RESULTS: Cells cultivated with 10% CO2 exhibited significantly better growth and lipid accumulation rates, achieving up to 2.5-fold higher cell density and twice the lipid content by day 7. To understand the relationship between CO2 concentrations and phenotypes, transcriptomic analysis was conducted across different CO2 conditions and growth phases. According to the analysis of differentially expressed genes and gene ontology, Chlorella sp. ABC-001 exhibited the development of chloroplast organelles during the early exponential phase under high CO2 conditions, resulting in improved CO2 fixation and enhanced photosynthesis. Cobalamin-independent methionine synthase expression was also significantly elevated during the early growth stage, likely contributing to the methionine supply required for various metabolic activities and active proliferation. Conversely, the cells showed sustained repression of carbonic anhydrase and ferredoxin hydrogenase, involved in the carbon concentrating mechanism, throughout the cultivation period under high CO2 conditions. This study also delved into the transcriptomic profiles in the Calvin cycle, nitrogen reductase, and lipid synthesis. Particularly, Chlorella sp. ABC-001 showed high expression levels of genes involved in lipid synthesis, such as glycerol-3-phosphate dehydrogenase and phospholipid-diacylglycerol acyltransferase. These findings suggest potential targets for metabolic engineering aimed at enhancing lipid production in microalgae.
CONCLUSIONS: We expect that our findings will help understand the carbon concentrating mechanism, photosynthesis, nitrogen assimilation, and lipid accumulation metabolisms of green algae according to CO2 concentrations. This study also provides insights into systems metabolic engineering of microalgae for improved performance in the future.
结果:用10%CO2培养的细胞表现出明显更好的生长和脂质积累速率,到第7天,细胞密度可提高2.5倍,脂质含量可提高两倍。为了理解CO2浓度和表型之间的关系,在不同的CO2条件和生长阶段进行转录组学分析。根据差异表达基因和基因本体论的分析,小球藻sp.ABC-001在高CO2条件下的早期指数期表现出叶绿体细胞器的发育,从而改善CO2固定和增强光合作用。不依赖钴胺的蛋氨酸合成酶表达在早期生长阶段也显著升高,可能有助于各种代谢活动和活跃增殖所需的蛋氨酸供应。相反,细胞表现出碳酸酐酶和铁氧还蛋白氢化酶的持续抑制,参与碳浓缩机制,在高CO2条件下的整个栽培期间。这项研究还深入研究了卡尔文循环中的转录组概况,氮还原酶,和脂质合成。特别是,小球藻sp.ABC-001显示参与脂质合成的基因的高表达水平,例如甘油-3-磷酸脱氢酶和磷脂-二酰甘油酰基转移酶。这些发现提示了旨在增强微藻中脂质产生的代谢工程的潜在目标。
结论:我们希望我们的发现将有助于理解碳浓缩机制,光合作用,氮同化,和根据CO2浓度的绿藻的脂质积累代谢。这项研究还为微藻的系统代谢工程提供了见解,以改善未来的性能。