الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The present thesis had been focused on developing an efficient bioprocess and microbial platform for biofuel and chemicals production through fermentation of environmental pollutants using acetogenic bacteria. Different inoculum (mesophilic and thermophilic) were used through the biogas upgrading and volatile fatty acids production process. First, series of experiments were performed to identify the best pre-treatment (chemical and thermal) method that inactivates the methanogenic archaea in the inocula and enriches the acetogenic bacteria. Subsequently, the optimum H2: CO2 gas ratio for maximum biogas upgrading efficiency and production of chemicals was assessed. In addition, 16S rRNA analysis of the microbial community was conducted to better understand the process from the microbiological point of view. Another study was also performed to identify optimal conditions for high efficient ethanol and volatile fatty acids (VFAs) production from synthetic gas fermentation.
The thermal treatment of the mesophilic inoculum at (70 or 90°C for 30 min) did not inhibit methanogenesis at all, while the chemical (BES) treatment had completely blocked the activity of methanogenic archaea and enhanced the VFAs production. Therefore the present study was successed in converting CO2 in the biogas and the externally added H2 to valuable chemicals (e.g., volatile fatty acids) and contributed efficiently in biogas upgrading.
The biogas was upgraded using chemically treated mesophilic inoculum to biomethane (methane content 96%) which can be used as vehicle fuel or injected into the natural gas grid, while the thermophilic inoculum achieved a lower concentration of biomethane (77%). homoacetogenic pathway in the chemically treated inoculum was mainly mediated by A. noterae 10 (a hydrogen scavenger), while Moorella sp. was the dominant acetogen through the thermophilic fermentation.
Acetate was the most dominant product independent of inoculum type through the study focused on identifying the optimal conditions for high efficient ethanol and volatile fatty acids (VFAs) production from synthetic gas fermentation. C. ragsdalei had shown higher ability on ethanol production through CO fermentation compared to mixed culture fermentation.