Isolation of napin from Brassica nigra seeds and coagulation activity to turbid pond water

Abstract

Approach to fresh water is limited due to the growing world population and supply of clean drinking water is a global challenge. Pond water is widely used for drinking in developing countries and it has higher turbidity during rainy seasons. This purpose requires a large number of chemical coagulants that lead to a high cost of treatment. Therefore there is a need to find an economical and natural coagulant to treat turbid water. Coagulation activity is an ability of a liquid, changing to a solid or semi-solid state after sometime period of time. This study focuses on the isolation of coagulant proteins from Brassica nigra seeds responsible for water clarification. The coagulant protein (napin) was purified, quantified and identified. Napin protein was precipitated with 70% saturation of ammonium sulfate solution combined with dialysis and size-exclusion chromatography. SDS-PAGE showed that isolated napin has a molecular weight of 16 kDa. Protein quantification was done by using a NanoDrop spectrophotometer. The coagulation activity of the napin protein was measured against synthetic clay solution and turbid pond water. The coagulation assay results showed that napin protein from Brassica nigra has 85% and Moringa seeds extract has 87% coagulation activity against the synthetic clay solution after 120 min. However, the coagulation activity of napin protein against the turbid pond water was higher 85% compared to Moringa seed extract of 80%. The active coagulant napin protein would be helpful in establishing cheaper methods in scaling up the coagulant protein from the Brassica nigra seeds acting as a potential agent for water treatment. HIGHLIGHTS A 16 kDa napin protein was isolated and purified from Brassica nigra seeds.; Napin protein was purified by using the Fast protein chromatography technique.; The N-terminal amino acid sequence showed 100% homology with Napin-3 of Brassica napus and isolated natural coagulant napin, a seed storage protein that showed coagulation activity against a synthetic kaolin solution and turbid pond water.;

Keywords

• brassica nigra
• coagulation
• napin protein
• seed
• sodium dodecyl sulfate–polyacrylamide gel electrophoresis (sds-page)