Abstract:
This chapter focuses on the different sources of natural rubber, history of Hevea sp. rubber, composition, chemistry and properties of Hevea latex, the botany, origin and ecology of the rubber tree, rubber biosynthesis, rubber tree cultivation (propagation, crop management, rubber tapping and pests and diseases), research needs, conventional and molecular breeding methods, rubber processing (latex concentrate, dry rubber and quality control) and manufacturing of rubber goods. The natural rubber trading, rubber products, additional uses of the rubber tree, fate of used rubber products and the current status and future prospects of the rubber industry are also discussed.Keywords:
Hevea
ABSTRACT The superior properties of natural rubber (cis-1,4-polyisoprene [NR]) are a function of its structure and composition, properties that still remain a mystery and that are irreplaceable by any synthetic rubber. NR from guayule (Parthenium argentatum) has been gaining special interest for its hypoallergenic properties while maintaining superior mechanical properties that are commonly associated with the Brazilian rubber tree (Hevea brasiliensis), the most common source of NR. Techniques exist to isolate washed rubber particles (WRPs) that contain enzymatically active rubber transferase, to study NR biosynthesis, and previous work on the in vitro NR growth in Hevea has demonstrated the presence of around 50 wt% of a low molecular weight ([MW], Mn <10 000 g/mol) fraction. Structural and compositional analyses of this low MW fraction in Hevea are challenging due to the high protein content. We discuss the analysis and composition of guayule latex and WRPs using high-resolution Size Exclusion Chromatography. We also discuss the composition of the soluble fraction of inactive guayule latex using matrix-assisted laser desorption ionization/time of flight mass spectrometry.
Hevea
Fraction (chemistry)
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Abstract Introduction Occurrence of Polyisoprene Chemical Properties of Rubber The Latex Vessel System Composition of Latex Molecular Weight of Rubber Historical Outline Rubber Precursors Rubber Formation on Rubber Particles Stereochemistry of Rubber Biosynthesis Initiator of Rubber Synthesis Biosynthesis Pathway in Hevea brasiliensis Formation of IPP Initiation of Rubber Molecules Chain‐Elongation of Rubber 13 C‐NMR Study of Rubber Molecules Enzymes in Hevea brasiliensis Enzymes for the Formation of Mevalonic Acid Enzymes for the Formation of IPP Rubber Transferase Genetic Basis Rubber Biosynthesis‐Related Proteins Defense‐Related Proteins Latex Allergens Other Enzymes in Hevea Rubber Biosynthesis Pathways and Genes in Guayule and other Organisms Guayule Rubber Biosynthesis Rubber Synthesis in Indian Rubber Tree Rubber Synthesis in Fungi Production in Transgenic Plants and Recombinant Microorganisms Outlook and Perspectives Relevant Patents Stimulation of Rubber Yield and Rubber‐Producing Plants Rubber Biosynthetic Genes and their Transformation Synthetic Use of Enzymes from H. brasiliensis Enzymes from Hevea and their DNA Sequences Acknowledgements
Hevea
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Hevea
Particle (ecology)
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Citations (56)
Abstract Natural rubbers are synthesized in thousands of species covering most plant families; moreover, rubber has been obtained commercially from over a dozen of them. A later report has suggested that polyisoprene formation is limited to dicotyledonous angiosperms. In recent years there has been renewed interest in developing alternative sources of natural rubber, different from Hevea brasiliensis. In particular there has been considerable development of guayule as a source of natural rubber. As a result there is a considerable body of recent results, using new techniques and extending older work concluded in the 1950's, which give new insight into the production of rubber in plants. This paper will mainly deal with guayule because it can ideally serve as a background for understanding the production of rubbers in other plants, including hevea. First, it is necessary to describe the physical nature of the rubber from guayule and where in the plant it is formed. Figure 1 shows a cross-section of a stem of guayule. The individual cells (parenchyma cells) are the site of rubber manufacture. The rubber can finally be seen as the small latex droplets inside a single cell (Figure 2). Thus the study of the natural rubber in guayule involves the isolation of the latex particles from the cell. It is extremely easy to separate an industrial rubber from other parts of the plant, including resin, by either laboratory or pilot plant methods. However, it is more difficult to get fresh latex in which no additional particle coagulation has occurred. The description of the average latex particle size and the distribution of sizes has been made and is needed to discuss the biosynthesis of rubber. It will not be discussed further. The question addressed in this paper is the chemical structure of the rubber in the plants—the micro-structure of the rubber, the molecular weight distribution, and the branching or gel content. Guayule natural rubber has the remarkable feature of containing no gel when taken directly from a fresh plant and carefully handled in the laboratory. Even the material from the pilot plant extraction process contains only 1–3 per cent gel. This paper describes extensively the chemical structure of natural rubber extracted from fresh guayule plants. Less extensive measurements on chicle, gutta-percha, and castilla elastica are also reported. Finally, all of the data are analyzed to determine if a model of rubber production can be formulated to encompass all of the above plants. Earlier, a model was proposed for guayule only. In this model the polyisoprene chain is polymerized on the polymerase enzyme site by recurring attachment and intermittent polymerization until the rubber droplet (containing a single polymer chain) can no longer be stabilized or further polymerized by the enzyme.
Hevea
Synthetic rubber
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Hevea
Strain (injury)
Degradation
Synthetic rubber
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Isopentenyl pyrophosphate
Hevea
Isoprene
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Natural rubber is one of the most important polymers produced by plants because it is a strategic raw material used in more than 40,000 products. It has unique properties as a polymer owing to its specific structure, its high molecular weight and yet-to-be-defined contributions of minor components in the latex. Among over 2500 rubber-producing plant species, the Para rubber tree (Hevea brasiliensis Muell. Arg.) is presently the only commercial source of natural rubber. The objective of this review is to provide readers with information on the newest trends and market conditions of natural rubber and also explain the historical background and a global view of Hevea breeding and genetics, together with information about alternative resources.
Hevea
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Rubber trees are among the important cultivated crops in Malaysia, and have contributed to the country’s overall economic growth since the 1950s. However, the existing anatomical and morphological studies are relatively insufficient. Currently, Hevea brasiliensis has been cultivated and planted commonly as a commercial planting clone, while Hevea camargoana remains to be a non-cultivated and underutilized rubber species. For many years, there only exists little information both in private plantations and government agencies that have carried out anatomical and morphological assessments on these underutilized species. There is little information about the characteristics of H.camargoana, thus raising the issue among plant breeders on how to best use this underutilized rubber species. This study attempts to investigate the taxonomic values and characteristics of Hevea brasiliensis and Hevea camargoana through anatomical and morphological studies.
Hevea
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Rubber particles are important organelles in latex for rubber biosynthesis in rubber tree (Hevea brasilensis). The crucial enzymes in rubber biosynthesis such as rubber transferase, rubber elongation factor and other proteins and so on were all located at the surface or embedded in the membranes of rubber particles. In this study, the membrane proteins of rubber particles had been successfully isolated, and further examined by SDS- PAGE (10 % w/v gel). Afterwards, 2-DE was performed using the nonlinear gel strip pH3-10 to separate the membrane proteins. About 520 protein spots were obtained on the silver stained gel. Some protein spots were taken randomly and analyzed by MALDI-TOF. Through searching the protein database and blast, some previously known proteins were further identified including the rubber elongation factor (REF), rubber allergic protein Hev 3, etc, and some were unknown proteins. From the silver stained gel, it could be seen that the REF contributed substantially to the membrane proteins of rubber particles, indicating that REF might have a very important function in the rubber biosynthesis. JA and ET responsive proteins were also found in the membrane proteins, which implied that JA and ET might regulate rubber biosynthesis through these responsive proteins on the membranes of rubber particles in the rubber tree. The establishment of the 2-DE system on the rubber particles is conducive to investigating the components and changes of rubber particles membrane proteins.
Hevea
Elongation factor
Elongation
Organelle
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