Proteins from common bean (Phaseolus vulgaris) seed as a natural coagulant for potential application in water turbidity removal.

The ability of coagulation active proteins from common bean (Phaseolus vulgaris) seed for the removal of water turbidity was studied. Partial purification of protein coagulant was performed by precipitation with ammonium sulphate, dialysis and anion exchange chromatography. Adsorption parameters for ion-exchange process were established using dialysate extract. Results revealed that the highest values of the adsorbed protein were achieved in 50 mmol/L phosphate buffer at pH 7.5 and the maximum adsorption capacity was calculated to be 0.51 mg protein/mL matrix. Partially purified coagulant at initial turbidity 35 NTU expressed the highest value of coagulation activity, 72.3%, which was almost 22 times higher than those obtained by crude extract considering applied dosages. At the same time, the increase in organic matter that remained in water after coagulation with purified protein coagulant was more than 16 times lower than those with crude extract, relatively to its content in blank. Copyright 2009 Elsevier Ltd. All rights reserved.