Reaction of gum arabic samples with monoclonal antibodies directed to plant cell wall polymers in dot immunobinding

Certain plant cell wall constituents have been found in gum samples derived from Acacia trees, thus analytical techniques for the determination of these plant cell wall components in any media can be applied in the analysis of the physico-chemical properties of these gums. In this experiment, gum samples harvested from various Acacia trees grown in different African countries were subjected to a dot immunobinding reaction using a panel of anti-plant cell wall directed monoclonal antibodies since the gum samples have been found to contain certain plant cell wall constituents. Five antiplant cell wall monoclonal antibodies, JIM 5, JIM 7, JIM 13, LM 6 and MAC 207 were reacted with fifteen gum Arabic samples 1 – 15 and water as control. The results showed that apart from reacting with the monoclonal antibodies, gum samples showed varying degrees of reactivity with the monoclonal antibodies. JIM 5 indicated no reaction with any of the gum samples, whereas JIM 7, JIM 13, LM 6 and MAC 207 exhibited reactions with the samples. The results suggest that, anti-plant cell wall directed monoclonal antibodies can be used as a tool to distinguish between gum Arabic samples from different tree species, as well as from different African countries. Thus, a testing kit which is easy to use and cheaper to acquire can be developed using anti-plant cell wall monoclonal antibodies, to improve quality control in the current gum trade

Characterisation and molecular association of Nigerian and Sudanese Acacia gum exudates

The chemical and physicochemical characteristics of gum exudate samples harvested from mature trees of Acacia senegal at two new specific ecolocations in Nigeria, have been investigated together with gum samples harvested from A. senegal and A. seyal originating from Sudan. The monosaccharide sugar compositions for the A. senegal gum samples were found to be similar, but the protein contents for the Nigerian samples were significantly higher than recorded for the Sudanese sample. Gel Permeation Chromatography coupled to light scattering, refractive index and U.V. detectors, has shown the presence of arabinogalactan, arabinogalactan–protein and glycoprotein fractions within the A. senegal gums and has also shown the presence of an additional small proportion of very low molar mass proteinaceous material all the samples which has previously been ignored. The plot of radius of gyration, Rg, as a function of elution volume showed a discontinuity for one of the Nigerian samples and for the A. seyal gum sample at elution volumes corresponding to the AGP component suggesting a different molecular structure. Plots of Mw–v–Rg confirmed that the molecules had a compact structure. The hydrodynamic size of the molecules was followed using dynamic light scattering as a function of time and it was found that molecular association occurred in solution. The extent of association increased as the protein content in the sample increased and was inhibited in the presence of electrolyte, it was concluded that association was due to electrostatic interaction between the protein moieties and glucuronic acid groups on individual macromolecules

Molecular characteristics, association and interfacial properties of Gum Arabic harvested from both Acacia Senegal and Acacia seyal

The molecular composition of Acacia senegal and Acacia seyal gum exudate samples were studied using transmission electron microscopy. The molecules observed in both samples were found to have diameters of either ~ 20μm, ~60 μm or ~ 10μm. These most likely represent the arabinogalactan (AG), arabinogalactan-protein (AGP) and glycoprotein (GP) molecules present in Acacia gum exudates. Micrographs obtained for gum solutions that had been left to stand for up to 5 days indicated that molecular aggregation had occurred, this was particularly evident for the Acacia senegal sample. This aggregation process was attributed to intermolecular electrostatic interactions. The adsorbed layer thickness of the gums adsorbed onto polystyrene latex particles was determined using dynamic light scattering. For the Acacia senegal gum sample, it was found that the adsorbed layer thickness increased over time and after 14 days had a value of 61nm. These findings are indicative of multilayer adsorption, through intermolecular electrostatic interaction. For the Acacia seyal gum sample the adsorbed layer thickness was only ~3nm and did not increase over time. Transmission electron microscopy revealed the presence of a distinct, thick adsorbed layer for the Acacia senegal gum and the presence of a much thinner, more diffuse layer for the Acacia seyal gum sample. Emulsification studies showed that the Acacia Senegal gum was more effective at stabilising limonene oil-in-water emulsions than the Acacia seyal sample and that this was because markedly more Acacia senegal gum adsorbed at the oil-water interface compared to the Acacia seyal gum exudate