Moringa oleifera seed protein isolate as an alternative for purifying turbid water

The Moringa oleifera oil industries extract oil from the seeds, the de-oiled M. oleifera seed meal (DMSM)
thus produced is discarded as waste. In the current study, DMSM was used to prepare M. oleifera
seed protein isolate (MPI). The coagulation ability of MPI to remove turbidity in synthetic turbid
water (STW), as well as real mud water (RMW), was evaluated. The results of the jar test, particle size
analysis and scanning electron microscopy with STW proved MPI to be a good coagulant. The MPI
reduced the turbidity in STW by more than 97% at a very low concentration (15 mg L–1). Further, the
coagulation efficiency of MPI in RMW was also evaluated. A comparative study demonstrated that
both MPI and aluminum sulfate (alum) could reduce >97% of the turbidity at the same concentration
(15 mg L–1). An increase of pH in MPI treated RMW from 6.9 to 7.1 and a significant decrease of pH
in alum treated RMW from 6.9 to 5.8 suggested that usage of lime and soda ash could be avoided for
increasing pH after MPI treatment unlike alum treated municipal water. MPI being a natural coagu-
lant, showed a marginal decrease from 1 to 0.5 mg L–1 in the chemical oxygen demand. The minimum
inhibitory concentration and minimum bactericidal concentration values for MPI were found to be 1
and 2 mg mL–1 respectively against Escherichia coli (ATCC 25922 – American Type Culture Collection,
Virginia, USA). These results suggested that, in place of alum, MPI can be used as a cost-effective,
natural, water treating agent in regions where people cannot afford clean and safe water.