Biokinetic models for representing the complete inhibition of microbial activity at high substrate concentrations

Abstract

This paper reintroduces the Wayman and Tseng model for representing substrate inhibition effects on specific growth rate by further documenting its potential predictive capabilities. It also introduces a modification to this model in which an Andrews inhibition function is used in place of the Monod noninhibitory substrate function. This modification better represents the relationship between specific growth rate and substrate concentration for those substrates that show Andrews type inhibition at lower substrate concentrations, rather than the Monod type noninhibitory behavior described in the model of Wayman and Tseng. Results from nonlinear, least squares regression analysis are used to evaluate the ability of these models to empirically represent experimental data (both new and from the literature). The statistical goodness of fit is evaluated by comparing the regression results against those obtained using other empirical models. Finally, possible mechanisms of toxicity responsible for the observed inhibition trends are used to further justify use of these empirical models. The dominant mechanism considered to be relevant for conceptually explaining complete inhibition at high concentrations of solvents is the deterioration of cell membrane integrity. Literature citations are used to support this argument. This work should lead to improvements in the mathematical modeling of contaminant fate and transport in the environment and in the simulation of microbial growth and organic compound biodegradation in engineered systems.

Substrate inhibition kinetics for toluene and benzene degrading pure cultures and a method for collection and analysis of respirometric data for strongly inhibited cultures

“…The Wayman and Tseng equation cannot model this behavior. The modified Wayman and Tseng equation, introduced by Alagappan and Cowan (2001) with the Andrews function in place of the Monod function (Table I), worked well to describe this data (Table V). The magnitude of the inhibition coefficient, i, in both the Wayman and Tseng model and its proposed modification can be looked at as a measure of the degree of toxicity experienced by the organisms.…”

“…The Luong model regression results were selected for use in Table V in place of the slightly statistically superior Wayman and Tseng model regression results because the statistical benefit was small compared to the perceived cost of changing from a continuous to a dis-continuous model. As explained in Alagappan and Cowan (2001) for data showing the observed trend seen for these conditions the Luong model is generally preferred. It is only when there is an extended region of near constant maximum specific growth rate over a substantial range of substrate concentrations that the cost of using the discontinuous Wayman and Tseng model is necessary.…”

Empirical model representing microbial activity in a submerged MBR treating strength wastewater

“…dt (1) where OUR is oxygen uptake rate, d[O2] is the change in dissolved oxygen concentration in reactor and dt is the change of time. DO was measured in the reactor and the OUR was monitored automatically by switching off the aeration and measuring the decrease in DO from 6 to 4 mgO2/1.…”

“…The use of sophisticated models to simulate compound fate and transport in natural and engineered systems has seen rapid growth since the introduction of inexpensive computers in the early 1980s [1]. In the field of environmental engineering, the submerged membrane bioreactor (sMBR) has recently been graining much attention for wastewater treatment in aspects of better effluent quality and lower sludge production compared to the conventional activated sludge *Corresponding author.…”

Toluene inhibition on an anaerobic reactor sludge in terms of potential activity and composition of acetoclastic methanogens

“…[5][6][7][8][9] Downloaded by [University of Hawaii at Manoa] at 15: 24 27 December 2014 In this study, it is therefore aimed to determine the effect of toluene on an anaerobic sludge taken from a fullscale upflow anaerobic sludge blanket (UASB) reactor in terms of potential activity and composition of acetoclastic methanogens. The SMA tests had been carried out to determine the effect of different toluene concentrations on the potential acetoclastic methanogenic activity of the anaerobic sludge.…”