Dissertation
EXPLORING POSSIBILITIES FOR INCREASING ACCUMULATION OF STRUCTURAL CAROTENOID THROUGH SYNTHETIC BIOLOGY
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2021
DOI:
https://doi.org/10.7273/000005419
Handle:
https://hdl.handle.net/2376/119104
Abstract
Enhancing the accumulation of the structural pigment, lutein, in microalgae has been proven challenging. Strategies are needed to address the possible limitations of microalgae as a practical lutein producer. The capacity of lutein sequestration may determine the upper limit of cellular lutein content. The preliminary finding suggests that the light-harvesting complex (LHC) cannot provide enough capacity to sequester 2% dry cell weight (DCW) of lutein in microalgae species. Storing lutein in a lipophilic environment is a mechanism for achieving high lutein content, but several critical barriers must be overcome. However, the sequestration of lutein in an oil environment is attainable due to new developments in synthetic biology. Investigating similar mechanisms using model yeast strains such as Yarrowia lipolytica, with its relatively simple cell structure and more mature genetic engineering toolbox, could accelerate the achievement of this goal. To demonstrate this strategy, a zeaxanthin-producing pathway has been constructed in Yarrowia lipolytica as a platform to investigate the carotenoid sequestration mechanism. Three different kinds of crtZ genes were characterized for zeaxanthin production. The effect of overexpression of the crtZ gene on zeaxanthin production was examined. Through the overexpression of the optimum crtZ gene, the yield of zeaxanthin increased 4 folds, and a 721% increase in the content of zeaxanthin was observed. The optimum zeaxanthin yield and content were achieved 21.98 ± 1.80 mg/L and 3.20 ± 0.11 mg/g after engineering.
Carotenoid esterification genes XAT and PYP1 were expressed in the engineered Yarrowia lipolytica described above. However, zeaxanthin esters or other carotenoid esters were not detected in all transformants. Nonetheless, a β-carotene-rich transformant (XAT-2) was isolated. The induction of olive oil on the accumulation of β-carotene in XAT-2 was investigated. Under the induction of olive oil, the β-carotene content was 3.01-fold to 4.77-fold higher than control. The results suggest a possible new function of XAT on the β-carotene production. Exploring the new function of XAT might provide direction to enhance carotenoid accumulation in microorganisms.
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Details
- Title
- EXPLORING POSSIBILITIES FOR INCREASING ACCUMULATION OF STRUCTURAL CAROTENOID THROUGH SYNTHETIC BIOLOGY
- Creators
- Yuxiao Xie
- Contributors
- Shulin Chen (Advisor)Manuel Garcia-Pérez (Committee Member)Amit Dhingra (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
- Publisher
- Washington State University
- Number of pages
- 194
- Identifiers
- 99900592155201842
- Language
- English
- Resource Type
- Dissertation