| Summary: | 碩士 === 國立中正大學 === 化學工程研究所 === 102 === The characteristics of microalgae are nutrient-rich, strong environmental adaptability, growth rate fast and easy to culture. This microalgae can grow by photosynthetic that is converted water and carbon dioxide into biomass using light as an energy source. In nutrient-adequate cultivate environment, the light is major limiting factor which affecting the growth of microalgae. In the study, Nannochloropsis oculata was cultured in 2X modified Walne’s medium by photobioreactor. The effect of light intensity and tolerance of carbon dioxide was investigated during fed-batch cultivation.
In order to studied the effect of light intensity the result demonstrated that the illuminated three different light intensity was separately used to studied as 4000, 10,000 and 40,000 Lux under a photoperiod of 12 hr (light):12 hr (dark) cycle and included air (0.03%CO2). An N. oculata biomass concentration of 0.545 g dry wt/L and specific growth rate of 0.192 d-1 were achieved when the microalgae was illuminated 40,000 Lux. This result showed that the maximum biomass yield of N. oculata was obtained at 40,000 Lux of illuminated the light intensity under fed-batch cultivation condition. Therefore, the fed-batch cultivation using the high light intensity illumination was suitable.
For the effect of carbon dioxide, the tolerance capability of carbon dioxide of N. oculata was studied under light intensity of 40,000 Lux. N. oculata cultivation was aerated with different CO2 concentrations including 0.03% (air), 2%, 5%, 7.5%, 10% and 15% CO2. Results showed that the N. oculata cultivation at 2% CO2 could yield the maximum biomass of 2.240 g/L and the maximum specific growth rate of 0.328 d-1. Moreover, the N. oculata could grow at CO2 concentration as high as 15%. The biomass and specific growth rate achieved at 1.518 g dry wt/L and 0.288 d-1, respectively. When aerated with 2% CO2, the use of 40,000 Lux of light intensity promoted the production of biomass in 2.43 and 3.11 times, in comparison with 10,000 Lux and 4000 Lux of light intensity, respectively. In conclusion, the high light intensity could enhance microalgae photosynthetic efficiency. Also, the cultivation at 2% CO2 could enhance growth rate of N. oculata and reduce the mutual shading effect. Therefore, microalgae cells could be cultivated to high cell density at the conditions of 2% CO2 and 40000 Lux of light intensity. Moreover, N. oculata could tolerate high CO2 concentration, suggesting that this microalgae could be used for capturing CO2 from industrial process.
Finally, the gene of trehalose synthase from Pseudomonas putida F1 was amplified and cloned into a plasmid vector. The restlant recombinant plasmid pRBCptH-TS was then transformed to N. oculata by electroporation. Four stains of recombinant N. oculata were screend from the plate containing antibiotics in Walne medium.
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