Ma Ruijuan, Zhang Zhen, Fang Hong, Liu Xinyu, Ho Shih-Hsin, Xie Youping, Chen Jianfeng
Marine Biological Manufacturing Center of Fuzhou Institute of Oceanography, Fuzhou University, Fuzhou, 350108, China.
Technical Innovation Service Platform for High Value and High-Quality Utilization of Marine Organism, Fuzhou University, Fuzhou, 350108, China.
Biotechnol Biofuels Bioprod. 2023 Mar 15;16(1):47. doi: 10.1186/s13068-023-02300-8.
Chlorella sorokiniana FZU60 is a promising lutein producing microalga. A mixotrophy/photoautotrophy two-stage strategy can achieve high biomass concentration at stage 1 and high lutein content at stage 2, leading to excellent lutein production efficiency in C. sorokiniana FZU60. However, the underlying molecular mechanisms are still unclear, restraining the further improvement of lutein production.
In this study, physiological and biochemical analysis revealed that photochemical parameters (Fv/Fm and NPQ) and photosynthetic pigments contents increased during the shift from mixotrophy to photoautotrophy, indicating that photosynthesis and photoprotection enhanced. Furthermore, transcriptomic analysis revealed that the glyoxylate cycle and TCA cycle were suppressed after the shift to photoautotrophy, leading to a decreased cell growth rate. However, the gene expression levels of photosynthesis, CO fixation, autophagy, and lutein biosynthesis were upregulated at the photoautotrophy stage, demonstrating that microalgal cells could obtain more precursor to synthesize lutein for enhancing photosynthesis and reducing reactive oxygen species.
The findings help to elucidate the molecular mechanisms for high lutein production efficiency of C. sorokiniana FZU60 under the mixotrophy/photoautotrophy strategy, identify key functional genes responsible for lutein biosynthesis, and shed light on further improvement of lutein production by genetic or metabolic engineering in future studies.
索氏小球藻FZU60是一种很有潜力的产叶黄素微藻。混合营养/光合自养两阶段策略能够在第一阶段实现高生物量浓度，在第二阶段实现高叶黄素含量，从而使索氏小球藻FZU60具有出色的叶黄素生产效率。然而，其潜在的分子机制仍不清楚，这限制了叶黄素产量的进一步提高。
在本研究中，生理生化分析表明，从混合营养转变为光合自养过程中，光化学参数（Fv/Fm和NPQ）以及光合色素含量增加，这表明光合作用和光保护作用增强。此外，转录组分析显示，转变为光合自养后，乙醛酸循环和三羧酸循环受到抑制，导致细胞生长速率下降。然而，光合作用、CO固定、自噬和叶黄素生物合成的基因表达水平在光合自养阶段上调，表明微藻细胞可以获得更多前体来合成叶黄素，以增强光合作用并减少活性氧。
这些发现有助于阐明索氏小球藻FZU60在混合营养/光合自养策略下叶黄素生产效率高的分子机制，鉴定负责叶黄素生物合成的关键功能基因，并为未来研究中通过基因或代谢工程进一步提高叶黄素产量提供思路。
