Research On Flax Degumming With Enzymes Cocktail

As one of the first natural fibers cultivated and used by human beings,flax fiber is known as the "Queen of the Plant Fiber",due to its excellent performance,such as fast heat dissipation,high strength,anti-pest and mildew,breathes well,etc.Compared with cotton fiber,which is the most commonly used fiber in textile industry,flax fiber contains not only large amount of cellulose,but also certain amounts of gummy materials including lignin,hemicellulose and pectin,etc.These gummy materials get adverse effects on the dyeing and finishing of the final/intermediate product.In order to obtained flax fiber with high textile value,degumming is necessary before the downstream application of the flax fiber.The traditional chemical degumming method always caused heavy environment pollution and cellulose degradation.Thus,developing a green and sustainability degumming method for flax fiber is of great urgent.And this study aims to provide a eco-friendly degumming method for flax fiber.The main research contents and conclusions are as follow:Firstly,as the laccase mediator system(LMS)has excellent delignification ability,the laccase TEMPO system(LT)was established by using TEMPO as a small molecular mediator.Taking delignification rate and fiber weight loss rate as the indicators,the effects of key factors including treatment temperature,p H value,bath ratio,time,laccase concentration,TEMPO concentration on the experimental results were discussed with single factor experiment.Under the optimal process conditions(laccase 1.5 U /m L,TEMPO 0.2 g /L,p H value 4.0,55 ℃,4 h,bath ratio 1:20),the lignin removal rate reached 35.61% and fiber weight loss rate 3.69%.Secondly,this study selected appropriate auxiliary process to strengthen the effect of LT system.Experimental results showed that the degumming effect of the system was further enhanced by the addition of 20 mmol /L EDTA(ELT).The lignin removal rate and fiber weight loss rate reached 56.74% and 5.12%;the residual gum content reached 22.32%,which was increased by 24.92% compared with the untreated samples.Moreover,the gummy materials on the surface of fiber were reduced,and the fiber fineness was significantly improved after the ELT treatment.In addition,ELT system got little damage to cellulose and maximizes the retention of fiber strength,compared with the traditional chlorine bleaching process.The tenacity and fineness flax fiber treated with ELT increased by 45.70% and 41.6%,respectively.However,the whiteness has no obvious change after degumming,which means the originally color flax fiber style has been retained at the same time.Then,to improve the removal rate of pectin and hemicellulose,enzyme cocktail system consisting of pectinase and hemicellulose was used for flax degumming.The Placket-burman and Box-Behnken response surface method was used to select the key factors influencing the effect of degumming and the optimal reaction condition.Result showed that hemicellulase concentration,pectinase concentration,reaction time and temperature significantly influenced the effect of degumming.Then,this study explored the appropriate response interval of these four factors with the climbing experiment.Subsequently,the mathematical model was established with the residual rate(Y1)and the weight loss rate(Y2)as the dependent variable.The optimal solution recommended by the model was: 3 h,51 ℃,5.1 g/L pectinase and 1.1 g/L hemicellulase.Confirmation experiments showed that the residual gum rate and weight loss rate of flax fiber is 17.02% and 7.23% with the deviations from the predicted values of 1.43% and 4.37% respectively;which proved the that the effectiveness of the mode.The delignification rate of flax fiber under the optimal condition was 8.27%,which was much lower than that of LT and ELT.Finally,this study combined ELT system with the enzyme cocktail system by different mode(A: ELT-Enzyme cocktail;B: Enzyme cocktail-ELT;C: one bath of ELT and Enzyme cocktail,p H 5.5;D one bath of ELT and Enzyme cocktail,p H 4.0)to further improve the effect of degumming.Results showed that fractional method(A)got better degumming effect than that of the synchronous method(C and D)and single ELT or single enzyme cocktai.Thus,the optimal degumming process was selected as: enzyme cocktail treatment-deionized water washing-ELT system treatment-5 min boiling-deionized water washing-drying.Under the optimal treatment condition,the fiber got good dispersion,high splitting degree,smooth fiber surface and the fiber weight loss rate can reach 11.2%,the residual gum rate is16.21%,and the fiber lignin removal rate after treatment can reach 79.69%.In addition,it could be deduced that the removal of single component(hemicellulose or lignin or pectin)could promote the removal of the other kinds of gummy materials;and the promoting effect of hemicellulose and pectin removal on lignin degradation was stronger than promoting effect of lignin removal on hemicellulose and pectin degradation.