Research On Enzymatic Hydrolysis Of Corn Cob For Xylose Production

The purpose of this study is to make better use of corncob,the by-product of agriculture production in our country,and explore a low costing and maneuverable enzyme technology under moderate temperature without pollution to make oligomeric xylan of corncob thoroughly enzyme to xylose.1?There are two methods to pretreat corncob powder:one is high-temperature processing in water(1:5)as high as 120?,the other is the ultra-fine pulverization.This study focuses on the latter one.The following is single factor analysis on ultra-fine pulverization.(1)the effect of milling time on the yield of reducing sugar.The results,to a certain extent,indicated that the amount of reducing sugar increased gradually increased with the increase of milling time(from 0.5h/1200.76mg to 3 h/1530.78mg).With the increase of milling time,the grinding degree of corn cob also change,the the damage degree of previous cross-linked network structure of cellulose,hemicellulose,and lignin is more and more high.Therefore,it leads to better contact between enzyme and substrate.Considering the amount of reducing sugar increases little 1.5 hours later,therefore,the milling time is:0.5h,1h,2h in orthogonal optimization process due to energy dissipation.(2)the particle size of raw material is another factor influencing the effect of ball milling.If the particle size is too large,it will increase energy consumption,however,if the particle size is too small,the contact is not sufficient.Therefore,the initial particle size is the object of this study.The results show that,to a certain extent,the content of reducing sugar is inversely proportional to the particle size of raw materials,namely,the amount of reducing sugar increased with the decrease of particle size(experimental results:1310.25mg,1360.78mg,1350.56mg,1205.28mg,985.25mg).This may be attributed to the super-micro mill principle:the medium is crushed by friction and shear stress from grinding ball,so the medium itself can affect the experimental results.The results show that,reducing sugar content is the highest(1360.78mg)when particle size is 0.2mm,when the particle size is less than 0.2mm,the reducing sugar content reduces gradually.Therefore,the level of initial particle size are 0.45mm,0.2mm and 0.12mm in orthogonal experiment.(3)ratio of grinding media to material is also the object of this study,for it will influence the effect of ball milling.Research indicates that,ball material ratio,to some extent,is proportional to the amount of reducing sugar.nevertheless,the amount of reducing sugar decreased seriously when the ball to powder ratio was 20:1.This can be explained by that the main friction occurs among the balls when the ball to powder ratio increases,and it lead to less friction between ball and material,which is not conducive to smash.Comprehensive consideration,the ball to powder ratio contains there levels:4:1,8:1,16:1 according to orthogonal optimization.Considering the grinding effect and economy,the optimum conditions,based on ultra-fine pulverization of orthogonal optimization,were C1A1B1,the particle size is 0.45mm,ball material ratio 16:1,ball milling time is 2h.Under this condition,the amount of reducing sugar was 1879.14mg.2?As for the enzyme selection,results showed that,the effect of cellulase and xylanase enzyme performed better than a single enzyme either in high temperature group or ultra-fine powder group;for the superfine comminution group,the reducing sugar yield of combined enzyme of cellulose and xylanase were 1.24 times higher than that of xylanase,and 4.41 times than cellulase;as for combined enzymolysis from two enzymes on pretreated corncob as high as 120? yield increased from 0.6%to 17.2%;the results show that in the study of enzyme solution of combination interaction from two kinds of enzyme on ultrafine grinding corn core,xylose yield increased from 4.5%to 27.6%.3?A conclusion can be drawn from the optimization of enzymolysis experiment:the optimum technological conditions:the amount of enzyme substrate is 50IU/g,two combined enzymes,temperature is 40?,hydrolysis time is 6h.Under the optimum conditions,the enzyme can completely decompose substrate,which not only decreases the enzyme consumption,but also reduce the amount of corn cob,in accordance with the production goal "economic and efficient".At the same time,enzymatic 6h treatment is carried on 40 ?,a moderate temperature,thus it reduces the consumption of energy in the constant temperature,in this regard,it is more possible to turn the experimental analysis into actual production in the future...