Research On Optimization Of Pretreatment And Enzymatic Hydrolysis Process Of Poplar Fibers

The structure of natural wood fiber is tight and the chemical bond among cellulose,hemicellulose and lignin combination is large,so the accessibility between enzyme and fiber is low without the pretreatment of wood fibers.The efficiency of enzymatic hydrolysis of wood fiber can be improved with effective pretreatment of wood fibers.At the same time,the activity cellulose enzyme with protein mainly,which is the residues of microorganism metabolites,is influenced by many factors,such as temperature,pH and the kind of cellulose.In order to improve the yield of bioethanol and the efficiency of cellulose hydrolysis,the hydrolysis technology of wood fibers was optimized.In this paper,the conditions and parameters of pretreatment and enzyme hydrolysis were studied respectively and the optimization of technology was preformed using cypress wood fiber as raw material with the purpose of energy saving,greens environmental protection and high efficiency.The conclusions of the paper are as follows:The conditions and parameters of pretreatment of dilute phosphoric acid soaking of cypress wood combined steam blasting were optimized taking the concentration of reducing sugar in the enzymolysis liquid as evaluation standard with the help of single factor and orthogonal experiment.The structure of cypress wood and residues,which were obtained by blasting with and without phosphoric acid and blasting digestion sludge phosphoric acid,were characterized by XRD(X-Ray Diffraction),FTIR(Fourier Transform Infrared Spectroscopy),SEM(scanning electron microscope).The results shows that the degradation of hemicellulose is higher than that of cellulose while lignin has no change;through the orthogonal experiment,the accessibility of cellulose enzyme and fiber of each factor influence on the size of acid concentration>blasting pressure>time>ratio of cypress to phosphate;The optimal conditions of dilute phosphoric acid soaking of cypress combined steam blasting are as follows:the average of reducing sugar concentration in enzymolysis liquid is 27.02 mg/ml when pretreatment of cypress wood was conducted under the pressure of 2.5 MPa for 210 seconds with the 1%concentration of phosphoric acid and the ratio of 1:2 of material to liquid;pretreatment of phosphoric acid soaking combined steam blasting of cypress wood has improved accessibility of cellulose enzyme and fiber,so as to improve the efficiency of enzymatic hydrolysis due to destruction of the structure of cypress wood.The conditions and parameters of pretreatment of weak aqua ammonia soaking of cypress wood combined steam blasting were optimized taking the sugar concentration in the enzymolysis liquid as evaluation standard with the help of orthogonal experiment and response surface.The structure of cypress wood and residues,which were obtained by blasting with and without weak aqua ammonia and blasting digestion sludge phosphoric acid,were characterized by XRD,FTIR,SEM.The results shows that the degradation of hemicellulose is higher than that of cellulose whose content on the contrary is increased,which indicates that lignin can be induced effectively in in alkaline conditions;each pretreatment factors of blasting pressure,time,concentration of weak aqua ammonia plays an important role on the pretreatment of cypress wood and through the orthogonal experiment,the concentration of reducing sugar in enzyme liquid of each factor of pretreatment influence on the size of acid concentration>blasting pressure>time>concentration of weak aqua ammonia;the average of reducing sugar concentration in enzymolysis liquid is 19.683 mg/mL when pretreatment of cypress wood was conducted under the pressure of 2.52 MPa for 192 seconds with the 2.06%concentration of weak aqua ammonia and the assessed value of 19.229 mg/mL is obtained by simulation linear regression equation of response surface;pretreatment of weak aqua ammonia soaking combined steam blasting of cypress wood has improved accessibility of cellulose enzyme and fiber,so as to improve the efficiency of enzymatic hydrolysis due to destruction of the structure of cypress wood;The conditions and parameters of enzymolysis of cypress wood,such as temperature of enzymolysis,content of enzyme liquid,solid-liquid ration,pH value,were optimized using residues obtained by pretreatment of cypress wood under the optimal pretreatment conditions and the orthogonal experiment was preformed.The results shows that through the orthogonal experiment,the concentration of reducing sugar in enzyme liquid of each factor of enzymolysis influence on the size of acid concentration>blasting pressure>time>concentration of weak aqua ammonia and the enzymolysis has better efficiency when the enzymolysis is preformed with temperature of 50?,enzyme liquid content of 30 IU/g,solid-liquid of 1:11,pH value of 4.8.