Enzymatic detection of As(III) in aqueous solution using alginate immobilized pumpkin urease: Optimization of process variables by response surface methodology

Urease immobilized on alginate was utilized to detect and quantify As³⁺ in aqueous solution. Urease from the seeds of pumpkin (vegetable waste) was purified to apparent homogeneity by heat treatment and gel filtration (Sephadex G-200). Further enzyme was entrapped in 3.5% alginate beads. Urea hydrolysis by enzyme revealed a clear dependence on the concentration and interaction time of As³⁺. The process variables effecting the quantitation of As³⁺ was investigated using central composite design with Minitab^® 15 software. The predicted results were found in good agreement (R² = 96.71%) with experimental results indicating the applicability of proposed model. The multiple regression analysis and ANOVA showed that enzyme activity decreased with increase of As³⁺ concentration and interaction time. 3D plot and contour plot between As³⁺ concentration and interaction time was helpful to predict residual activity of enzyme for a particular As³⁺ at a particular time.