Perchlorate reduction using free and encapsulated Azospira oryzae enzymes.
Existing methods for perchlorate remediation are hampered by the common co-occurrence of nitrate, which is structurally similar and a preferred electron acceptor. In this work, the potential for perchlorate removal using cell-free bacterial enzymes as biocatalysts was investigated using crude cell lysates and soluble protein fractions of Azospira oryzae PS, as well as soluble protein fractions encapsulated in lipid and polymer vesicles. The crude lysates showed activities between 41 700 to 54 400 U L(-1) (2.49 to 3.06 U mg(-1) total protein). Soluble protein fractions had activities of 15 400 to 29 900 U L(-1) (1.70 to 1.97 U mg(-1)) and still retained an average of 58.2% of their original activity after 23 days of storage at 4 °C under aerobic conditions. Perchlorate was removed by the soluble protein fraction at higher rates than nitrate. Importantly, perchlorate reduction occurred even in the presence of 500-fold excess nitrate. The soluble protein fraction retained its function after encapsulation in lipid or polymer vesicles, with activities of 13.8 to 70.7 U L(-1), in agreement with theoretical calculations accounting for the volume limitation of the vesicles. Further, encapsulation mitigated enzyme inactivation by proteinase K. Enzyme-based technologies could prove effective at perchlorate removal from water cocontaminated with nitrate or sulfate.
Department of Civil and Environmental Engineering, University of Illinois , Urbana, Illinois 61801, United States.
Justin M
JM
Hutchison
Sean K
SK
Poust
Manish
M
Kumar
Donald M
DM
Cropek
Irene E
IE
Macallister
Clint M
CM
Arnett
Julie L
JL
Zilles
D001426:Bacterial Proteins / Q000378:metabolism*; D002852:Chromatography, Ion Exchange; D003124:Colorimetry; D060766:Drinking Water / Q000032:analysis; D010088:Oxidoreductases / Q000378:metabolism*; D010472:Perchlorates / Q000378:metabolism*; D043362:Rhodocyclaceae / Q000201:enzymology*; D014874:Water Pollutants, Chemical / Q000378:metabolism*; D018508:Water Purification / Q000379:methods*
D001426:Bacterial Proteins; D060766:Drinking Water; D010472:Perchlorates; D014874:Water Pollutants, Chemical; D010088:Oxidoreductases; C402794:chlorite dismutase; C021777:chlorate reductase; C494474:perchlorate