Optimization Of Rubber Extraction Process From Eucommia Ulmoides Leaves

Eucommia ulmoides Oliver.is a unique ancient and widely distributed medicinal and gum tree species in China,Eucommia ulmoides gum is a natural polymer material in Eucommia ulmoides.It has attracted wide attention because of its unique properties different from clover rubber.In recent years,Eucommia gum has been a research hotspot in the field of material engineering.Efficient extraction is the basis of the development and utilization of Eucommia ulmoides gum.There are a variety of extraction methods of Eucommia ulmoides gum,but most of them are time-consuming,not environmentally friendly and easy to destroy the structure of Eucommia ulmoides gum,which changes the properties of Eucommia ulmoides gum,which also limits the application of Eucommia gum.The use of biological enzymes to destroy the cell wall and then extract Eucommia ulmoides gum is an environmentally friendly and effective extraction method.In this study,the gum of Eucommia ulmoides was extracted from Eucommia ulmoides leaves by mechanical grinding and response surface optimization.The main results are as follows.1)Mechanical grinding pretreatment of Eucommia ulmoides leavesUsing ball mill to pretreat Eucommia ulmoides leaves can expose Eucommia ulmoides gum without destroying Eucommia ulmoides gum.Through the use of different mesh screen to screen the ground Eucommia ulmoides leaves,it is concluded that the extraction effect is the best when the mesh number is 20 mesh.The rubber filament,powder and mechanically ground Eucommia ulmoides leaves were extracted respectively,and it was found that the use of Eucommia ulmoides leaf micelles to extract Eucommia ulmoides gum consumed the least solvent,which was 21m L,which was significantly different from that of Eucommia ulmoides leaves powder and ground Eucommia ulmoides leaves.The rubber content of Eucommia ulmoides rubber silk is the highest,and the rubber content of powder is the least,there is significant difference.The powder of Eucommia ulmoides leaves contains less gum and the impurities in the powder will enter the solvent,which will affect the purity of Eucommia ulmoides gum.In the experiment,the efficiency of gum extraction can be improved by about 30%by using the screened rubber filament.2)Analysis of enzymolysis reaction conditionsTaking the total sugar content and crude gum content of the enzyme hydrolysate as the response index,the effects of enzymatic hydrolysis temperature（40,45,50,55,55,60℃）,enzymatic hydrolysis time（3,5,5,7,9,11 h）,p H value（4.0,4.5,5.0,5.5,6.0）and enzyme dosage（0.5,0.75,1.0,1.5 g）on the effect of enzymatic hydrolysis were investigated.The enzyme has the highest catalytic activity and the best effect of enzymatic hydrolysis.When the enzyme dosage reached 1.25g,the gum content and total sugar content did not increase continuously;when the enzymatic hydrolysis time reached 7h,the enzymatic hydrolysis reaction was almost complete,and then the enzymatic hydrolysis efficiency would not be improved;when the enzymatic hydrolysis temperature reached 50,the gum content and total sugar content began to decrease with the increase of temperature,so the highest extraction rate of gutta-percha could be obtained when the enzymatic hydrolysis temperature was 50℃.3)Response surface optimization of enzymatic hydrolysis conditionsOn the basis of single factor test,the response surface test was carried out with p H value（A）,enzyme dosage（B）,enzyme hydrolysis time（C）and enzyme hydrolysis temperature（D）as independent variables,and the crude gum content extracted after enzyme hydrolysis as response value.The Adj R2 in the test is 0.9093,indicating that the reliability of the test data is high.According to the comparison of F value,the effects of various factors on the extraction of Eucommia ulmoides gum by enzymatic hydrolysis were as follows:d（enzymatic hydrolysis temperature）>B（enzyme dosage）>C（enzymatic hydrolysis time）>A（enzymatic hydrolysis p H）.Combined with the actual maneuverability,the best enzymatic hydrolysis conditions were determined as follows:p H4.9,enzyme dosage 1.5g,enzyme hydrolysis time 6.67h,enzyme hydrolysis temperature 45.7℃.the average rubber content of Eucommia ulmoides leaves was12.075%after Soxhlet extraction,Eucommia ulmoides leaves have a gum content of4.22%.4)Effect of Pretreatment on Extraction of Eucommia GumThere were significant differences among enzymatic hydrolysis group,ultrasonic treatment group and alkali cooking group.After pretreatment,the maximum reduction of micelles in Eucommia ulmoides leaves in each group was 23.42%in ultrasound group,63.43%in alkali cooking group and 38.76%in enzyme hydrolysis group,respectively.There were also significant differences in gum content between each treatment group and the control group treated only by grinding.the average increase of glue content in each group was 177.64%in ultrasonic group,142.66%in alkaline cooking group and 204.83%in enzymatic hydrolysis group.5)Analysis of Characteristic Parameters of Eucommia GumThrough XRD detection,the rubber yarn of Eucommia ulmoides leaves after enzymatic hydrolysis obviously appeared the characteristic peak of Eucommia gum at the diffraction angle of 2θ=18.80°,which may be due to the exposure of Eucommia gum after enzymatic hydrolysis.The gutta-percha extracted by enzymatic hydrolysis was identified by infrared spectroscopy.The stretching vibration peaks of methyl,methylene and carbon-carbon double bonds were observed at 2962.26cm^-1,2849.21cm^-1and 1664.76cm^-1,respectively.The molecular weight of Eucommia ulmoides gum was detected by gel permeation chromatography（GPC）.It was found that the molecular weight of Eucommia gum extracted from different pretreatment groups had four obvious peaks.At the peak of high molecular weight distribution,the average molecular weight of gutta percha gum in enzymatic hydrolysis group was higher than that in alkali cooking group and ultrasonic group.The average molecular weights of enzymatic hydrolysis group,alkali cooking group and ultrasonic treatment group were 47.31×10⁴,41.39×10⁴ and16.69×10⁴,respectively.There were significant differences in the average molecular weight of Eucommia ulmoides gum among the three pretreatment groups.among them,the average molecular weight of enzymatic hydrolysis group was the highest,which was nearly 3 times higher than that of alkali cooking group,followed by alkali cooking group,and the average molecular weight of ultrasonic treatment group was the lowest.The thermal stability analysis of Eucommia ulmoides gum showed that the mass loss mainly occurred in the range of 300℃to 450℃,but there was no significant difference in the TG curve of Eucommia ulmoides gum among different groups.