Development of an automated water toxicity biosensor using Thiobacillus ferrooxidans for monitoring cyanides in natural water for a water filtering plant.
An on-line biosensor consisting of immobilized Thiobacillus ferrooxidans and an oxygen electrode was developed for automated monitoring of acute toxicity in water samples. T. ferrooxidans is an obligatory acidophilic, autotrophic bacterium and derives its energy by the oxidation of ferrous ion, elemental sulfur, and reduced sulfur compounds including metal sulfides. The assay is based on the monitoring of a current increase by addition of toxicoids, which is caused by the inhibition of bacterial respiration and decrease in oxygen consumption. Optimum cell number on the membrane was 5.0 x 10(8) cells. The steady-state current was obtained when concentration of FeSO4 was above 3.6 mM at pH 3. The sensor response of T. ferrooxidans immobilized membrane for 5.0 microM KCN was within an error of 10% for 30 membranes. A linear relationship was obtained at KCN concentration in the range of 0.5-3.0 microM in a flow-type monitoring system. Minimum detectable concentrations of KCN, Na2S, and NaN3 were 0.5, 1.2, and 0.07 microM, respectively. The monitoring system contained two biosensors and these sensors were cleaned with sulfuric acid (pH 1.5) twice a day. This treatment could remove fouling on microbial immobilized membrane by natural water and ferrous precipitation in the flow cell. This flow-type monitoring sensor was operated continuously for 5 months. Also, T. ferrooxidans immobilized membrane can be stored for one month at 4 degrees C when preserved with wet absorbent cotton under argon gas.
Okochi
Mina
M
Department of Biotechnology and Life Sciences, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, 184-8588, Japan.
Mima
Koji
K
Miyata
Maki
M
Shinozaki
Youhei
Y
Haraguchi
Satoshi
S
Fujisawa
Minoru
M
Kaneko
Masao
M
Masukata
Tadashi
T
Matsunaga
Tadashi
T
D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D018914:Cells, Immobilized; D003486:Cyanides / Q000032:analysis* / Q000633:toxicity*; D004563:Electrochemistry / Q000295:instrumentation* / Q000379:methods; D004867:Equipment Design; D019544:Equipment Failure Analysis; D017022:Flow Injection Analysis / Q000295:instrumentation*; D010100:Oxygen / Q000032:analysis / Q000378:metabolism; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013855:Thiobacillus / Q000187:drug effects* / Q000378:metabolism; D018675:Toxicity Tests / Q000295:instrumentation / Q000379:methods; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity; D018508:Water Purification / Q000379:methods; D014881:Water Supply / Q000032:analysis*
D003486:Cyanides; D014874:Water Pollutants, Chemical; D010100:Oxygen