Lignin is a complex, highly aromatic and heterogenous plant polymer present in lignocellulosic biomass, and is second only to cellulose as the most abundant biopolymer on earth, representing the largest naturally occuring renewable source of aromatics. However, the remarkable recalcitrance of lignin to economically feasible (bio)degradation, with the exception of a handful of microbial species, has meant that the latent potential of this biopolymer for applied uses has largely remained untapped. The natural degradation of lignin contained in lignocellulosic biomass is carried out almost exclusively by a sub-kingdom of fungi, known as basidiomycetes (white-rot fungi), which secrete different enzymes acting both separately, and in synergy, to degrade lignin signifcantly enough for these organisms to mineralize it to CO2 and thus gain access to the plants energy rich cellulose. Though these enzymes are known to degrade lignin when secreted by fungi and when applied in vitro, what is not known is whether they can be expressed in vivo by the lignocellulosic plant itself for auto-lignin degradation, a novel strategy which would circumvent the need for whole fungi or standalone enzyme treatment to biologically degrade lignin. The benefits of a such a novel auto-pretreatment strategy in lignocellulosic plants would fill a pressing need for cost effective lignin degradation in the production of renewable chemicals and biofuels. Lignin plays vital roles in living plants, making it detrimental to reduce lignin content constitutively. Therefore it would be much more feasible to reduce lignin just before harvest of the biomass in a controlled manner. The main focus of the research presented in this thesis is the development and validation of transgenic approaches to chemically induce the overexpression of lignin degradation enzymes in planta within the model organism Arabidopsis thaliana and deliver them to the cell wall for controlled lignin degradation in a proof-of-concept study.
|Date of Award||Dec 2020|
- Queen's University Belfast
|Sponsors||Northern Ireland Department for the Economy|
|Supervisor||Fuquan Liu (Supervisor), Christopher C R Allen (Supervisor) & Meilan Huang (Supervisor)|
- plant cell wall
- Manganese peroxidase
- Trametes versicolor