The effect of remaining SDS on protein release in later leaching steps of deproteinized natural rubber

Abstract

The effect of remaining sodium dodecyl sulfate (SDS) used in washing steps on further leaching of proteins from the deproteinized rubber films was investigated. High-Ammonia Natural Rubber Latex (HANRL) was diluted with 0.01% w/v potassium hydroxide solution to obtain about 30% dry rubber content (DRC) and it is called diluted NRL. The untreated NRL was directly casted to a film (sample 0). Sample 1 was prepared by centrifugation of diluted NRL at 5000 rpm for 1 min. Sample 1-2 was prepared by washing Sample 1 with 0.5%wt SDS solution. Sample 1-3 was prepared by washing Sample 1-2 with 0.1%wt SDS solution. After that they were casted into films. The dried films were checked for the extractable protein (EP) content by modified Lowry method and nitrogen content according to SMR: Bulletin No.7-1992. The EP content of Sample 1 film was less than the untreated (Sample 0) one but the EP content was increased after washing with 0.5%wt SDS solution and then dropped slightly after washing again with 0.1%wt SDS solution. In contrast, nitrogen content and FTIR spectra confirmed that the total amount of proteins in films was decreased when they underwent more treating steps. This finding suggested that although overall protein content decreased, the remaining SDS on the films could facilitate further leaching of EP from the film surface when it was in contact with extraction medium (PBS or synthetic sweat) under condition with shear force. The use of this deproteinized film should, therefore, be done with care.

Keywords

• Deproteinization
• Extraction
• Natural rubber latex
• Protein
• SDS