In this study, a process for the removal of proteins from skim natural rubber latex (SNRL) was developed. This process involves a one-step incubation with urea in the presence of a surfactant and an organic solvent, followed by leaching. After 1 h of incubation in 0.1 wt% urea, 1 wt% sodium dodecyl sulfate (SDS) and 1% ethanol, the extractable protein (EP) content was lower than that of a deproteinized SNRL (D-SNRL) prepared via a single step. To further reduce the protein content, leaching with SDS coupled with 1–3 centrifugation cycles was performed. The EP content of D-SNRL with an additional leaching step and 3 centrifugation cycles under the optimum conditions was found to be 0.179 mg/g. Additionally, the nitrogen content, as determined by the Kjeldahl method, confirmed that the protein content was decreased to 0.053%, which was lower than those of the SNRL and D-SNRL samples processed in a single step. Fourier transform infrared spectra confirmed that the protein contents of these samples decreased with an increasing number of leaching steps. Thermogravimetric analysis showed quite similar thermal stability for the product of each deproteinization process. The tensile strength and elongation at breakage of the rubber film decreased after protein removal. Scanning electron microscopy revealed that all rubber films had quite smooth surfaces. This deproteinization method with an additional leaching step allowed for highly efficient protein reduction of up to 96%. This method is expected to improve the quality of skim latex products for several biomedical applications.
Keywords
Skim latex, Natural rubber, Deproteinization, Proteins, Rubber film