Energy is one of the key issues of sustainable development of human society. Biomass and lipid, the accumulated products in microalgae through photosynthesis, can be used for the production of new clean energy, which is the basis for the third generation of biofuels. From the year of 2011, cooperated with Prof. RONG Junfeng from SINOPEC Research Institute of Petroleum Processing, researchers from the Research Group of Algal Biochemistry at Institute of Hydrobiology, Chinese Academy of Sciences (IHB) has made a series of achievements in the research on microalgal biofuels and the mechanisms of lipid metabolism and energy signal-regulation in oil-producing microalgae.   

By using informatics-based analytic technique, IHB researchers retrieved and systematically analyzed the published manuscripts and patents related to microalgal biofuels and microalgae applied to biological sequestration of industrial flue gases between 1900 and mid-2015. They deemed that high capital and operating costs would be the key impediment to limit commercial applications of algae-based biodiesel.    

In future R&D activities, three proposals were presented: unremitting investments and policy supports are expected; the development of a more in-depth understanding of microalgal basic biology has more potential economic benefit than exemplary large-scale outdoor research; integrated application of microalgal biotechnology in industrial flue gases sequestration and wastewater treatment combined with microalgal biofuel production could be a possible solution (Applied Energy 2015; Frontiers in Energy Research 2014).    

Based on the studies on lipid formation in oil-producing alga, researchers proposed the coupling mechanism of nitrogen starvation induced neutral lipid accumulation and oxidative stress, and suggested the possible role for cyclic electron flow in ATP supply for nitrogen starvation-induced lipid biosynthesis (PLoS ONE 2013; Frontiers in Energy Research 2015). Furthermore, they found the response and regulation mechanism of the Ca2+ signal in N starvation induce lipid synthesis (Plant Cell Physiology 2014).

Researchers from IHB further exploited these above conclusions in the model green alga Chlamydomonas reinhardtii, and proposed that photophosphorylation and respiratory oxidative phosphorylation, the main sources of ATP, are inhibited and there is a shortage of ATP when microalgae are exposed to N starvation, and Ca²⁺-regulated photosynthesis cyclic phosphorylation supplies ATP for nitrogen starvation-induced lipid biosynthesis. Based on these studies, a regulation model of neutral lipid synthesis in green alga subjected to N starvation is initially formed (Scientific Reports 2015).   

These works were jointly supported by the National Program on Key Basic Research Project, the National Natural Science Foundation of China, the Natural Science Foundation of Hubei Province of China, Sinopec, and the Knowledge Innovation Program of the Chinese Academy of Sciences.  

Figure: Regulation of neutral lipid synthesis in microalgae subjected to N starvation