In this study, the serum phase of natural rubber latex was shown to contain proteins with molecular weight different from those of rubber particles. The proteins of serum phase were in regions of 6 to more than 200 kDa, while the major proteins of rubber particle were 14.5 and 29 kDa, which were similar to Rubber elongation factor and Hevamines, respectively. It was also found that enzymatic deproteinization could break down the protein linkages selectively and retained the oligopeptide groups associated to rubber molecules while saponification can remove both protein and phospholipid linkages. Characterization of the extracted associated phospholipids obtained from saponification treatment of dry AENR, were carried out by 1H-NMR spectroscopy and GC–MS and compared with a database of known molecules. The 1H-NMR spectrum of the extracts revealed major signals, which are assignable to ―(CH2)n―, ―CH2OP, ―CH2OC═O and ―OCH2CH2NH― and the appearance of these signals indicates that the serum contains phospholipids associated with the rubber chain. GC–MS analysis revealed that the composition of fatty acid ester groups associated with the NR molecule at the termini were saturated fatty acids including palmitic acid, stearic acid, lauric acid, myristic acid, and unsaturated fatty acids such as linoleic acid and linoleinic acid, which evidenced the presence of associated fatty acid in phospholipids. SEM and zeta potential analyses also showed that there are phospholipid–protein layers surrounding the surface of the rubber particles to stabilize colloidal of NR latex. After removal of the phospholipid–protein layers by deproteinization and saponification, a surfactant layer replaced the phospholipid-protein layers on the surface of rubber particles.
In this study, the serum phase of natural rubber latex was shown to contain proteins with molecular weight different from those of rubber particles. The proteins of serum phase were in regions of 6 to more than 200 kDa, while the major proteins of rubber particle were 14.5 and 29 kDa, which were similar to Rubber elongation factor and Hevamines, respectively. It was also found that enzymatic deproteinization could break down the protein linkages selectively and retained the oligopeptide groups associated to rubber molecules while saponification can remove both protein and phospholipid linkages. Characterization of the extracted associated phospholipids obtained from saponification treatment of dry AENR, were carried out by 1H-NMR spectroscopy and GC–MS and compared with a database of known molecules. The 1H-NMR spectrum of the extracts revealed major signals, which are assignable to ―(CH2)n―, ―CH2OP, ―CH2OC═O and ―OCH2CH2NH― and the appearance of these signals indicates that the serum contains phospholipids associated with the rubber chain. GC–MS analysis revealed that the composition of fatty acid ester groups associated with the NR molecule at the termini were saturated fatty acids including palmitic acid, stearic acid, lauric acid, myristic acid, and unsaturated fatty acids such as linoleic acid and linoleinic acid, which evidenced the presence of associated fatty acid in phospholipids. SEM and zeta potential analyses also showed that there are phospholipid–protein layers surrounding the surface of the rubber particles to stabilize colloidal of NR latex. After removal of the phospholipid–protein layers by deproteinization and saponification, a surfactant layer replaced the phospholipid-protein layers on the surface of rubber particles.
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