title: 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.
authors.affiliation: Environmental Technology, CSIR-National Institute for Interdisciplinary Science & Technology, Thiruvananthapuram-19, India.
authors.forename: Anupama Vijaya
authors.initials: AV
authors.lastname: Nadaraja
authors.affiliation: Environmental Technology, CSIR-National Institute for Interdisciplinary Science & Technology, Thiruvananthapuram-19, India.
authors.forename: Prajeesh Gangadharan Puthiya
authors.initials: PG
authors.lastname: Veetil
authors.affiliation: Environmental Technology, CSIR-National Institute for Interdisciplinary Science & Technology, Thiruvananthapuram-19, India.
authors.forename: Athira
authors.initials: A
authors.lastname: Vidyadharan
authors.affiliation: Environmental Technology, CSIR-National Institute for Interdisciplinary Science & Technology, Thiruvananthapuram-19, India.
authors.forename: Krishnakumar
authors.initials: K
authors.lastname: Bhaskaran
mesh_terms: D064751:Ammonium Compounds / Q000737:chemistry; D019149:Bioreactors; D004492:Edetic Acid / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009573:Nitrites / Q000737:chemistry; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D010472:Perchlorates / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism*; D012722:Sewage; D012965:Sodium Chloride / Q000737:chemistry; D014877:Water Pollution, Chemical; D018508:Water Purification / Q000379:methods*
chemical_list: D064751:Ammonium Compounds; D009573:Nitrites; D010472:Perchlorates; D012722:Sewage; D012965:Sodium Chloride; D004492:Edetic Acid; D010088:Oxidoreductases; C402794:chlorite dismutase; C494474:perchlorate