Influence of mass transfer limitations on determination of the half saturation constant for hydrogen uptake in a mixed‐culture CH₄‐producing enrichment

Abstract

There is strong evidence in the literature supporting the existence of significant mass transfer limitations on the kinetics of exogenous H(2) consumption by methanogens. The half saturation constant for H (2) uptake by a mixed-culture, CH(4) producing enrichment was measured using an experimental protocol that avoided internal mass transfer limitations. The value obtained was two orders of magnitude smaller than any other previously reported. A mathematical model for acetogenic syntrophic associations was developed to check the capacity of H(2) as electron transporter between syntrophic partners. It was found that H(2) diffusion could account for the rate of transport of electrons between the syntrophic microorganisms and that formate is not a necessary intermediate. The possibility that formate may be an intermediate in this system was not ruled out. A Monod-type kinetic equation was modified to include the observed H(2) threshold effect. This modified equation was used to predict the CH(4)-production rate in a batch-fed digester. The results show that the external and internal H(2) pools are kinetically coupled.

A practical kinetic model that considers endproduct inhibition in anaerobic digestion processes by including the equilibrium constant

“…Thus, substrate threshold values appear to be a new and important parameter that may significantly influence anaerobic reactions such as hydrogen oxidation. The use of the H2 threshold value in kinetic models has also been proposed recently (Giraldo-Gomez et al, 1992). When the concentration of the substrates is far higher than that of the products and the reaction driving force is large, the ratio T/K becomes very small and the model predictions approach those of the classical Michaelis-Menten model (see also Figs.…”

“…These threshold values indicated that bacterial reaction kinetics do not necessarily result in the complete utilization of the substrate. The existence of hydrogen threshold values indicated that v,,, values and k , values alone may not be sufficient to predict the efficiency of utilization of low hydrogen concentrations (Giraldo-Gomez et al, 1992;Lovley, 1985). These hydrogen threshold values were found to be related to the free energy change of the reaction (Cord-Ruwisch et al, 1988).…”

“…Reaction conditions: HCOj (50 mM); acetate-(10 mM); SO,'-(10 mM); HS-(10 mM); CH2 (50 kPa); pH 7; 25°C. k,,,,, and v,,, values are assumed to be identical for all runs (1 mM and 2 mM/ h, respectively) "leftover" substrate has been established for bacterial hydrogen degradation in natural environments (Cord-Ruwisch et al, 1988;Giraldo-Gomez et al, 1992;Michaelis and Menten, 1913). Hydrogen is a major intermediate compound in the anaerobic degradation of organic matter.…”

Ecological control analysis: being(s) in control of mass flux and metabolite concentrations in anaerobic degradation processes

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Modeling and analysis of layered stationary anaerobic granular biofilms

“…The biological part of the model is described by the biomass production dependencies. In the literature (e.g., Angelidaki et al, 1993;Buffiere et al, 1995;Giraldo-Gomez et al, 1992) there is evidence to suggest that Monod-type kinetics would be sufficient to portray acidogenic growth on glucose, growth of the syntrophic association on hydrogen, and methanogenic growth on acetate,…”