Metabolic, Biokinetic and Bioenergetic Modelling of Microbial Environmental Bioprocesses

Abstract

The objective of this thesis is to build mechanistic models that utilize different approaches to solve different problems in biochemical engineering.

Firstly, a biokinetic mechanistic model is developed to describe the hydraulic, biological and physico-chemical processes occurring within a biotrickling filter used for the treatment of foul air from wastewater treatment facilities. The model presents an applicable general approach for describing reactor systems characterized by spatial and temporal concentration profiles and competition between biomass groups proliferating in separate niches. It was shown that there were multiple trade-offs in the choice of design and operating parameters, frequently between capital and operating costs to achieve the same desired level of pollutant removal. In addition, operating curves for given input parameters of gas flow rate and inlet H2S concentrations were generated.

Secondly, a methodology for detailed analysis of the bioenergetics of metabolic pathways was developed. The methodology in its simplest form is based on a clever transformation of the cell’s energy recovery objective into a linear optimisation problem for the network of biochemical reactions in study. The methodology is robust, generally applicable, highly scalable and offers the additional possibility of implementing more complex non-linear constrains as well as the optimisation of driving forces within the metabolic pathways of interest. The application and validity of the methodology is presented on the previously-studied and well-detailed propionate oxidation pathways and reverse TCA cycle pathway.

Lastly, the methodology presented earlier was applied to analyse the energetics of autotrophic CO2 fixation pathways at different environmental and biochemical conditions. The model produced helped understand the fundamental environmental and biochemical conditions that promote the growth of these valuable autotrophs by maximising their yield and uptake rate. In addition, a discussion on the possibility of deriving the choice of electron carriers from first principles was presented.

Overall, this thesis presents a unique view on the central divide between biokinetic models and bioenergetic models, and uses both approaches to further our comprehension of microbial bioprocesses.

Date of Award	Apr 2023
Original language	American English
Supervisor	Jorge Rodriguez (Supervisor)