Interactions of surfactants with a water treatment protein from Moringa oleifera seeds in solution studied by zeta‐potential and light scattering measurements

Abstract

Protein extracted from Moringa oleifera (MO) seeds has been advocated as a cheap and environmental friendly alternative to ionic flocculants for water purification. However, the nature and mechanism of its interaction with particles in water, as well as with dissolved surface-active molecules, are not well understood. In this article, we report studies of the protein and its interaction with four surfactants using dynamic light scattering (DLS), zeta-potential and turbidity measurements. Zeta-potential measurements identified points of charge reversal and the turbidity and DLS measurements were used to characterize the microstructure and size of protein-surfactant complexes. From the points of charge reversal, it was estimated that 7 anions are required to neutralize the positive charges of each protein molecule at pH 7. For protein mixtures with sodium dodecyl sulfate and dodecyl di-acid sodium salt, the peak in turbidity corresponds to concentrations with a large change in zeta-potential. No turbidity was observed for protein mixtures with either the nonionic surfactant Triton X-100 or the zwitterionic surfactant N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate. Changes of pH in the range 4-10 have little effect on the zeta-potential, turbidity, and the hydrodynamic radius reflecting the high isoelectric point of the protein. Addition of small amounts of salt has little effect on the size of protein in solution. These results are discussed in the context of the use of the MO protein in water treatment.

Interactions of bovine serum albumin with cationic imidazolium and quaternary ammonium gemini surfactants: Effects of surfactant architecture

“…The interaction between protein and surfactant is an active field of research interest, which is of great importance in biological, pharmaceutical, and cosmetic industries [10][11][12][13]. Based upon our earlier studies on the imidazolium gemini surfactants [C n -4-C n im]Br 2 [49][50][51][52], in this work, we have investigated comparatively that the BSA interacts with cationic gemini surfactants with imidazolium and quaternary ammonium groups, and their corresponding monomers via fluorescence probe technique of pyrene, circular dichroism, synchronous fluorescence, and UV-visible absorption spectra.…”

“…The investigations of the native proteins are not only useful for their immense potential in applications but also providing an intellectual challenge [1][2][3][4]. Studying of protein/surfactant interaction is an active field of interest over the past decades, ever since surfactants are known to interact with proteins thereby inducing polarity and stability changes of proteins [5][6][7][8][9], which is of great importance in biological, pharmaceutical, and cosmetic systems [10][11][12][13]. For example, anionic surfactants are widely used for the determination of molecular weights of proteins or size separation by electrophoresis [14].…”

The use of Moringa oleifera seeds and their fractionated proteins for Microcystis aeruginosa and microcystin‐LR removal from water

“…According to Kwaambwa and Rennie, proteins are amphoteric polymers. In general, the positive charges in an acidic medium are determined by protonation of NH 2 groups in arginine side chains, asparagines, and glutamine, while the negative charges are the result of COOH group dissociation in glutamic and aspartic acid side chains in alkaline media.…”

Surface Activity Interactions in Aqueous Solution of Anionic Surfactants with a Water Treatment Protein from <i>Moringa oleifera</i> Seeds

“…Previously Kwaambwa and Rennie [18] studied the effect of SDS concentration on the zeta potential (ζ) of the MO protein in aqueous solution. The zeta potential was used to identify the points of charge reversal in the solutions.…”