博士 / 國立中興大學 / 環境工程學系所 / 103 / Microalgal lipids are regarded as potential sustainable biodiesel feedstocks in the future, because microalgae have a much higher growth rate and photosynthetic efficiencies in comparison with conventional crops. Microalgae can adapt to lots of different area including extreme environment and utilize nutrients from wastewater. If microalgae are cultivated in wastewater, they can remove nutrients from the wastewater and produce oil at the same time. The apparent benefits of combining microalgal biodiesel production and wastewater treatment are the methods to minimize the use of freshwater, reduce the cost of nutrient addition for microalgal cultivation, and remove nitrogen and phosphorus from effluents. Depending on species and culture conditions, such as temperature, illumination, nutrients, and carbon source, microalgal oil content and composition are varied.
In this study, we screened lipid accumulation potential of microalgae from local microalgal strains in Taiwan, evaluated the optimal culture conditions in artificial medium. Besides, the possibility of microalgae cultivated in industrial park wastewaters for cell growth as well as lipid accumuluation by microalgae were estimated.
Seven microalgal strains were test in this study. Ammonium or nitrate was completely assimilated by Chlorella sp. IWB-1 in the culture medium. Among that, most strains could grow well between pH 5~10. The growth rate of Chlorella sp. CEM-2 was reduced at pH 5, and the growth of Chlorella sp. IWB-1 was not influenced until pH value was under pH 3. Monoraphidium sp. SB2 was selected to test the other optimal culture conditions because of its higher lipid content compared to other strains, either cultured in industrial park wastewater or artificial medium.
Monoraphidium sp. SB2 could grow well between 25~35oC incubation temperature and it has higher lipid productivity at 30oC. Monoraphidium sp. SB2 showed higher biomass and lipid productivity under continuous illumination. Lipid content of Monoraphidium sp. SB2 was not influenced with different nitrogen sources. Monoraphidium sp. SB2 showed highest lipid productivity when ammonianitrate was the nitrogen sources. The dominant compositions of fatty acids in this microalgal lipid were saturated fatty acid:palmitic acid (C16:0) and unsaturated fatty acid:oleic acid (C18:1), linoleic acid (C18:2), and linolenic acid (C18:3).
Monoraphidium sp. SB2 showed obviously higher lipid content under the condition of nitrogen deficient than that under nitrogen sufficient. Lowest lipid content was obtained in this microalgal strain at logarithmic growth phase but significant lipid accumulation at stationary phase under nitrogen deficient.
The addition of carbon sources seemed to siginificantly improve biomass production but to negatively impact on lipid content for Monoraphidium sp. SB2. Under 3% CO2 aeration, the biomass production of Monoraphidium sp. SB2 was increased with the nitrogen concentrations of 100 mg N/L and 150 mg N/L. The addition of sucrose was also increased microalgal biomass. Monoraphidium sp. SB2 showed highest lipid content under air aeration and lowest lipid content with sucrose as carbon sources. Monoraphidium sp. SB2 showed highest lipid productivity (161 mg/L/d) under 3% CO2 aeration and with the nitrogen concentrations of 150 mg N/L.
When Monoraphidium sp. SB2 was cultured in industrial park wastewater, it could grow well either under air or 3% CO2 aeration, and it showed highest lipid productivity (64 mg/L/d) under 3% CO2 at sixth day and lower lipid productivity (29 mg/L/d) under air at seventh day.
The effects of different CO2 concentrations on growth and lipid accumulation of Monoraphidium sp. SB2 in 5L photobioreactors showed that it was exhibited lowest biomass production (0.27 g/L) under air aeration and highest biomass production of 1.92 g/L and 1.97 g/L under 10% and 15% CO2 aeration, respectively. The influences of different illumination on growth and lipid accumulation of Monoraphidium sp. SB2 in 5L photobioreactors showed that it was exhibited higher lipid content under 100 μmol/m2s illumination compared with 200 μmol/m2s illumination. Monoraphidium sp. SB2 showed highest lipid productivity under 200 μmol/m2s illumination and lowest lipid productivity under 100 μmol/m2s illumination. In energy conservation, Monoraphidium sp. SB2 showed higher lipid production /light intensity under 100 μmol/m2s illumination than others.
With the auto-adjustment on pH, the effect of the addition of the industrial park wastewaters on growth and lipid accumulation of Monoraphidium sp. SB2 in 5L photobioreactors showed that the biomass and lipid productivity of Monoraphidium sp. SB2 culturing in wastewaters with the addition of industrial park wastewaters were higher than that culturing in wastewaters without the addition of industrial park wastewaters and that culturing in industrial park wastewaters with the addition of 0.5mM acetate. Maximum biomass production and lipid content was 1.4 g/L and 30%, respectivity at day 9 and maximum biomass productivity and lipid productivity was 245 mg/L/d and 66.8 mg/L/d, respectivity at day 4. The addition of industrial park wastewaters seemed to positively impact the growth and lipid accumulation of Monoraphidium sp. SB2.
Chlorella sp. IWB-1 culturing in the industrial park wastewater showed highest biomass production (1.2g/L) at day 6, lower lipid content (15.5~16.7%) and highest lipid productivity (41.2 mg/L/d) at day 2.
Culturing in the industrial park wastewater, Chlorella sp. IWB-1 showed higher ammonium and phosphate uptake rate than Monoraphidium sp. SB2 did. The biomass production of Chlorella sp. IWB-1 were similar to that of Monoraphidium sp. SB2, but the lipid content of Chlorella sp. IWB-1 was lower than that of Monoraphidium sp. SB2 at day 6. Monoraphidium sp. SB2 showed higher CO2 fixed rate (6%) than Chlorella sp. IWB-1 did. Therefore the effect of CO2 bio-mitigation of Monoraphidium sp. SB2 was greater than that of Chlorella sp. IWB-1. Monoraphidium sp. SB2 showed higher ratios of biomass production to nitrogen consumption, biomass production to phosphours consumption, lipid production to nitrogen consumption, and lipid production to phosphours consumption than Chlorella sp. IWB-1 did. Therefore Monoraphidium sp. SB2 could produce more biomass and lipid accumulation but uptake less nitrogen and phosphours. The removal rate of nutrients by Chlorella sp. IWB-1 in wastewaters is better than that by Monoraphidium sp. SB2 because of its higher ammonium and phosphate uptake rates .
| Identifer | oai:union.ndltd.org:TW/103NCHU5087097 |
| Date | January 2015 |
| Creators | Li-Fen Wu, 吳麗芬 |
| Contributors | Chih-Jen Lu, 盧至人 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 159 |
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