Fractionation of Leucaena seed-kernel proteins based on their solubility characteristics

Abstract

Leucaena leucocephala seeds were found to be rich in proteins, but they contained a toxic amino acid, mimosine. Protein-isolation processes rendered the seed proteins relatively free of anti-nutritional factors. Proteins of L. leucocephala (K8) seed kernels were separated into different fractions on the basis of their solubility, by extracting successively and directly, with various solvents, i.e. water, sodium chloride (5%), and sodium hydroxide (0·05 m). Globulins were found to be the major proteins, followed by albumins, glutelins, and prolamins. The proteins in these fractions were further precipitated, after determining their isoelectric points (pH 2–2·5). The protein and mimosine contents of the soluble extracts (before protein precipitation) and their isoelectric protein precipitates, supernatants, and insoluble residues, were determined. Sodium chloride (5%) was found to be the solvent of choice, since it resulted in maximum protein yield. Furthermore, most of the extracted mimosine was left in the supernatant after the protein had been precipitated out.