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

Authors: RAMIREZ CAVIDAD, DAVID - The Ohio State University; Hathwaik, Upul; CORNISH, KATRINA - The Ohio State University; McMahan, Colleen; MICHEL JR., FRED - The Ohio State University

Submitted to: Biochemical Engineering Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2022
Publication Date: 2/22/2022
Citation: Ramirez Cavidad, D., Hathwaik, U.I., Cornish, K., McMahan, C.M., Michel Jr., F. 2022. Alkaline pretreatment of Taraxacum kok-saghyz (TK) roots for the extraction of natural rubber (NR). Biochemical Engineering Journal. 181. Article 108376. https://doi.org/10.1016/j.bej.2022.108376.
DOI: https://doi.org/10.1016/j.bej.2022.108376

Interpretive Summary: The plant species Taraxacum kok-saghyz, also known as Rubber Dandelion, is under development in the United states as a source of valuable natural rubber. Processes for extraction of natural rubber from plant tissues must recover the maximum amount of rubber while preserving the quality (molecular weight). The green processes described here use chopping, then combinations of water, base, heat, and enzymes, to soften plant tissues. High quality rubber can then be separated by filtration. Over 80% rubber yield was achieved using this process.

Technical Abstract: Natural rubber (NR) is an essential biological material, the supply of which is insecure. Taraxacum kok-saghyz (TK), a rubber-producing dandelion, is currently being developed as an alternative source of NR. Alkaline pretreatment of TK roots could potentially improve the yield of TK NR, but also negatively affect rubber quality, and has not previously been investigated. Alkaline pretreatments of TK roots were tested at sodium hydroxide loading rates of 33 to 132mg NaOH/g TK roots and temperatures of 25°C to 160°C, followed by enzymatic digestion with pectinase and cellulase. As NaOH loading rate and temperature increased, rubber yield increased from a low of 67.6% to a maximum of 82.6%, but rubber molecular mass and rubber gel content decreased. Rubber impurity content and thermal properties were unaffected by loading rate or temperature. The pooled mean of dirt contents among treatments was 2.6±0.4% w/w. The untreated control yielded 63.0% with a dirt content of 3.1±0.2% w/w. FTIR analysis indicated that alkaline pretreatment modified non-rubber components. SEM images revealed dramatic structural changes in embedded root tissues as a function of reaction temperature. In summary, alkaline pretreatment followed by enzymatic digestion is an efficient method to extract NR from TK roots. However, at temperatures above 120°C, and NaOH loadings roots, the process negatively impacts rubber quality.