碩士 / 國立中興大學 / 環境工程學系所 / 100 / Microalgae are considered as a promising feedstock for biodiesel production to mitigate the world energy crisis and global warming because of their high growth rate, low carbon dioxide emission, and low competition to agricultural crops. In addition, some studies also indicated that microalgae can remove nutrients from wastewater. In this study, the effect of cultivation conditions (CO2 concentration, light intensity, nitrogen-limiting strategy, ammonia concentration, ammonia-N/nitrate-N ratio, and different culture mediums) on microalgae growth and lipid accumulation was investigated. Besides, a wastewater was used to evaluate the feasibility of the combination between biodiesel production and wastewater nutrient removal.
Among all isolated strains, Monoraphidium sp. showed the highest lipid content (26.2%) and was able to grow in the medium that simultaneously contained nitrate and ammonia. Considering the aim of wastewater nutrient removal, this microalgae strain was selected for further investigation.The cultivation result showed that the growth rate of Monoraphidium sp. increased from 0.399 day-1 to 1.613 day-1 when CO2 concentration increased from 0.03% to 3%. However, the growth rate did not increase even higher when the CO2 concentration elevated to 8% or 15%, In addition, the lipid contents had no significant difference within various CO2 concentrations. On the other hand, the growth and lipid contents were almost the same under the light intensities of 200 mE/m2s and 400 mE/m2s, which may be attributed to light saturation for Monoraphidium sp.. Therefore, the biomass production and lipid accumulation were invariable even though the light intensity increased. In this study, two types of nitrogen limiting strategies were conducted to induce the lipid accumulation of Monoraphidium sp.. From the results of our experiments, neither single-stage nor two-stage cultivation enhanced the lipid content. These results revealed that the nitrogen limitation may not be a stress for Monoraphidium sp. to enhance lipid accumulation. Since ammonia was the sole nitrogen source in the experiment, Monoraphidium sp. was not well grown in the medium and started to decay. However, the cell growth and ammonia assimilation of Monoraphidium sp. were stimulated when the medium was infused with little amount of nitrate. When the nitrate concentration was 2.8 mg/L, Monoraphidium sp. can survive under an ammonia concentration of up to 560 mg/L. Finally, a wastewater was used to incubate Monoraphidium sp. and the strain can utilize nutrients from wastewater to grow with lipid accumulation. Moreover, the major fatty acids of lipid composition were 16:0 and 18:1, which are suitable for biodiesel manufacturing. According to the results from this study, Monoraphidium sp. should be an ideal candidate for simultaneous biodiesel production and wastewater nutrient removal.
| Identifer | oai:union.ndltd.org:TW/100NCHU5087035 |
| Date | January 2012 |
| Creators | Jia-Wen Chen, 陳佳雯 |
| Contributors | Chi-Mei Lee, 李季眉 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 85 |
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