Effect of heat and pH on the carbohydrate epitopes of gum from Acacia senegal recognised by monoclonal antibodies

Abstract

Carbohydrate epitopes on the arabinogalactan protein (AGP) gum arabic recognised by a panel of seven monoclonal antibodies (MAbs), raised in a previous study, have been further characterised. These MAbs have now been divided into three groups based on their response to mild hydrolysis and elimination (neutral hydrolysis) when heated in buffers at different pH values. We have also investigated the binding of these antibodies to three fractions of gum arabic separated by hydrophobic interaction chromatography. MAb groups I and III produce consistent responses when tested against heat-treated whole and fractionated gum arabic, whilst group H display a varied response suggesting that these MAbs recognise complex epitopes, the structure of which is not immediately apparent. It appears that neutral hydrolysis is capable of increasing or decreasing the affinity of certain epitopes, whilst hydrolysis with a strong acid (TFA; tri-fluoro acetic acid) under harsh conditions reduces the affinity for all antigens. The results obtained have shown that the MAbs can be divided into three categories, two of which have distinctive and easily reproducible responses to treatment of the gum and would therefore be suitable for the investigation of Acacia gums which have been subjected to food preparation procedures.