Characterisation of the native β-alanine pathway in Cupriavidus necator H16: an attractive route towards 3-hydroxypropionic acid production.

Orol Gómez, Diego (2020) Characterisation of the native β-alanine pathway in Cupriavidus necator H16: an attractive route towards 3-hydroxypropionic acid production. PhD thesis, University of Nottingham.

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Abstract

The sustainable production of chemicals and fuels through microbial fermentation will play a pivotal role in reducing our dependence on fossil resources as well as decreasing global emissions of greenhouse gases, and in particular CO2. A particularly promising strategy is to produce the requisite molecules using autotrophic microbial chassis that are capable of growing on CO2 as a sole carbon source. One such chassis is Cupriavidus necator H16, formerly Rastonia eutropha. It is a Gram-negative, non-pathogenic, asporogenous bacterium found in aerobic and anaerobic, non-halophilic environments. It is a facultative, chemolithoautotroph able to grow aerobically on CO2 and H2 as sole carbon and energy source, respectively. It can also grow heterotrophically on a variety of organic substrates.



3-Hydroxypropionic acid (3-HP) is one of these potential chemicals. It is a platform chemical, which can be converted into a wide variety of acids and biodegradable polyesters, among other highly valued industrial compounds. Currently, industrial demand for 3-HP is entirely met through petrochemical routes which are associated with environmental pollution. A biological process involving genetically engineered microorganisms would potentially be a sustainable manner of production that industry will surely support and value.

Metabolic modelling has previously identified a number of potential routes to 3-HP of which a process that proceeds via β-alanine (BAL) represents the most energy efficient pathway. Whilst C. necator possesses a putative native BAL pathway, it does not presently produce 3-HP.

The current study sought to investigate the potential of the native BAL metabolic route in C. necator for the production of 3-HP, focusing our efforts on the phenotypical and enzymatic characterisation of the last two metabolic steps of the pathway, from the pyruvate-dependent transamination reaction between BAL and malonate semialdehyde (MSA) to the reduction of MSA to 3-HP. This analysis demonstrated that a putative transaminase (CnAptA) and two putative dehydrogenases (CnHpdH and CnHbdH) were largely responsible for the failure of C. necator to produce 3-HP.

Following strain development, a heterologous pathway was implemented in the organism which led to the total conversion of BAL into 3-HP. This innovation could form the basis of the future production of sustainable and commercially viable amounts of 3-HP using CO2 as the sole carbon source in C. necator H16.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Kovacs, Katalin
Minton, Nigel
Keywords: Cupriavidus necator H16, 3-hydroxypropionic acid, β-alanine, CO2
Subjects: Q Science > QR Microbiology > QR 75 Bacteria. Cyanobacteria
Faculties/Schools: UK Campuses > Faculty of Medicine and Health Sciences > School of Life Sciences
Item ID: 60481
Depositing User: OROL GOMEZ, Diego
Date Deposited: 31 Jul 2020 04:40
Last Modified: 14 Aug 2020 09:22
URI: http://eprints.nottingham.ac.uk/id/eprint/60481

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