A Procedure to Determine the Uncertainties in Kinetic Parameters Obtained by Extant Respirometry

Kinetic parameters obtained experimentally should be reported as mean values with confidence intervals that incorporate the uncertainties encountered in fitting experimental data to a nonlinear model. A source of uncertainty unique to respirometry is the separation of the experimental oxygen consumption rate data into endogenous and exogenous components. A portion of the data is used to estimate the endogenous rate that is then subtracted from the measured oxygen consumption rate to “normalize” the data before the kinetic parameters are estimated by fitting the model to the exogenous oxygen consumption. This paper proposes a procedure to incorporate the uncertainties of respirometric data normalization with the other uncertainties to define a two dimensional confidence region for Monod model parameters including an approach to express the confidence region in a simple numerical form. Using this approach we demonstrate that normalization using post-exogenous (rather than pre-exogenous) data minimizes uncertainty in the Ks estimate.