Dissertation
ENZYMATIC SYSTEMS IN BIOLOGICAL LIGNOCELLULOSE DEGRADERS AND THEIR ROLE IN LIGNIN MODIFICATION
Doctor of Philosophy (PhD), Washington State University
01/2017
Handle:
https://hdl.handle.net/2376/117746
Abstract
A key step in developing biofuel is pretreatment, as this step remains the bottleneck in designing an efficient and economical technology for producing biofuels from lignocellulosic biomass. Although various pretreatment methods are available for deconstructing lignocellulosic biomass and obtain cellulosic sugars, they have several disadvantages, including high energy requirements and chemical input. Biological pretreatment of biomass using fungi and bacteria has been long studied to overcome the challenges related to thermochemical pretreatment. The dissertation research focuses on the mechanism elucidation and understanding of these systems to make it possible to develop a pretreatment process that could mimic them. This project aimed to elucidate these biological systems from an enzymatic perspective. The project involved a series of three studies.
In the first study, the pretreatment of lignocellulosic biomass, wheat straw, by a white-rot fungus was examined. The extracellular proteome of this fungus was investigated and the pretreated biomass was characterized. This allowed the development of a schematic mechanism to explain the strategy of synergism between the ligninolytic enzymes to pretreat the biomass.
In the second study, a more evolved and complex organism, the Formosan termite, as a system was used to examine the lignin deconstruction mechanism. The midgut proteome of this system was examined to explore the enzymes that can modify lignin in the biomass. Based on the enzymes identified, a speculative schematic was proposed to explain the specific modifications of the -O-4 lignin bond in the termite gut.
In the third and final study, a putative superoxide dismutase in the termite midgut was confirmed through expression studies in bacteria and yeast hosts. The expressed enzyme was purified to determine the enzyme activity. This enzyme was proposed as a ‘novel ligninase’, based on its role in lignin modification with the help of Reactive Oxygen Species (ROS).
The findings from these studies will contribute to the design of in-vitro pretreatment methods inspired from biological degraders of biomass. The results also provide insight for further research on the termite proteome as well as characterization of unknown enzymes.
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Details
- Title
- ENZYMATIC SYSTEMS IN BIOLOGICAL LIGNOCELLULOSE DEGRADERS AND THEIR ROLE IN LIGNIN MODIFICATION
- Creators
- Innu Chaudhary
- Contributors
- Shulin Chen (Advisor)Wei-Jun Qian (Committee Member)Jianzhong Sun (Committee Member)David R Gang (Committee Member)Bin Yang (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Biological Systems Engineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 158
- Identifiers
- 99900581718801842
- Language
- English
- Resource Type
- Dissertation