Dissertation
SYNERGY OF PHOTOSYNTHESIS AND CARBON METABOLISM IN MICROALGAL GROWTH AND BIOSYNTHESIS UNDER MIXOTROPHIC CONDITIONS
Doctor of Philosophy (PhD), Washington State University
01/2019
Handle:
https://hdl.handle.net/2376/111702
Abstract
Mixotrophic culture of microalgae is gaining increasing attentions because of the unique metabolic capability of using both photosynthesis and organic carbon metabolism. Mixotrophic culture leads to higher productivity than either phototrophic or heterotrophic process alone. There are both opportunities and challenges to meet the increasing demand for cost-effective process of microalgae culture. In this dissertation study, two organic carbons, ribose (C5) and gluconate (C6) were first investigated for improving biomass concentration and cell activity of H. pluvialis under mixotrophic conditions. Biomass content under the culture fed with gluconate increased five-folds over that of heterotrophic culture. Additionally, the microalgae showed good high-light tolerance and effective photosynthesis at high light intensity.
The synergism of photosynthesis and C5 metabolism in H. pluvialis was revealed under mixotrophic culture conditions. H. pluvialis with ribose showed significantly active cell division and motility. Doubled photosynthetic rate of the algae with ribose was obtained comparing with that of phototrophic culture, which was contributed by effective Calvin cycle with energy supply from enlarged PS I and additional substrates crossing from ribose metabolism. The better understanding of interaction of photosynthesis and C5 metabolism offers a promising route for improving algal biomass and bioproducts content.
Additionally, multilevel heuristic LED regimes were designed to further enhance biomass and bioproducts production of H. pluvialis. The highest astaxanthin (3.3%) and protein content (45.4%) were induced by the white-blue light regime. White-red regime was more favorable for enhancing algal growth and lipid synthesis than blue light. Optimal light protocol can be developed synergistically with the difference in adaptation and tolerance of algal cell in terms of morphology and physiology.
Cost-effective microalgae production can only be implemented with both high productivity and conservation of nutrients. A new extremophilic microalga Chlorella vulgaris CA1 with high-ammonia tolerance was isolated in this study. Protein-rich biomass was grown with reusing nutrients from dairy wastewater. 96% nitrogen and 79% phosphorus in the wastewater were effectively removed with the microalgae culture. These findings suggest the potential of mixotrophic microalgae culture for enhancement of growth and bioproducts production and application in wastewater treatment.
Metrics
106 File views/ downloads
26 Record Views
Details
- Title
- SYNERGY OF PHOTOSYNTHESIS AND CARBON METABOLISM IN MICROALGAL GROWTH AND BIOSYNTHESIS UNDER MIXOTROPHIC CONDITIONS
- Creators
- Na Pang
- Contributors
- Shulin Chen (Advisor)Helmut Kirchhoff (Committee Member)Hanwu Lei (Committee Member)Sanja Roje (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Biological Systems Engineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 172
- Identifiers
- 99900581814901842
- Language
- English
- Resource Type
- Dissertation