Engineering Parageobacillus thermoglucosidans as a robust platform for bioethanol production
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Date
2018
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University of the Western Cape
Abstract
Parageobacillus thermoglucosidans is a promising “platform” organism to use in the production ofa
range of useful metabolites with demonstrated ability to produce ethanol, isobutanol and polylactic acid
for bio-degradable plastics. Extensive work has been done in engineering the organism for enhanced
ethanol production. However, an often used and highly effective alternative pathway (pyruvate
decarboxylase mediated) for ethanol production has not yet been demonstrated in P.
thermoglucosidans. We first characterize two novel bacterial pyruvate decarboxylase enzymes
(PDC’s) then attempt to express the more thermostable of these enzymes from Gluconobacter oxydans
in P. thermoglucosidans to improve ethanol yields. Initial expression was unsuccessful. Analysis of
the codon usage pattern for the gene revealed that the codon usage was suboptimal in the heterologous
host P. thermoglucosidans. After codon harmonization, we could demonstrate successful expression
of the enzyme at 45°C, however not at the bacterium’s optimum growth temperature of 60°C. This was
concomitant with enhanced ethanol production close to the theoretical yield possible (0.5g/l).
Description
Philosophiae Doctor - PhD (Biotechnology)