Bio-based materials and related technologies have become of prime interest as society moves towards a sustainable world. For example the use of proteins in soybeans and their derivatives for multiple applications has evolved rapidly; especially their isolate fractions, as key biopolymer component in plastics, adhesives and composites. In order to expand the use of widely available proteins in soybean, glycinin and � conglycinin, the two major storage proteins in soybeans; we investigated their adsorption on cellulose and reference silica substrates by using quartz crystal microgravimetry with dissipation monitoring. Proteins were fractionated from soy flour, and different aqueous solution concentrations in pH 7 phosphate buffer were used to evaluate the effect of ionic strength and the presence of 10 mM of 2-mercaptoethanol as denaturant on the adsorbed amount. It was found that the adsorption on silica was affected by electrostatic interactions between the protein molecules and the surface; specifically, in the presence of salt the adsorption was higher and cooperative effects were observed as the concentration of protein was increased. On the other hand, denatured glycinin protein was adsorbed to a lower extent due to the unfolding of its structure that exposed hydrophobic groups of the molecule, thereby reducing the affinity with silica. Adsorption studies on ultrathin films of cellulose followed similar trends as those observed for silica; however, lesser adsorption was measured and the effect of salt was found to be more critical. It ishypothesized that this effect is due to the screening of electrostatic interactions between soy glycinin and the negatively charged cellulose. When in the presence of denaturant, adsorption on cellulosic films was only observed for the higher concentration of protein studied of 1 mg/ml, which suggest the lower affinity of denatured hydrophobic protein molecules for hydrophilic cellulosic surface.

Adsorption of soy glycinin onto silica and ultrathin cellulosic films studied by quartz crystal microgravimetry

241st National Meeting (2011)

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