Aerobic cometabolism of chloroform by butane-grown microorganisms: long-term monitoring of depletion rates and isolation of a high-performing strain.
The focus of this microcosm study was to monitor the performances of 17 butane-utilizing microcosms during a long-term (100-250 days) aerobic cometabolic depletion of chloroform (CF). The depletion of the contaminant began after a lag-time variable between 0 and 23 days. All microcosms quickly reached a pseudo steady-state condition, in terms of biomass concentration (with an average of 9.3 x 106 CFU ml(-1)), chloroform depletion rate (5 micromol l(-1) d(-1)) and butane utilization rate (730 micromol l(-1) d(-1)). After about 100 days of CF depletion, a sudden 5- to 7-fold increase of the chloroform rate was observed in two microcosms, where the highest amount of contaminant had been depleted. In one of these high-performing microcosms, an experiment of chloroform depletion in the absence of butane resulted in the depletion of a surprisingly high amount of contaminant (765 micromolCF kg(-1) dry soil in 2 months) and in a marked selection of a single bacterial strain. Bioaugmentation assays conducted with the biomass selected in this microcosm and with a pure culture of the selected strain immediately resulted in very high chloroform depletion rates. Preliminary results of a study conducted with resting cells of the selected strain indicated that it can degrade chloroform concentrations up to 119 microM (14.2 mg l(-1)) without any sign of substrate toxicity, and that it is able to transform vinyl chloride and 1,1,2-trichloroethane.
Frascari
Dario
D
Department of Chemical and Mining Engineering and Environmental Technologies, University of Bologna, Via Terracini 34, 40131 Bologna, Italy. dario.frascari@guest.ing.unibo.it
Zannoni
Arianna
A
Fedi
Stefano
S
Pii
Youry
Y
Zannoni
Davide
D
Pinelli
Davide
D
Nocentini
Massimo
M
D000332:Aerobiosis; D001420:Bacteria, Aerobic / Q000302:isolation & purification / Q000378:metabolism*; D001711:Biotransformation; D002073:Butanes / Q000378:metabolism*; D002725:Chloroform / Q000378:metabolism*; D004785:Environmental Pollutants / Q000378:metabolism; D006843:Hydrocarbons, Chlorinated / Q000378:metabolism; D007700:Kinetics; D014240:Trichloroethanes / Q000378:metabolism; D014752:Vinyl Chloride / Q000378:metabolism
D002073:Butanes; D004785:Environmental Pollutants; D006843:Hydrocarbons, Chlorinated; D014240:Trichloroethanes; C024567:1,1,2-trichloroethane; C046888:butane; D002725:Chloroform; D014752:Vinyl Chloride