The use of natural coagulant protein in drinking water treatment has been discussed for a long time, though the method is still not in practice, probably due to limited knowledge and availability of material. In the present work, different Mustard varieties were tested for the presence of coagulant protein compared with Moringa seed extract and their potential application in water treatment. The coagulation activity of the protein extract was measured using synthetic clay solution as well as water from pond. The protein content was determined by Bradford method, molecular mass determined by Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and peptide sequence was analyzed by Mass spectrometry. Extract of Mustard (large) and Moringa seed showed coagulation activity of %70 and %85 % after 90 min, respectively. Interestingly, seed extracts from other Mustard varieties had coagulation activity after heat activation at 95°C for 5 h. However, the coagulation activity of Mustard seed extract against turbid pond water was higher (%60 %) compared to Moringa seed extract (%50 %). The peptide sequence analysis of 6.5 and 9 kDa proteins was found to be homologous to Moringa coagulant protein and napin3, respectively. To our knowledge, this could be the first report on Mustard seed having coagulant protein. The coagulation activity of Mustard (large) against highly turbid pond water suggested that it could be a potential natural coagulant for water treatment.

Access to fresh water is limited due to the growing population and to provide safe drinking water is a global challenge. In this initial study, about a hundred different samples were screened for coagulation activity. Amongst the plants tested were fruits and vegetable pulps, leaves and seeds (like jackfruit, tamarind, papaya, orange, watermelon, pineapple, cucumber, green gram, peas, black gram, cluster bean rice, maize, chili, cabbage, mustard, cauliflower, beetroot and carrot). The crude extracts were prepared in water and salt solution in order to extract the coagulant protein and compare the coagulation activity. Among the tested samples, only a few seed extracts showed coagulation activity. The seed extracts of mustard and cabbage showed coagulation activity in both water and salt extracts and were comparable to that of Moringa seed extract. The salt extracts showed higher activity compared to that of water extract in most of the samples tested. The coagulation activity was stable after incubation at 95 °C for 5 hours implying heat resistance. A protein profile analysis showed major protein bands with a molecular weight around 6.5 and 9 kDa. In this preliminary study, mustard and cabbage seed extracts were promising in terms of coagulation and heat resistance, so could be an alternative to Moringa seed for water treatment and should be investigated further.