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Cometabolism of chlorinated solvents by nitrifying bacteria: Kinetics, substrate interactions, toxicity effects, and bacterial response
Author(s) -
Ely Roger L.,
Williamson Kenneth J.,
Hyman Michael R.,
Arp Daniel J.
Publication year - 1997
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/(sici)1097-0290(19970620)54:6<520::aid-bit3>3.0.co;2-l
Subject(s) - nitrosomonas europaea , chemistry , cometabolism , trichloroethylene , substrate (aquarium) , ammonia monooxygenase , methane monooxygenase , solvent , ammonia , non competitive inhibition , enzyme kinetics , enzyme , organic chemistry , chromatography , bacteria , nitrification , active site , bioremediation , biology , nitrogen , genetics , ecology
Pure cultures of ammonia‐oxidizing bacteria, Nitrosomonas europaea, were exposed to trichloroethylene (TCE), 1,1‐dichloroethylene (1,1‐DCE), chloroform (CF), 1,2‐dichloroethane (1,2‐DCA), or carbon tetrachloride (CT), in the presence of ammonia, in a quasi‐steady‐state bioreactor. Estimates of enzyme kinetics constants, solvent inactivation constants, and culture recovery constants were obtained by simultaneously fitting three model curves to experimental data using nonlinear optimization techniques and an enzyme kinetics model, referred to as the inhibition, inactivation, and recovery (IIR) model, that accounts for inhibition of ammonia oxidation by the solvent, enzyme inactivation by solvent product toxicity, and respondent synthesis of new enzyme (recovery). Results showed relative enzyme affinities for ammonia monooxygenase (AMO) of 1,1‐DCE ≈ TCE > CT > NH 3 > CF > 1,2‐DCA. Relative maximum specific substrate transformation rates were NH 3 > 1,2‐DCA > CF > TCE ≈ 1,1‐DCE > CT (=0). The TCE, CF, and 1,1‐DCE inactivated the cells, with 1,1‐DCE being about three times more potent than TCE or CF. Under the conditions of these experiments, inactivating injuries caused by TCE and 1,1‐DCE appeared limited primarily to the AMO enzyme, but injuries caused by CF appeared to be more generalized. The CT was not oxidized by N. europaea while 1,2‐DCA was oxidized quite readily and showed no inactivation effects. Recovery capabilities were demonstrated with all solvents except CF. A method for estimating protein yield, the relationship between the transformation capacity model and the IIR model, and a condition necessary for sustainable cometabolic treatment of inactivating substrates are presented. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 520–534, 1997.