Dissertation
PRODUCTION OF VOLATILE FATTY ACIDS FROM LIGNOCELLULOSIC BIOMASS MATERIAL: THE EFFECT OF BIOAUGMENTATION
Doctor of Philosophy (PhD), Washington State University
01/2018
Handle:
https://hdl.handle.net/2376/111815
Abstract
Volatile fatty acids (VFA), like acetic, propionic and butyric acids are currently produced by petrochemical sources and act as important platform molecules for the production of biofuels and biochemicals. Due to increasing energy demand and global warming, chemical industries are slowly shifting towards renewable substrates such as lignocellulosic biomass. Unlike pure cultures, mixed microbial cultures such as rumen, that have ability to degrade biomass, have the advantages of non-aseptic operation, flexibility of feedstock, stability of mixed cultures and minimal pretreatment of feedstock without the need for an expensive enzymatic hydrolysis. However, methanogen population in the rumen usually convert the VFAs to methane resulting in significant energy loss inside the anumal and eventually, adding to the global greenhouse gas emissions. The primary hypothesis of this study is to manipulate the rumen by inhibiting methanogenesis and redirecting in vitro fermentation towards efficient VFA production. Bioaugmentation is a process by which selected microbes are added to an existing microbial population to improve reactor performance and efficiency favorably. This process has never been successfully tested on rumen for this specific purpose.
In this, methanogenesis was selectively inhibited using sodium 2-bromoethanesulfonate and the reactors were bioaugmented with two strains of homoacetogens, on both corn stover and with a pure carbohydrate substrate, Avicel. After 99.5-99.7% methanogen inhibition, it was found that hydrogen accumulation in the headspace increased but there was a decrease in the VFA production. This decrease was due to negative effect of the increased H2 partial pressure on the cellulolytic population, studied using endoglucanase assay. However, bioaugmentation of this system shifted the rumen fermentation towards more acetic acid production, as seen by 80% increase in acetic acid production through almost 100% consumption of headspace hydrogen. Bioaugmentation also increased the endoglucanase activity by 78% and acetogenic activity of the rumen by 256-fold when compared to non-augmented reactors (after methanogenesi inhibition). The total VFA produced was reported in acetic acid equivalents. Hence, the results of this study confirm the hypothesis resulting in a higher VFA production (comparable to the current technology that predominantly use pure cultures) from biomass substrates using bioaugmented ruminal consortia.
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Details
- Title
- PRODUCTION OF VOLATILE FATTY ACIDS FROM LIGNOCELLULOSIC BIOMASS MATERIAL: THE EFFECT OF BIOAUGMENTATION
- Creators
- Nanditha Murali
- Contributors
- Birgitte K Ahring (Advisor)Stephen J Callister (Committee Member)Xiao Zhang (Committee Member)Hanwu Lei (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Voiland College of Engineering and Architecture
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 216
- Identifiers
- 99900581509501842
- Language
- English
- Resource Type
- Dissertation