Kinetics of chlorite dismutase in a perchlorate degrading reactor sludge

Abstract

Kinetics of chlorite dismutase (CD), the terminal enzyme involved in the perchlorate (ClO4(-)) reduction pathway, in a ClO4(-)-degrading bioreactor are reported in this study. Enzyme activity was determined from dissolved oxygen released during disproportionation of chlorite (ClO2(-)). CD activity was in the range 29.8-36.4 U/mg dry weight sludge, and kinetic constants Vmax and K(m) of the enzyme were 37.83 U/mg dry weight and 0.28 mM, respectively. Among reactor operational conditions, enzyme activity was observed at pH 4.0-9.0, with an optimum at pH 6.0. Redox potential in the range -50 to +120mV and NaCl up to 3.5 g/L had no significant effect on CD activity. However, co-occurring pollutants such as ammonium at 10 ppm, nitrite at 50 ppm and EDTA at 100 microM reduced CD activity substantially. The present study highlights ideal bioreactor conditions to avoid ClO2(-) toxicity, while indicating the buffering potential of a mixed microbial system against inhibiting factors to maintain stable CD activity in bioreactors.

Chlorate and Other Oxychlorine Contaminants Within the Dairy Supply Chain

“…DPRBs are capable of oxychlorine reduction and produce harmless chloride ions and, thus, have been identified as a potential method of remediating oxychlorine contamination (Coates & Achenbach, ). However, this method of perchlorate reduction from consumables is not viewed favorably by the public as microorganisms are involved in the treatment process (Vijaya Nadaraja, Gangadharan Puthiya Veetil, Vidyadharan, & Bhaskaran, ).…”