| Summary: | 碩士 === 國立交通大學 === 分子醫學與生物工程研究所 === 102 === Anaerobic digestion of microalgae will be a potential component of microalgae biofuel production system. In this study, a batch anaerobic digestion was conducted to evaluate the effects of lipid extraction (LE) and thermal-chemical hydrolysis (TCH) for enhancing methane yield from microalgae. The results exhibited that lipid extraction could reduce the HRT (Hydraulic Retention Time) of anaerobic digestion and promote the potential of TCH. The optimum condition of TCH was carried out at 0.5 % (w/w) sulfuric acid and 120 ℃ temperatures. Thermal-chemical hydrolysis increased biodegradability of microalgae and LE residue from 11 % to 19 % and 9 % to 46 %, respectively. When digestion of microalgae was S/I ratio = 1, TCH and the LE process increased methane yield, up to 52 % and 10 % respectively. The combination effect increased yield by 102 % over that of the raw microalgae (93.5 ± 6.0 mL CH4 / g CODadd). In addition, we replaced a part of microalgae with crude glycerol to adjust the C/N Ratio of feeding. However, co-digestion with crude glycerol and microalgae increased 42 % of methane production at a C/N Ratio of 5.24. After pretreatments and co-digestion of microalgae, the conversion rate of COD to methane increased from 27 % to 77 %. Then, microbial community shifts were determined by denaturing gradient gel electrophoresis (DGGE). Microbial community structures showed continuous shifts within five bacterial phyla and three archaea. Bacteroidetes-like and Firmicutes-like organisms, appeared to be responsible for degradation of microalgae. Syntrophus-like and Smithella-like organisms involved acidogenesis or syntrophic acid degradation. And, Deltaproteobacteria- like organisms produced hydrogen sulfide (H2S) in biogas. Both hydrogenotrophic and aceticlastic methanogens appear to have been involved in the methanogenesis with the acidogenic products, such as Methanosaeta and Methanosarcinales.
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