Improving the expression and secretion of GH48 family cellulases in C. acetobutylicum
Publication Date
July 12, 2018
Creator
Abstract
Although most energy is currently generated from fossil fuels, their continued use is unsustainable. Biofuels provide an attractive alternative. Unfortunately, such fuels are mainly produced from food crops, causing issues with food security. Lignocellulosic biomass represents the most logical alternative feedstock. However, its recalcitrance means that its use is currently limited by the economic costs involved in its deconstruction. One possible solution would be to undertake consolidated bioprocessing (CBP), a method by which cellulase production, cellulose degradation and fermentation take place in one step. To date, however, no suitable organism(s) have been identified.
Clostridium acetobutylicum is a promising candidate for the generation of a truly CBP organism as it can utilise all sugars present in lignocellulose and it has been used at an industrial scale to produce butanol. It is, however, not cellulolytic. Previous studies have shown that the main barrier to engineering C. acetobutylicum to grow on lignocellulose is the low level of production of cellulases from the GH9 and GH48 families. For this reason, the primary aim of this project was to increase the production of these particular cellulases.
To accomplish the project’s goal, several attempts were made to increase the level of expression of genes encoding GH48 family hydrolases in C. acetobutylicum. These cellulases were shown to be able to bind specifically to N-deacetylated but not acetylated peptidoglycan. C. acetobutylicum’s peptidoglycan was determined to be partially N-deacetylated. Proteins binding to peptidoglycan have been shown to be toxic to cells, which may explain the low level of secretion of GH48 family cellulases by C. acetobutylicum.
Item Type
ethesis
Thesis Type
PhD
Supervisors
Subjects (LC)
Associated Schools / Departments
School of Life Sciences
eprints ID
49716
UoN Repository URI
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Tom Wilding-Steele - Thesis Corrections final version 11.02.18.pdf
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