Thesis
Engineering Streptomyces clavuligerus for efficient growth on sustainable carbon sources
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2020
- Thesis identifier
- T15841
- Person Identifier (Local)
- 201680038
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Streptomyces clavuligerus is the industrial producer of the β-lactamase inhibitor, clavulanic acid (CA). This compound is one of the components of the co-formulation generically known as co-amoxiclav. This pharmaceutical combines CA and amoxycillin and is industrially produced by GlaxoSmithKline (GSK), which markets the drug under the trade name Augmentin. The industrial-scale fermentation with S. clavuligerus, the process by which CA is produced by GSK, requires human food-grade and costly carbon sources as feedstocks. To make the industrial production of CA more sustainable and economical, GSK would like to source industrial by-products as feedstocks. Yet, S. clavuligerus has a limited carbon catabolic profile, its preferred carbon source being glycerol, which does not allow the use of alternative sources of carbon, such as glucose. S. clavuligerus was considered naturally glucose auxotrophic due to the lack of a glucose uptake system. In streptomycetes, glucose is transported into the cell via a glucose permease (GlcP) and subsequently phosphorylated by a glucokinase (Glk). Although genes encoding GlcP and Glk, glcP and glk, respectively, are present on the S. clavuligerus genome, expression of the former is too low to enable sufficient uptake of the hexose to support growth. Industrial production strain improvement traditionally involved random mutagenesis and subsequent rounds of selection of strains exhibiting desirable traits, such as improved antibiotic titres. Yet, with this approach, altered phenotypes cannot be linked to changes in genotypes. Therefore, the focus of this thesis was to gain an understanding of carbon utilisation of two industrial strains provided by GSK: SC2 and SC6. Subsequently, a targeted approach to improving glucose utilisation was taken by expressing streptomycete glcP and glk genes. This showed that, contrary to previous reports on CCR in a wildtype background, glucose triggers repression of CA biosynthesis in the earlier production strain. Furthermore, the strains were found to be de-regulated in their production of extracellular proteases, which might affect nutrient uptake and utilisation during fermentation. Protein-protein interaction between GlcP and Glk from S. clavuligerus, further, revealed a lack of interaction. GlcP and Glk are known to interact in S. coelicolor, a glucose utilising streptomycete. Overall, this thesis provides findings of aspects of the central carbon metabolism of an industrially relevant organism. Further, advantages of rational strain improvement are highlighted by heterologous expression of genes of interest and being able to directly link observed phenotypes.
- Advisor / supervisor
- Hunter, Iain
- Hoskisson, Paul
- Resource Type
- Note
- This thesis was previously held under moratorium from 30/03/2021 to 03/04/2024
- DOI
- Date Created
- 2020
- Former identifier
- 9912980590302996
- Funder
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