Exploitation of microalgae for biotechnological applications

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2021-12
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Xie, Jiahui
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Wen, Zhiyou
Mendonca, Aubrey F
Yu, Chenxu
Wilson, Lester
Shi, Xiaolei
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Food Science and Human Nutrition
Abstract
Microalgae are an important biological resource that can yield a variety of high-value products. These products, including polyunsaturated fatty acids (PUFAs), pigments (e.g., phycobiliproteins), and other bioactive compounds, can be used in both nutritional and pharmaceutical applications. Meanwhile, in environmental biotechnology, microalgae are used for carbon dioxide (CO2) sequestration to reduce the CO2 concentration in the atmosphere. In this context, this dissertation illustrates how microalgae are cultivated and how the cultivation methods affect the production of high-value products such as proteins and fatty acids in microalgae, and also the applications of microalgae in biotechnology. This dissertation consists of three experiments organized by chapters modified from journal manuscripts. The first experiment investigated the effects of lighting conditions on the PE synthesis and PUFAs by the algae Rhodomonas salina (R. salina). A strategy of stepwise increasing light intensity was developed to achieve rapid cell growth and led to high PE and PUFAs production. This work demonstrated that light intensity plays an important role in the culture of R. salina for simultaneous production of PE and PUFAs. The second experiment explored the performance of revolving algal biofilm (RAB) coupling with the atomized liquid system in affecting algae CO2 bio-fixation under different CO2 concentrations. The results showed that atomizing system can greatly increase the CO2 mass transfer from gas to liquid for assisting the growth of microalgae. Compared with the single RAB system, the CO2 fixation rate is about 2.3 times, 1.2 times, and 1.3 times higher of the coupling system under 4%, 10%, and 20% CO2, respectively. The third experiment studied the performance of Anabaena sp. in using human urine as the medium to grow at batch, fed-batch, and semi-continuous cultivation processes. The results showed that 1:200 diluted urine medium can support the batch growth of Anabaena sp. in avoiding the ammonia/ammonium toxicity. Fed-batch and semi-continuous cultivation can further enhance the biomass production of Anabaena sp..
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