Regulatory carbon metabolism underlying seawater-based promotion of triacylglycerol accumulation in Chlorella kessleri

• Published in: Bioresource technology Vol. 289; p. 121686
• Main Authors: Otaki, Rie, Oishi, Yutaro, Abe, Seiya, Fujiwara, Shoko, Sato, Norihiro
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.10.2019
• Subjects: Carbon metabolism; Chlorella kessleri; Gene expression; Seawater-based biofuel; Triacylglycerol; Carbon metabolism; Triacylglycerol; Chlorella kessleri; Gene expression; Seawater-based biofuel
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2019.121686

•Seawater-like culture of Chlorella produced >20% dry cell weight triacylglycerol.•Nutrient-limitation induced lipid production with eukaryotic pathway being activated.•Nutrient-limitation induced protein synthesis repression and starch degradation.•Hyperosmosis reinforced this particular C-metabolism nutrient-limitation induced.•Gene expression was enhanced concerning lipid synthesis and starch degradation. Chlorella kessleri accumulates triacylglycerol usable for biodiesel-fuel production to >20% dry cell weight in three days when cultured in three-fold diluted seawater, which imposes the combinatory stress of hyperosmosis and nutrients limitation. The quantitative behavior of major C-compounds, and related-gene expression patterns were investigated in Chlorella cells stressed with hyperosmosis, nutrients limitation, or their combination, to elucidate the C-metabolism for economical seawater-based triacylglycerol accumulation. Combinatory-stress cells showed repressed protein synthesis with initially accumulated starch being degraded later, the C-metabolic flow thereby being diverted to fatty acid and subsequent triacylglycerol accumulation. This C-flow diversion was induced by cooperative actions of nutrients-limitation and hyperosmosis. Semi-quantitative PCR analysis implied positive rewiring of the diverted C-flow into triacylglycerol in combinatory-stress cells through upregulation of gene expression concerning fatty acid and triacylglycerol synthesis, and starch synthesis and degradation. The information of regulatory C-metabolism will help reinforce the seawater-based triacylglycerol accumulation ability in algae including Chlorella.