Fractionation and Properties of Oocystis Algal Proteins

Abstract

Proteins of the alga Oocystis were fractionated, characterized and compared for their composition and functional properties plus the effect of succinylation. Extraction of Oocystis proteins by successive ammonium sulphate fractionation yielded 44% and 66% protein in the absence or presence of ascorbic acid and polyvinylpyrrolidone, respectively, indicating that the presence of oxidative enzymes and phenolic compounds may partially impair the recovery of algal proteins. Both sedimentation, velocity ultracentrifugation and electrophoretic analyses indicated that most of the algal extract proteins were of a single type (1.2S; 12,500 daltons) with the 30% fraction having higher levels of threonine, methionine and cystine.The protein contents of the various preparations ranged from 71% (ethanol fraction) to 96% (succinylated fraction). Ribonucleic acid (RNA) content in most protein preparations ranged from 6.1% (whole protein fraction) to 11.1% (isoelectric point fraction) with the concentration of lysine, leucine, valine, phenylalanine and tyrosine being high in six of the preparations. In general, except for ethanol precipitated protein, Oocystis protein samples showed good fat absorption, foaming and emulsion capacities and were soluble above pH 6.0. Ethanol precipitated proteins had a high ash content and showed good water absorption but poor emulsion capacities.There was a major reduction in RNA content (1.9%) and improvement in the solubility, water absorption, foaming capacity and viscosity by succinylation, but this process led to poor foam stability and thickening properties upon heating.The protein samples isolated from Oocystis are white and have a bland taste; these properties should permit the fortification of other foodstuffs with relatively little effect on palatability.