the changing rule of crystallinity and crystallite size, all supporting the raised hypothesis.The effect of dyestuff of dyed fabric on the hydrolysis of cellulase enzyme was studied. Four mechanisms based on other's study results were summed up as "complex mechanism", "covalent bond mechanism", "electrostatic mechanism" and "cover mechanism". Selected dyesruffs based on different structures and types were used to compare their inhibitive effects both on the fabric and in the solution. Spectrogram and FPBT method were used to determine the change of dyestuff solution after addition of cellulase solution and cellulase activity after the addition of dyestuff in the cellulase solution, respectively. It was found that complex, covalent bond and electrostatic mechanisms were not the major cause of dyestuff inhibition on cellulase hydrolysis. The higher the dyestuff affinity, the lower the weight loss of the dyed fab...