A Potentiometric Biosensor for Cyanide Detection using Immobilized Whole Cell Cyanide Dihydratase of Flavobacterium indicum MTCC 6936

Abstract

A potentiometric biosensor for cyanide detection has been developed using whole cell cyanide dihydratase activity of Flavobacterium indicum coupled to an ammonium ion selective electrode. The cyanide dihydratase activity was optimum when 2% agar and cells in the amount of 0.175 mg/mL dry cell weight (dcw) were used for immobilization. The free and immobilized whole cell cyanide dihydratase of F. indicum exhibited maximum activity (0.192 U/mg dcw and 0.175 U/mg dcw, respectively) in 0.1 M sodium phosphate buffer (pH 8.0) at 35°C with 5 mM potassium cyanide. K_M and V_max for free and immobilized whole cell cyanide dihydratase were 5.25 mM, 0.33 U/mg dcw and 6.25 mM, 0.25 U/mg, respectively. The agar immobilized whole cell cyanide dihydratase was used as a biocomponent coupled to a potentiometer. A linear relationship was observed between response time and cyanide concentration. The cyanide concentration of 0.06 ppm could be detected using this potentiometric biosensor with a response time of 2 min. The developed potentiometric biosensor could be used for the detection of cyanide in industrial wastewater and food samples.