Date : 08- February-2022a Novel Gas Production Bioassay of Thiosulfate Utilizing Denitrifying Bacteria (Tubd) for the Toxicity Assessment of Heavy Metal Contaminated Water

This study reports for the first-time the possibility of deploying gas production by thiosulfate utilizing denitrifying bacteria (TUDB) as a proxy to evaluate water toxicity. The test relies on gas production by TUDB due to inhibited metabolic activity in the presence of toxicants. Gas production was measured using a bubble-type respirometer. Optimization studies indicated that 300 mg [[EQUATION]] N/L, 0.5 mL acclimated culture, and 2,100 mg S 2 O 3 2- /L were the ideal conditions facilitating the necessary volume of gas production for sensitive data generation. Determined EC 50 values of the selected heavy metals were: Cr 6+ , 0.51 mg/L; Ag + , 2.90 mg/L; Cu 2+ , 2.90 mg/L; Ni 2+ , 3.60 mg/L; As 3+ , 4.10 mg/L; Cd 2+ , 5.56 mg/L; Hg 2+ , 8.06 mg/L; and Pb 2+ , 19.3 mg/L. The advantages of this method include operational simplicity through the elimination of cumbersome preprocessing procedures which are used to eliminate interferences caused by turbidity when the toxicity of turbid samples is determined via spectrophotometry