Patel College of Global Sustainability, University of South Florida, 4202 E. Fowler Avenue, Tampa, FL 33620, USA.
Sci Total Environ. 2021 Dec 15;800:149504. doi: 10.1016/j.scitotenv.2021.149504. Epub 2021 Aug 5.
The inherent metabolic versatility of Chlorella vulgaris that enables it to metabolize both inorganic and organic carbon under various trophic modes of cultivation makes it a promising candidate for industrial applications. To shed light on the metabolic flexibility of this microalga, time resolved proteomic and metabolomic studies were conducted in three distinct trophic modes (autotrophic, heterotrophic, mixotrophic) at two growth stages (end of linear growth at 6 days and during nutrient deprivation at 10 days). Sweet sorghum bagasse (SSB) hydrolysate was supplied to the cultivation medium as a renewable source of organic carbon mainly in the form of glucose. Integrated multi-omics data showed improved nitrogen assimilation, re-allocation, and recycling and increased levels of photosystem II (PS II) proteins indicating effective cellular quenching of excess electrons during mixotrophy. As external addition of organic carbon (glucose) to the cultivation medium decreases the cell's dependence on photosynthesis, an upregulation in the mitochondrial electron transport chain was recorded that led to increased cellular energy generation and hence higher growth rates under mixotrophy. Moreover, upregulation of the lipid-packaging proteins caleosin and 14_3_3 domain-containing protein resulted in maximum expression during mixotrophy suggesting a strong correlation between lipid synthesis, stabilization, and assembly. Overall, cells cultivated under mixotrophy showed better nutrient stress tolerance and redox balancing leading to higher biomass and lipid production. The study offers a panoramic view of the microalga's metabolic flexibility and contributes to a deeper understanding of the altered biochemical pathways that can be exploited to enhance algal productivity and commercial potential.
小球藻具有固有的代谢多功能性，使其能够在各种培养的营养模式下代谢无机碳和有机碳，这使其成为工业应用的有前途的候选物。为了阐明这种微藻的代谢灵活性，在三种不同的营养模式（自养、异养、混合营养）下，在两个生长阶段（6 天的线性生长结束和 10 天的营养剥夺期间）进行了时间分辨的蛋白质组学和代谢组学研究。甜高粱蔗渣（SSB）水解物作为可再生的有机碳源供应给培养培养基，主要以葡萄糖的形式供应。综合多组学数据表明，氮的同化、再分配和再循环得到了改善，并且光合作用系统 II（PS II）蛋白的水平增加，表明在混合营养期间，细胞有效地淬灭了过量的电子。由于向培养培养基中添加有机碳（葡萄糖）会降低细胞对光合作用的依赖，因此记录到线粒体电子传递链的上调，这导致在混合营养下细胞产生更多的能量，从而获得更高的生长速率。此外，脂质包装蛋白 caleosin 和含有 14_3_3 结构域的蛋白的上调导致在混合营养下达到最大表达，这表明脂质合成、稳定和组装之间存在很强的相关性。总的来说，在混合营养下培养的细胞表现出更好的营养胁迫耐受性和氧化还原平衡，从而导致更高的生物量和脂质产量。该研究提供了微藻代谢灵活性的全景图，并有助于更深入地了解可以利用的改变的生化途径，以提高藻类的生产力和商业潜力。
