Alternative Source Of Natural Rubber Research Articles

Epigenetic variation in early and late flowering plants of the rubber-producing Russian dandelion Taraxacum koksaghyz provides insights into the regulation of flowering time

The Russian dandelion (Taraxacum koksaghyz) grows in temperate zones and produces large amounts of poly(cis-1,4-isoprene) in its roots, making it an attractive alternative source of natural rubber. Most T. koksaghyz plants require vernalization to trigger flower development, whereas early flowering varieties that have lost their vernalization dependence are more suitable for breeding and domestication. To provide insight into the regulation of flowering time in T. koksaghyz, we induced epigenetic variation by in vitro cultivation and applied epigenomic and transcriptomic analysis to the resulting early flowering plants and late flowering controls, allowing us to identify differences in methylation patterns and gene expression that correlated with flowering. This led to the identification of candidate genes homologous to vernalization and photoperiodism response genes in other plants, as well as epigenetic modifications that may contribute to the control of flower development. Some of the candidate genes were homologous to known floral regulators, including those that directly or indirectly regulate the major flowering control gene FT. Our atlas of genes can be used as a starting point to investigate mechanisms that control flowering time in T. koksaghyz in greater detail and to develop new breeding varieties that are more suited to domestication.

Replacement of Carbon Black with Coppiced Biochar in Guayule Rubber Composites Improves Tensile Properties

Natural rubber, sourced from Hevea brasiliensis trees mainly in southeast Asia, is a critically important resource for transportation, national security, and medical products, among other uses. The guayule shrub is a domestic alternative source of natural rubber that is emerging with advantages over Hevea since it is well-suited for many medical and consumer applications. Biochar is a sustainable form of carbon made from biomass that is a potential replacement for petroleum-sourced carbon black, the most common filler for rubber composites. The coppiced-wood species hybrid poplar (Populus × canadensis) and Paulownia elongata are both rapidly growing hardwoods that have shown promise as feedstocks for biochar that can be used as fillers in common rubber composites such as Hevea natural rubber, styrene-butadiene, and polybutadiene. In this work, poplar and paulownia biochars were used to partially replace carbon black as filler in guayule rubber composites. Guayule composites with up to 60% of the carbon black replaced with poplar or paulownia biochar had higher tensile strength, elongation, and toughness compared to the 100% carbon black-filled control. These composites would be excellent candidates for rubber applications such as gloves, belts, hoses, and seals, while reducing dependence on fossil fuels and Hevea natural rubber.

Preparation of Taraxacum kok-saghyz Rubber and Biofuel Ethanol Simultaneously by the Yeast Fermentation Process.

Taraxacum kok-saghyz(TKS) rubber is considered the most ideal alternative source of natural rubber (NR). Extracting rubber from TKS with high quality, low cost, and low pollution is the basis of commercial development. The TKS roots were subjected to morphological observation and detailed compositional analysis. Scanning electron microscopy (SEM) images confirm that rubber filaments are physically entangled with plant tissues due to differences in molecular polarity. Compared with the traditional solvent TKS rubber extraction process, a new rubber extraction process developed in this study, namely, the microbial extraction (″ME″) process, is less harmful to the environment and lower in cost. The ″ME″ process is divided into three steps: dilute acid pretreatment process, enzyme degradation process, and fermentation process. After each step is completed, the purity of TKS rubber will gradually increase from 84.8% to 93.8 to 95.5%. The TKS rubber finally obtained fully meets the requirements of the traditional rubber industry, especially the tire industry. Besides, the yield of biofuel ethanol, a by-product of cellulose fermentation, reaches 2.05 g/100 g of TKS roots (dry weight), which can effectively reduce the production cost of TKS rubber. In the rubber extraction process, microorganisms have little effect on the quality of TKS rubber. The results show that the molecular weight and chemical structure of TKS rubber is very close to NR, so the ″ME″ process can be used as a new method for large-scale extraction of TKS rubber.

Genome-Wide Identification and Spatial Expression Analysis of Histone Modification Gene Families in the Rubber Dandelion Taraxacum kok-saghyz.

Taraxacum kok-saghyz (Tks), also known as the Russian dandelion, is a recognized alternative source of natural rubber quite comparable, for quality and use, to the one obtained from the so-called rubber tree, Hevea brasiliensis. In addition to that, Tks roots produce several other compounds, including inulin, whose use in pharmaceutical and dietary products is quite extensive. Histone-modifying genes (HMGs) catalyze a series of post-translational modifications that affect chromatin organization and conformation, which, in turn, regulate many downstream processes, including gene expression. In this study, we present the first analysis of HMGs in Tks. Altogether, we identified 154 putative Tks homologs: 60 HMTs, 34 HDMs, 42 HATs, and 18 HDACs. Interestingly, whilst most of the classes showed similar numbers in other plant species, including M. truncatula and A. thaliana, HATs and HMT-PRMTs were indeed more abundant in Tks. Composition and structure analysis of Tks HMG proteins showed, for some classes, the presence of novel domains, suggesting a divergence from the canonical HMG model. The analysis of publicly available transcriptome datasets, combined with spatial expression of different developmental tissues, allowed us to identify several HMGs with a putative role in metabolite biosynthesis. Overall, our work describes HMG genomic organization and sets the premises for the functional characterization of epigenetic modifications in rubber-producing plants.

Alkaline pretreatment of Taraxacum kok-saghyz (TK) roots for the extraction of natural rubber (NR)

Natural rubber (NR) is an essential biomaterial the supply of which is insecure. Taraxacum kok-saghyz (TK), a rubber-producing dandelion, is an alternative source of NR that has excellent potential for commercial development. Scalable methods for rubber extraction at high yield, quality and purity are needed to meet this potential. We previously developed an aqueous, enzymatic method for the extraction and purification of NR from TK roots. Alkaline pretreatment significantly improved the yield of TK NR using this method, but its effects on NR yield, purity and quality at a range of base concentrations and temperatures was not tested. In this study, TK roots (after inulin extraction) were pretreated at sodium hydroxide loading rates of 0, 33, 66 and 132 mg NaOH/g and temperatures of 25, 70, 125 and 160 °C. Treatment with pectinase and cellulase enzymes was used to solubilize root structural carbohydrates and liberate NR. Rubber quality and impurities were then characterized. Results showed that increasing NaOH loading rate and temperature significantly improved rubber yield, but reduced rubber molecular weight and rubber gel content. Rubber purity and thermal properties were largely unaffected by pretreatment conditions. FTIR and SEM analysis revealed that alkaline pretreatment primarily altered protein and other secondary components of TK NR.

Comparative Transcriptome Analysis in Taraxacum koksaghyz to Identify Genes that Determine Root Volume and Root Length.

The Russian dandelion (Taraxacum koksaghyz, family Asteraceae) produces large amounts of natural rubber in the laticifers of its roots. This species has been proposed as an alternative source of natural rubber to augment or partly replace the rubber tree (Hevea brasiliensis) but domestication would require genetic improvement to increase rubber yields and agronomic optimization to facilitate harvesting and processing. Optimization has focused thus far on the size and shape of the roots, the primary storage organ for natural rubber and inulin. However, the corresponding genetic factors are poorly understood. Here we describe the comparative transcriptomic analysis of root tissues from T. koksaghyz plant sets featuring different root sizes and shapes, aiming to identify differentially expressed genes correlating with root length or root diameter in the upper root and root tip. The resulting datasets revealed multiple candidate genes for each trait and root part, including a glucan endo-1,3-β-d-glucosidase, an allene oxide synthase 3, and a TIFY10A/JAZ1 homolog. These three genes were tested by qRT-PCR in outdoor-grown plants with diverse root morphology, and the expression of two genes correlated with the appropriate root morphotype, confirming the effectiveness of our method. We evaluated the candidate genes to gain insight into their potential functions in root development. Such candidate genes could be suitable for marker-assisted breeding programs in the future.

Guayulin content in guayule (Parthenium argentatum Gray) along the growth cycle

The commercial development of guayulins might help spur industrial-scale applications of guayule as an alternative source of natural rubber, making necessary to build knowledge on their seasonal response and accumulation in plants. In the present study, the seasonal content of the four known guayulins (A–D) was profiled in 14 different guayule accessions, including hybrids, from age 13 months to age 23 months. Analysis revealed that the accessions could be categorized into four groups based on guayulin content and potentially reflective of their genetic origin and hybridization: one rich in guayulin A, one rich in guayulin C, one rich in guayulin D, and one with intermediate values. Despite the evident differences in guayulin profiles, all four groups shared the same general response. The content of guayulins A and B increased between April and September, followed by a drastic fall in content in November likely triggered by low temperatures, and then a gradual recovery. By contrast, the content of guayulins C and D was much more stable, especially for those accessions showing the highest production. The relationship between the guayulins was useful to characterize their evolution during the growth cycle, with some groups halting production of guayulins during the summer (group rich in guayulin C) and others initiating production earlier, after the winter period (groups rich in guayulin A and those with intermediate values). The higher producers of guayulins were the accessions 11591(CL-1) and AZ-6, and the best harvest time was between September and November, depending on climatic conditions.

Sustainable Natural Rubber

Para rubber tree, the current source of natural rubber is susceptible to disease and has a history of extinction. To make natural rubber a sustainable product, number of efforts are underway to obtain alternative sources of natural rubber. Guayule and Russian dandelion are currently the two strong candidates. Study on guayule, a bush that grows in an arid area has been on and off for many decades. The prohibitive cost of processing rubber always discouraged continuous effort. In 2014, an environmentally friendly pilot plant using solvent extraction technology was built at the outskirt of Mesa, Arizona, with a nearby 280-acre farm. The new facility will not only significantly improve productivity of rubber manufacturing, but also physical properties are equivalent to the current source, para rubber. Another alternative source of natural rubber, Russian dandelion, a weed that grows in a temperate climate was also discussed.

Temperature requirements for guayule seed germination

Guayule (Parthenium argentatum A. Gray) is an alternative source of natural rubber. Direct-seeding is critical to commercialization of guayule and quantifying variability in seed germination response to temperature is necessary. A thermogradient table was used to measure germination rates of the 44 most commonly available Parthenium accessions under 10 temperature gradients. The optimal temperature for seed germination ranged from 17.8–26.9 °C, with an average temperature of 21.8 °C. The sensitivity of seed germination to temperature range varied significantly among accessions. When compared with the highest germination rate at optimal temperature, relative germination rate at 10 °C and 35 °C represented low and high temperature tolerance for seed germination in guayule accessions, respectively. The two accessions with >70 % relative germination rate at 35 °C, R1109 and P. incanum (mariola), had the optimal temperature for germination above 26.6 °C. Six accessions with >70 % relative germination rate at 10 °C, 11591, R1110, PARL 935, CAL-3, 11605, and PARL 920, had a range of 17.8–21.7 °C optimal temperature for germination. This study indicates that guayule and other Parthenium accessions varied significantly in temperature requirements for seed germination. These temperatures can serve as a guide to seasonal timing for direct seeded field planting.

Antioxidant Sources from Leaves of Russian Dandelion.

Taraxacum kok-saghyz (TKS) is a dandelion species native to Kazakhstan, Uzbekistan and north-west China, considered as a promising alternative source of natural rubber from its roots. The aim of this study was to investigate the possible exploitation of TKS leaves, a rubber byproduct, as a source of phenolic compounds with antioxidant properties for potential applications in forage, nutraceutical and pharmacological fields. Two accessions (TKS016, TKS018) grown under Mediterranean conditions of Sardinia were evaluated at vegetative and flowering stages. The leaves of TKS018 had the highest antioxidant capacity (19.6 mmol trolox equivalent antioxidant capacity 100 g-1 ), total phenolic (106.4 g gallic acid equivalent kg-1 ), tannic phenolics (58.5 g gallic acid equivalent kg-1 ) and total flavonoid contents (22.9 g catechin equivalent kg-1 ). At both phenological stages, TKS016 showed significantly lower values than TKS018 in 1,1-diphenyl-2-picrylhydrazyl (DPPH), total phenolic and tannic phenolics. Six individual molecules were identified, namely chlorogenic, cryptochlorogenic, caffeic, sinapic, chicoric and 3,4-dimethoxycinnamic acids. Chicoric (8.53-10.68 g kg-1 DW) and chlorogenic acids (4.18-7.04 g kg-1 DW) were the most abundant. TKS leaves represent a valuable source of chicoric acid with potential application as antioxidant to be used as herbal medicine and nutrition for production of healthy food/feed.

Development of novel processes for the aqueous extraction of natural rubber from Taraxacum kok‐saghyz (TK)

AbstractBACKGROUNDTaraxacum kok‐saghyz (TK) is a rubber‐producing plant being developed as a commercial alternative source of natural rubber (NR). The objective of this study was to investigate processes to extract high quality NR at high yield and purity from TK. Rubber is formed in the roots of TK and exists in mostly solid form. Previously used mechanical processes extract NR from TK roots at low purity (< 90%) that does not meet industry standards (≥ 99.8%). To improve this, the effects of root chopping, enzymatic hydrolysis, pebble milling and alkaline pretreatment and purification on NR yield, purity and quality were investigated.RESULTSEnzymatic digestion (with and without alkaline pretreatment), yielded rubber at the highest yield (∼80%) and purity (99.4%). Alkaline pretreatment of roots improved NR yield and did not adversely affect quality. More rubber was extractable from chopped roots than whole roots, but the rubber was less pure. Alkaline purification of the extracted crude rubber further increased rubber purity but reduced rubber molecular weight.CONCLUSIONEnzymatic digestion with or without alkaline pretreatment forms the basis of aqueous processes that could be used for large‐scale, efficient extraction of TK rubber at high yield, purity and quality to meet industry standards for NR. © 2019 Society of Chemical Industry

Transcriptome analysis of rubber biosynthesis in guayule (Parthenium argentatum gray)

BackgroundNatural rubber is currently produced nearly exclusively from latex of the Para rubber tree, Hevea brasiliensis. The desire to reduce the environmental cost of rubber production, fears of pathogen susceptibility in clonal Hevea plantations, volatility in the price of natural rubber, and increasing labor costs have motivated efforts to diversify the supply of natural rubber by developing alternative rubber crops such as guayule (Parthenium argentatum Gray). In Hevea, latex is produced as an exudate following wounding while in guayule, rubber is deposited within the cortical parenchyma and its production is strongly influenced by environmental conditions.ResultsTo better understand the enzymology and regulation of guayule rubber biosynthesis and to identify genes with potential uses in the improvement of rubber yields, we conducted de novo transcriptome assembly and differential gene expression analyses of this process in guayule. This analysis supports a role for rubber in the defense against pathogens, identified new enzymes potentially involved in the biosynthesis of rubber as well as transcription factors specifically expressed in rubber-producing tissues.ConclusionsData presented here will be useful in the improvement of guayule as an alternative source of natural rubber and in better understanding the biosynthesis of this critical polymer. In particular, some of the candidate transcription factors are likely to control the rubber biosynthesis pathway and are good targets for molecular breeding or engineering of guayule plants with higher and more consistent production of rubber.

Rapid and complete removal of guayule (Parthenium argentatum) leaves by cryodefoliation, and freeze and thaw induction of rubber particle coagulation

Production of natural rubber (NR), a vital natural resource for modern economies, currently is completely dependent upon tropical cultivation of the Para rubber tree (Hevea brasiliensis, Müll. Arg). One promising source of alternative rubber is guayule (Parthenium argentatum, Gray), which is currently being developed as an alternative source of NR. Guayule rubber accumulates as rubber particles in bark parenchyma and can be extracted in the form of latex by homogenizing the bark and then separating the latex from the non-latex components by centrifugation. Latex separation and purification processes are significantly hindered by fine solids from the co-homogenized leaves. Therefore, complete removal of leaves before homogenization is highly desired. However, guayule leaves do not naturally abscise and chemical defoliants cannot be utilized since these dehydrate the shrub and coagulate the latex, and physical leaf removal processes are tedious or inefficient. We demonstrate that liquid nitrogen can be used to embrittle the leaves without freezing the bark parenchyma, completely removing the leaves with a single physical blow, and then the defoliated branches can be homogenized with no loss of latex-containing bark and no leaf contamination. Under longer freezing times, rubber coagulation occurred in partially frozen tissue and during slow thawing. Furthermore, we demonstrate that the rubber coagulation, which occurs when guayule branches are frozen through and thawed before homogenization, can be avoided by rapid homogenization of the flash frozen branches in ambient temperature aqueous extraction buffer.

Simultaneous quantification of rubber, inulin, and resins in Taraxacum kok-saghyz (TK) roots by sequential solvent extraction

Taraxacum kok-saghyz (TK) is being developed as an alternative source of natural rubber (NR). Three valuable constituents of TK roots are NR, inulin and resins. Previous methods required independent measurements to quantify each of these constituents. In addition, the co-extraction of non-target compounds leads to significant errors in the measurement of rubber concentration in roots and processed samples. Accelerated solvent extraction (ASE) is an automated method that allows the rapid extraction of samples with multiple solvents and excellent repeatability. The objective of this study was to develop an optimized multi-solvent ASE method to improve the accuracy of NR, inulin and resin quantification in TK roots. Water, acetone, and hexane were used to extract inulin and saccharides, resins, and rubber, respectively. Root preparation, extraction temperatures and times, sample size (1.0 and 0.25 g), and the number of extractions were evaluated. Two, 40-min water extractions at 95 °C; one, 40-min acetone extraction at 40 °C; and three, 20-min hexane extractions at 160 °C were determined to be optimal based on completeness of extraction and time. Milling roots to less than a 2 mm particle size, and using a sample size of 250 mg improved the recovery of resin and rubber but not of water extractables. This automated multi-solvent method improves the accuracy, repeatability and speed of the quantification of TK rubber, inulin and resins, and thereby the assessment of breeding strategies and processing.

Regulation of Natural Rubber Biosynthesis by Proteins Associated with Rubber Particles

Natural rubber, cis-1,4-polyisoprene, is an essential raw material used in thousands of products, many of which are absolutely necessary for medical purposes. Natural rubber is obtained from latex, an aqueous emulsion present in the laticiferous vessels of the natural rubber-producing plants. Hevea brasiliensis (the Brazilian rubber tree) currently is the only commercially important source of natural rubber. H. brasiliensis crops have very little genetic variability, leaving rubber plantations at risk of serious pathogenic attacks. In addition, repeated exposure to residual proteins in latex products derived from H. brasiliensis have led to serious and widespread allergic (type I) hypersensitivity. Therefore, identification of alternative sources of natural rubber is a very important biotechnological task. Potentially, Russian dandelion (Taraxacum kok-saghyz) may be such an alternative because significant amounts of natural rubber are produced in its root system. However, H. brasiliensis is a more efficient producer of natural rubber than T. kok-saghyz. Thus, improvement of rubber biosynthesis in plants is a first-priority problem of modern biotechnology. In this review, we describe proteins that may increase the concentration of natural rubber in laticiferous vessels of T. kok-saghyz and its close relative Taraxacum brevicorniculatum, when overexpressed in the plants. These proteins, cis-prenyltransferases, rubber transferase activator, and small rubber particle proteins, are directly involved in synthesis of the polyisoprene chain. We also analyze the effects of their expression levels on the production of natural rubber in vivo.

РАЗРАБОТКА ТЕХНОЛОГИИ КУЛЬТИВИРОВАНИЯ РАСТЕНИЙ ТАУ-САГЫЗА (Scorzoneratau-saghyzLipsch. etBosse) С ИСПОЛЬЗОВАНИЕМ ПОЧВЕННОЙ МИКРОФЛОРЫ: 4. МИКОРИЗАЦИЯ В УСЛОВИЯХ ЛАБОРАТОРНОГО ЭКСПЕРИМЕНТА

Scorzonera tau-saghyz - endemic of Kazakhstan, capable of accumulate up to 40% of rubber in dry roots and quality is not inferior to rubber hevea. Currently, research work is underway to restore the number of this species, as well as to develop effective and cost-effective biotechnologies for obtaining commercial rubber from the roots of the tau-saghyz. In long-term laboratory experiment carried out mycorrhization of seedlings. As inoculum used fungi Claroideoglomus etunicatum (Schüssler/Walker), Claroideoglomus claroideum (Schüssler/Walker) and Rhizophagus intraradices (Schüssler/Walker). In the roots of infected plants were revealed structures typical for fungi, forming arbuscular mycorrhizae type: non septate mycelium, vesicles and arbuscules. Mycorrhizal infection in the studied samples of S. tau-saghyz roots was 100 %. Infected plants was noticeably better than non-mycorrhizal. The average height and number of leaves of mycorrhizal plants was 1.5 times higher than that of non-mycorrhizal plants, which is proof of the importance of arbuscular mycorrhizae in the life of stenotopic, rare and extinct S. tau-saghyz. The use of endomycorrhizal fungi can significantly contribute to the development of modern, cost-effective biotechnologies aimed at restoring the abundance in nature and obtaining commercial rubber from the roots of tau-saghyz. These studies are particularly relevant at growing demand in the world for natural rubber and the search for alternative sources of natural rubber, in contrast to Hevea. Key words: Scorzonera tau-saghyz Lipsch. et G.G. Bosse, Glomeromycota, Claroideoglomus etunicatum (Schüssler/Walker), Rhizophagus intraradices (Schüssler/Walker), Claroideoglomus claroideum (Schüssler/Walker).

A century of guayule: Comprehensive genetic characterization of the US national guayule (Parthenium argentatum A. Gray) germplasm collection

The fragility of a single-source, geographically concentrated supply of natural rubber, a critical material of the modern economy, has brought guayule (Parthenium argentatum A. Gray) to the forefront as an alternative source of natural rubber. The improvement of guayule for commercial-scale production has been limited by the lack of genomic tools and well-characterized genetic resources required for genomics-assisted breeding. To address this issue, we developed nearly 50,000 single-nucleotide polymorphism (SNP) genetic markers and genotyped 69 accessions of guayule and its sister taxa mariola (Parthenium incanum Kunth), representing the entire publically available US national germplasm collection. We identified multiple interspecific hybrid accessions previously considered guayule, including five guayule-mariola hybrids and non-mariola interspecific hybrid accessions AZ-2 and AZ-3, two commonly used high-yielding cultivars. We dissected patterns of genetic diversity within the collection to identify a highly diverse subset of guayule accessions, and showed that wild guayule stands in Big Bend National Park, Texas, USA have the potential to provide hitherto untapped guayule genetic diversity. Together, these results provide the most thorough genetic characterization of guayule germplasm to date and lay the foundation for rapid genetic improvement of commercial guayule germplasm.

Genome analysis of Taraxacum kok-saghyz Rodin provides new insights into rubber biosynthesis

The Russian dandelion Taraxacum kok-saghyz Rodin (TKS), a member of the Composite family and a potential alternative source of natural rubber (NR) and inulin, is an ideal model system for studying rubber biosynthesis. Here we present the draft genome of TKS, the first assembled NR-producing weed plant. The draft TKS genome assembly has a length of 1.29 Gb, containing 46 731 predicted protein-coding genes and 68.56% repeats, in which the LTR-RT elements predominantly contribute to the genome enlargement. We analyzed the heterozygous regions/genes, suggesting its possible involvement in inbreeding depression. Through comparative studies between rubber-producing and non-rubber-producing plants, we found that enzymes of the mevalonate (MVA) pathway and rubber elongation might be critical for rubber biosynthesis, and several key isoforms have been isolated and shown to be predominantly expressed in the latex, indicating their crucial functions in rubber biosynthesis. Moreover, for two important families in rubber elongation, the CPT/CPTL and REF/SRPP families, diverse evolutionary tracks have been revealed. These results provide valuable resources and new insights into the mechanism of NR biosynthesis, and facilitate the development of alternative NR-producing crops.

Taraxacum kok-saghyz (TK): compositional analysis of a feedstock for natural rubber and other bioproducts

Abstract Natural rubber (NR) is a critical raw material primarily produced in Asia from a single plant species ( Hevea brasiliensis ). This lack of biologic and geographic diversity, coupled with increasing demand, makes it imperative that alternative sources of NR are developed. Taraxacum kok-saghyz (TK) is a rubber-producing dandelion being developed as an alternative to the traditional source of NR. In order to improve the value of this crop and make it competitive with other sources of NR, germplasm improvement, crop production optimization, efficient extraction and purification methods and the valorization of TK co-products are needed. In this study, a compositional analysis of field-grown TK roots was conducted in which total solids, ash content, protein, crude fat, fatty acids, carbohydrates, lignin, and total water-, acetone-, and hexane-extract (rubber) were quantified and characterized. Mass closure was greater than 95%. The analysis showed that 5.4% (g/g root dw) of the root consisted of rubber and 1.7% was acetone extractable (mainly sterols). Approximately 60% (g/g dw) of the root was hot water extractable. Soluble sugars (32%) and proteins (10%) were the most abundant water soluble fractions. Inulin (18%) and sucrose (10%) were the most abundant sugars. Insoluble components included cellulose 9% (glucan), hemicellulose 7% (xylan, mannan, arabinan, galactan), lignin 5%, protein 5% and pectin 3%. This compositional analysis provides a baseline which can be used to assess compositional changes induced by altering plant genetics, environmental conditions and cultivation practices. Based on these results, pathways for TK processing are proposed, and its potential as a biorefinery feedstock is evaluated. This analysis indicates that TK has potential as a source of not only NR but other products and/or raw materials of importance including inulin and proteins.

Guayule as an alternative source of natural rubber: A comparative life cycle assessment with Hevea and synthetic rubber

A comparative cradle-to-gate life cycle assessment (LCA) including raw material acquisitions, rubber production and transportation of synthetic rubber (SBR) and two natural rubbers, namely imported Hevea and US-grown guayule, was conducted to quantify environmental impacts and to identify area(s) of environmental improvement. The use of co-products from the two natural rubbers as a source of energy was explored for their impacts and energy offset potential. Three environmental impact categories-ozone depletion (ODP), global warming (GWP), and acidification potential (AP)-and net energy were evaluated.Results indicated that guayule rubber had a lower ODP impact compared to SBR, and lower GWP and AP impacts compared to Hevea rubber. The Hevea rubber production with biodiesel co-product from seed oil scenario had the highest GWP and AP impacts, whereas guayule rubber production with bio-oil co-product from bagasse had the highest ODP impact. Only the scenario of Hevea rubber production with biodiesel production indicated an overall energy production of 3.25 MJ/kg rubber, whereas all other scenarios indicated a net energy consumption. However, co-products contributed to reduction in total energy consumed in every scenario that was investigated. The most promising guayule rubber scenario among the six examined was that with electricity production from bagasse, as it contributed the least to all three impact categories and yielded the most net energy. Sensitivity analysis on this most promising guayule scenario indicated rubber yield, water use and electricity for water pumping in guayule irrigation as the key parameters that have significant impacts on results.