Optimal conditions for deproteinizing natural rubber using immobilized alkaline protease

Abstract

BACKGROUND Natural rubber latex contains allergenic proteins. Therefore, processes for deproteinizing the latex are needed. An immobilized enzyme process for deproteinization is reported. An optimal protocol was first developed for immobilizing a protease on cellulose−chitosan composite beads. The beads were then used in developing an optimal deproteinization treatment. The main effects and the interactions of the factors for the two processes were identified using a two-level full factorial experimental design. RESULTS Under optimal conditions (15% cellulose in beads, immobilizing reaction pH of 9, immobilization period of 24 h), the beads attained the highest specific activity of 1685.3 U g−1 beads. Using these beads, the optimal conditions for deproteinization of the latex were: an enzyme loading of 0.1 parts per hundred of rubber (phr), a sodium dodecyl sulfate concentration of 20 phr, 30°C, and a treatment period of 12 h. The nitrogen content of the rubber was reduced to 0.012% from an initial value of 0.3%. The enzyme beads were operationally stable and could be reused for at least five cycles. CONCLUSIONS The optimized treatment effectively deproteinized the natural rubber. The final product was free of peptides. This deproteinization treatment was more effective than the conventional urea-based treatment performed for comparison. © 2014 Society of Chemical Industry