The natural coagulant Moringa oleifera lectin (MoL) has coagulation efficiency comparable to that of aluminum sulfate and is more environmentally sustainable than the latter. The coagulation efficiencies of culture supernatants from 50 MoL-secreting colonies and a control lacking MoL secretion were compared by observing turbidity removal from a 600 NTU kaolin suspension. Remarkably, 80% of the tested supernatants showed more than 80% turbidity removal, down to less than 100 NTU, the level achieved with the control supernatant. The coagulation efficiency of the four colonies achieving the highest levels of turbidity removal (colonies 2, 29, 31, and 49) was tested in triplicate alongside a control sample using 200 NTU turbid water. The mean difference in turbidity removal between the four colonies and the control was found to be significant using Dunnett's test (P < 0.01). The secreted MoL from GS115/pPIC9/MoL colony 2, the most efficient MoL-producing colony (mean difference compared to control, 42%; P = 0.001), was purified using an N-terminal hexa-His-tag and Ni-NTA spin columns. The expression of MoL was confirmed by the presence of a single 8 kDa band using SDS-PAGE analysis. The recombinant MoL produced by Pichia pastoris was secreted, and possessed a coagulation capacity of 83%, as determined based on the reduction in turbidity of 400 NTU water.
Keywords: Lectin, Moringa oleifera, Natural coagulant, Pichia pastoris, Turbidity.