A COMETABOLIC KINETICS MODEL INCORPORATING ENZYME-INHIBITION, INACTIVATION, AND RECOVERY .1. MODEL DEVELOPMENT, ANALYSIS, AND TESTING

Cometabolic biodegradation processes are important for bioremediation of hazardous waste sites. However, these processes are not well unders tood and have not been modeled thoroughly. Traditional Michaelis-Mente n kinetics models often are used, but toxic effects and bacterial resp onses to toxicity may cause changes in enzyme levels, rendering such m odels inappropriate. In this article, a conceptual and mathematical mo del of cometabolic enzyme kinetics is described. Model derivation is b ased on enzyme/growth-substrate/nongrowth-substrate interactions and i ncorporates enzyme inhibition (caused by the presence of a cometabolic compound), inactivation (resulting from toxicity of a cometabolic pro duct), and recovery (associated with bacterial synthesis of new enzyme in response to inactivation). The mathematical model consists of a sy stem of two, nonlinear ordinary differential equations that can be sol ved implicitly using numerical methods, providing estimates of model p arameters. Model analysis shows that growth substrate and nongrowth su bstrate oxidation rates are related by a dimensionless constant. Relia bility of the model solution procedure is verified by analyzing data s ets, containing random error, from simulated experiments with trichlor oethylene (TCE) degradation by ammonia-oxidizing bacteria under variou s conditions. Estimation of the recovery rate constant is determined t o be sensitive to initial TCE concentration. Model assumptions are eva luated in a companion article using data from TCE degradation experime nts with ammonia-oxidizing bacteria. (C) 1995 John Wiley & Sons, Inc.