by David A Ramirez‐Cadavid, Katrina Cornish, Upul Hathwaik, Robert Kozak, Colleen McMahan and Frederick C Michel Jr. (Journal of Chemical Technology and Biotechnology) Taraxacum 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.
RESULTS
Enzymatic 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.
CONCLUSION
Enzymatic 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.
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In a previous study by our group, compositional analysis of TK NR contaminants revealed that 77% w/w of the dirt fraction in Eskew extracted rubber consisted of cell wall components: cellulose (27%), hemicellulose (21%), lignin (15%), and pectin (14%). … Research on the conversion of lignocellulosic biomass to bioethanol has led to the development of several peocesses that disrupt and solubilize these structural carbohydrates and lignin. … Most of these processes incorporate mechanical, chemical and/or biological pretreatments to initially weaken the plant cell wall followed by enzymatic treatment with hydrolases to depolymerize cell wall carbohydrates to sugar oligomer and monomers. …
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Recently, our group developed an aqueous, enzyme-based method for the separation and purification of TK rubber as part of the Program for Excellence in Natural Rubber Alternatives that significantly improved the yield and purity of TK rubber compared to the Eskew process.
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Pectinase was added at the recommendation of Atlantic Biomass LLC based on their work on biomass conversion to biofuel.
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Alkaline pretreatment prior to enzymatic hydrolysis has been previously shown to improve lignocellulosic hydrolysis…. Consistent with this, the treatments that included alkaline pretreatment (A) followed by enzyme digestion (E) had significantly higher rubber yields than those without pretreatment. Treatments including enzyme digestion (E) also had smaller non-rubber (bagasse) particles … which may improve rubber separation from bagasse by centrifugation.
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Otherwise, new treatments that complement those developed in this study, such as biologial degradation of TN NR contaminants by microorganisms and/0r ligninolytic enzymes should be investigated. Further research to evaluate the scale up potential, economic feasibility, and processes by byproduct valorization for these processes is also needed. READ MORE