A Bacillus sphaericus Based Biosensor for Monitoring Nickel Ions in Industrial Effluents and Foods

A microbial-based biosensor has been developed based on enzyme inhibition bioassay for monitoring the presence of Ni(II) in real-time samples. The sensing element is immobilized Bacillus sphaericus MTCC 5100 yielding urease enzyme. The transducer is an NH4+ ion selective electrode in conjunction with a potentiometer. Heavy metals are potentially toxic to human beings. Nickel is associated with causing adverse health effects such as dermatitis and vertigo, in humans. Toxicity is manifested by affecting T-cell system and suppressing the activity of natural killer cells. Nickel finds applications in electroplating, coinage, electrodes, jewellery, alloys. The foods rich in Ni(II) are nuts, beans, oats, and wheat. The range of Ni(II) detection by the developed biosensor is 0.03-0.68 nM (0.002-0.04 ppb) with a response time of 1.5 minutes. For application, the Ni(II) effluent was procured from an electroplating industrial unit and was found to have a concentration of 100.0 ppm Ni(II). In foods, wheat flour sample was acid digested and Ni(II) was specifically complexed in the presence of other cations, and had an Ni(II) concentration of 0.044 ppm. The developed system has a reliability of 91.5% and 90.6%, respectively, for the samples and could possibly replace the existing conventional techniques of analysis.