| Natural rubber is widely used due to its excellent performance and irreplaceability.The domestic natural rubber production can only meet 20%of China’s natural rubber demand,and the dependence on foreign imports exceeds 80%,which may bring dangers in the development of various fields in China.Therefore,it is urgent to find some other plant rubber resources.The most widely studied plant rubbers are Taraxacum koksaghyz(TKS),Guayule rubber and Eucommia ulmoides gum(EUG).The domestic and foreign research on TKS mostly focused on the upstream links of germplasm screening,cultivation technology,gene regulation,proteomics,etc.,the technology of extraction process of TKS latex has yet to be further studied.The preliminary research on the extraction process of TKS latex was carried out in this paper.The research is mainly divided into three parts.Firstly,the rubber distribution and the component content analysis of TKS roots;secondly,the study on the technology of extraction process of TKS latex,and finally the analysis of latex structure and properties.1.The transverse section of the root of TKS was observed under an optical microscope to observe the distribution of rubber at the root,at the same time the morphology of the laticifer cells was observed as well.The component content analysis of TKS roots founds that it has the highest moisture content in TKS root,followed by lignin and hemicellulose content,while the rubber content is currently only about 6%(dry weight ratio).2.The actual extraction efficiency replaces the apparent extraction efficiency,improving the accuracy of the evaluation of the latex extraction process,the main process of TKS latex extraction was determined as follows:root pretreatment,shaking/stirring in buffer environment,suction filtration,centrifugal separation,etc.,through the four steps of the basic extraction process to make the latex extraction efficiency can reach about 67%.The effect of polyphenol oxidase(PPO),which is known as "latex coagulation factor",in the latex extraction process was investigated.It was found that its activity was most inhibited by temperature.When the extraction temperature was 50℃,the latex extraction efficiency reached 80.51%.The influence of the amount of PPO activity inhibitors such as sodium sulfite(Na2SO3)and dithiothreitol(DTT)was weak,and the comparison between the two inhibitors proved that Na2SO3 promoted latex extraction better than DTT.Ameliorating the latex extraction device revealed that the extraction efficiency of latex using a shaker was generally higher than that when using a stirrer.After the above research,an optimal process route was finally determined:the TKS roots within 24 hours of storage time were selected for pretreatment;Na2SO3 was selected as the inhibitor of polyphenol oxidase,and its concentration was set 0.1%of the extraction buffer which was charged at a solid-liquid ratio of 1:2,then the system was shaken at 150 rpm for 30 min at a temperature of 50℃;the system was collected and filtered,the slurry was collected and centrifuged to collect the upper latex;Repeat the above extraction process twice can make the final extraction efficiency reach about 80%.3.The structure and properties of natural latex,the extracted TKS latex,and the latex directly collected from the plants were compared.The appearance analysis showed that both of them had the same appearance and were milky white;after centrifugation,they were divided into four parts from top to bottom:rubber particles,F-W particles,whey and solid yellow body;The results of component analysis showed that the water content in TKS latex was between 31.6%and 45.50%;the latex concentration ranged from 54.54%to 68.25%;the protein concentration was 13.51 mg/mL,which was slightly higher than the natural latex of 11.91 mg/mL;The ash content of both is low and its value is about 3%.The results of infrared spectroscopy,nuclear magnetic resonance spectroscopy and thermogravimetric analysis showed that the structure and composition of the three latexes were basically the same.The results of gel permeation chromatography showed that the molecular weights of the three latexes all showed a bimodal distribution,and the molecular weight of the latex collected from TKS was low;scanning electron microscopy observation and laser particle size analyzer analysis showed that the natural latex and TKS latex rubber particles were both core-shell structure and the size distribution was bimodal,which was consistent with the GPC analysis results.The latex concentration analysis showed that the TKS latex concentration was higher and the distribution was narrower.The protein concentration of TKS latex is higher than that of natural latex.In summary,the difference between TKS latex and natural latex is small,so the TKS latex obtained by the extraction process in this paper has certain practical value. |
