Dissertation
SYSTEMATIC LABORATORY EVALUATIONS OF HYPERTHERMOPHILIC ANAEROBIC DIGESTION OF DAIRY MANURE AND CORN STOVER WITH THE EMPHASES ON HYDROLYSIS AND ACIDIFICATION
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2022
DOI:
https://doi.org/10.7273/000004359
Handle:
https://hdl.handle.net/2376/118922
Abstract
Anaerobic digestion (AD) is widely considered as a promising technology to treat diverse biowastes for renewable energy production. Due to the limited hydrolysis of recalcitrant lignocelluloses under conventional conditions, hyperthermophilic anaerobic digestion (HTAD) has attracted great attention by virtue of promoted solubilization. However, fundamental studies about the degradation rate of different organic matters and volatile fatty acids (VFAs) constitution during HTAD process are still lacking. The rationale for the improved hydrolysis under hyperthermophilic temperatures governed by pivotal hydrolytic enzymes and responsible microbiome requires in-depth investigation. Therefore, this work aims to explore the lignocellulosic conversion in HTAD, with emphases on hydrolysis and acidogenesis of dairy manure (DM) and methanogenesis of corn stover (CS). The work also includes the specific discussion of the microbial community, hydrolytic enzymes, and metabolic pathways affected by elevated temperature.
To identify the current gaps in HTAD, a comprehensive review was first conducted, including lignocellulose degradation, VFAs production, biogas productivity, the shift of both microbial community and metabolic pathways during HTAD process.
Next, hydrolysis and acidogenesis of DM were investigated under hyperthermophilic temperatures versus mesophilic and thermophilic temperatures. Results showed that HTAD enhanced the degradation of crude protein and hemicellulose as the increased population of xylanolytic Caldicoprobacter and proteolytic Thermovirga. It further contributed to the improved VFAs production rate at an early stage.
The following study explored the enzymatic activities of pivotal hydrolase and predicted those enzyme genomes in microbiome. All types of hyperthermophilic enzymes, especially proteases, exoglucanases, and β-glucosidases displayed higher activities compared to conventional AD during DM hydrolysis. Caldicoprobacter was the main contributor carrying more hydrolytic enzymes per genome including endoglucanase, β-glucosidase, and xylanase in HTAD.
The final study examined the effects of HTAD on methane yield and content from CS. Although mesophilic AD is considered preferable for methane production, results showed that acclimated hyperthermophilic inoculum can simultaneously produce high content methane and efficiently degrade CS for VFAs production.
This work highlighted HTAD advantages for treating lignocelluloses compared to traditional AD in terms of hydrolysis, acidogenesis, and methanogenesis. The HTAD technology holds promise in processing lignocelluloses for VFAs production, biogas production, and biowaste utilization.
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Details
- Title
- SYSTEMATIC LABORATORY EVALUATIONS OF HYPERTHERMOPHILIC ANAEROBIC DIGESTION OF DAIRY MANURE AND CORN STOVER WITH THE EMPHASES ON HYDROLYSIS AND ACIDIFICATION
- Creators
- Yaojing Qiu
- Contributors
- Shulin Chen (Advisor)Juming Tang (Committee Member)John Peters (Committee Member)Yiyong Liu (Committee Member)Xiujin Li (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Biological Systems Engineering, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 231
- Identifiers
- 99900883035901842
- Language
- English
- Resource Type
- Dissertation