Microbial co-existence and stable equilibria in a mechanistic model of enteric methane production : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Mathematics at Massey University, Manawatū Campus, New Zealand
Loading...
Date
2016
DOI
Open Access Location
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Massey University
Rights
The Author
Abstract
Globally, 14.5% of all anthropogenic greenhouse gases come from ruminants.
One of these is methane, which is produced in the rumen of
ruminant animals. Feed is degraded by microbes to produce volatile fatty
acids (which are absorbed by the animal) and hydrogen (which is metabolized
by methanogens to form methane). The dynamics of hydrogen production
and metabolism are subject to thermodynamic control imposed
by the hydrogen concentration. Existing models to estimate methane
production are based on calculation of hydrogen balances without considering
the presence of methanogens and do not include thermodynamic
control. In this project, a model is developed based on glucose-hydrogenmethanogen
dynamics to estimate methane production and illustrates a
co-existence of microbes that employs different fermentation pathways
competing for the same food source in the rumen. Glucose was chosen
as an example of a fermentable feed component. A thermodynamic
term was integrated into a Monod-type model to represent the thermodynamic
control of hydrogen concentration on the rates of hydrogen
generation and hydrogen metabolism. Results of this model suggest that
the microbial community composition and the combination of the different
pathways are determined by the rumen environment, biological
parameters of the microbes and the feedback imposed by substrate and
product concentrations. The mathematical enunciation of this model is
therefore consistent with biological expectations. This model could be
expanded to include plant polymer degradation rate, feeding level and
feeding frequency to explore their effects on methane production. This
model could also be integrated into models of whole rumen function to
address more complex questions. It would also support experimentation
with animals for understanding factors that control methane formation
and to explore methane mitigation strategies.
Description
Keywords
Methane, Hydrogen metabolism, Mathematical models, Methanobacteriaceae, Rumen, Microbiology, Research Subject Categories::MATHEMATICS::Applied mathematics