Sustainable production of platform chemicals using novel synthetic biology and microbial fermentations

  • Laura Jeffrey

Student thesis: Doctoral Thesis

Abstract

Fluctuating oil prices and environmental concerns have led to a directed effort by industry to develop sustainable production of high value chemicals. Mesaconate, an industrially relevant platform chemical used in the production of methyl methacrylate, can be synthesised through the L-glutamate degradation pathway present in certain anaerobic organisms. This study investigates the potential of genes derived from this pathway to be expressed in Corynebacterium glutamicum, as a cellular factory to produce mesaconate in the first instance, with future scope to produce methyl methacrylate. C. glutamicum was chosen as a primary organism due to its existing industrial use as a microbial workhorse for the production of Lglutamate. Firstly, as the proposed process incorporated the initial over production of Lglutamate, various induction methods were investigated to establish an optimal process. Genetically engineered strains were then constructed and examined for their ability to produce mesaconate. Further process development was carried out to develop an efficient induction protocol. While the accumulation of mesaconate remains unclear, novel expression of the desired glutamate mutase and methylaspartate ammonia-lyase within C. glutamicum ATCC 13869 was established. A secondary approach where production of desired chemicals under oxygen limited conditions was examined. High cell densities of several mutant strains of C. glutamicum were investigated during a bioconversion process. Significant levels of succinic acid were achieved, however, further conversion to α-ketoglutarate, the precursor to L-glutamate was not observed. Co-factor regeneration appeared to be crucial for successful application of this process.Finally, toxicity of potential products and feedstocks were analysed to identify detrimental or toxic effects. While many of the compounds appeared to have little effect on the organisms examined, presence of methyl methacrylate, methacrylic acid and methanol significantly decreased growth and/or production. Design of future processes will be significant in maintaining these compounds at non-inhibitory levels to ensure efficiency.
Date of Award1 Oct 2015
LanguageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsUniversity of Strathclyde & University of Dundee
SupervisorBrian McNeil (Supervisor) & (Supervisor)

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