On 20 November at 14:15 Scott Bottoms will defend his thesis “Engineering Robust Microbial Systems and Biocatalysts for Improved Lignocellulosic Feedstock Conversion” for obtaining the degree of Doctor of Philosophy (Molecular Biotechnology)
Supervisior:
Professor Tanel Tenson, University of Tartu
Opponent: Senior Researcher Oskars Grīgs
Latvian State Institute of wood chemistry, Latvia
Summary: Biological conversion of lignocellulosic biomass provides a route to renewable fuels and chemicals, but its performance depends on feedstock composition, processing conditions, and the microorganisms and enzymes used. This thesis examines these limitations through four studies combining chemical genomics, microbial strain engineering, and experimental enzyme characterization.
The first study showed that drought-related changes in switchgrass composition affected pretreatment chemistry and inhibited subsequent yeast fermentation. This finding connects environmental conditions during biomass production with downstream conversion performance. Two further studies investigated the toxicity of imidazolium ionic liquids and gamma-valerolactone, which can remain after biomass processing. Their effects were associated with mitochondrial dysfunction and increased cell membrane permeability, respectively. Genetic changes identified through chemical genomics improved yeast tolerance, sugar utilization, and ethanol production under the corresponding inhibitory conditions.
The fourth study evaluated ancestral sequence reconstruction as an approach to enzyme engineering. Experimental characterization confirmed that selected reconstructed enzymes retained activity and revealed differences in thermal stability, showing that reconstructed sequences can yield functional biocatalysts.
Together, these studies connect feedstock variability and processing chemistry with microbial performance and demonstrate approaches to engineering tolerant microorganisms and evaluating functional biocatalysts. The work provides experimental evidence to guide the development of biological systems for lignocellulosic feedstock conversion.
Defence can be followed in Zoom: Doctoral Defence (meeting ID: 953 058 8152, passcode: kaitsmine)
