title: Hyperosmosis and its combination with nutrient-limitation are novel environmental stressors for induction of triacylglycerol accumulation in cells of Chlorella kessleri.
abstract: Triacylglycerols of oleaginous algae are promising for production of food oils and biodiesel fuel. Air-drying of cells induces triacylglycerol accumulation in a freshwater green alga, Chlorella kessleri, therefore, it seems that dehydration, i.e., intracellular hyperosmosis, and/or nutrient-limitation are key stressors. We explored this possibility in liquid-culturing C. kessleri cells. Strong hyperosmosis with 0.9 M sorbitol or 0.45 M NaCl for two days caused cells to increase the triacylglycerol content in total lipids from 1.5 to 48.5 and 75.3 mol%, respectively, on a fatty acid basis, whereas nutrient-limitation caused its accumulation to 41.4 mol%. Even weak hyperosmosis with 0.3 M sorbitol or 0.15 M NaCl, when nutrient-limitation was simultaneously imposed, induced triacylglycerol accumulation to 61.9 and 65.7 mol%, respectively. Furthermore, culturing in three-fold diluted seawater, the chemical composition of which resembled that of the medium for the combinatory stress, enabled the cells to accumulate triacylglycerol up to 24.7 weight% of dry cells in only three days. Consequently, it was found that hyperosmosis is a novel stressor for triacylglycerol accumulation, and that weak hyperosmosis, together with nutrient-limitation, exerts a strong stimulating effect on triacylglycerol accumulation. A similar combinatory stress would contribute to the triacylglycerol accumulation in air-dried C. kessleri cells.
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Horinouchi, Hachioji, Tokyo 192-0392, Japan.
authors.forename: Kazuho
authors.initials: K
authors.lastname: Hirai
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Horinouchi, Hachioji, Tokyo 192-0392, Japan.
authors.forename: Taihei
authors.initials: T
authors.lastname: Hayashi
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Horinouchi, Hachioji, Tokyo 192-0392, Japan.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Hasegawa
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Horinouchi, Hachioji, Tokyo 192-0392, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Sato
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Horinouchi, Hachioji, Tokyo 192-0392, Japan.|JST, Chiyoda-ku, Tokyo 102-0075, Japan.
authors.forename: Mikio
authors.initials: M
authors.lastname: Tsuzuki
authors.affiliation: School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Horinouchi, Hachioji, Tokyo 192-0392, Japan.|JST, Chiyoda-ku, Tokyo 102-0075, Japan.
authors.forename: Norihiro
authors.initials: N
authors.lastname: Sato
mesh_terms: D002478:Cells, Cultured; D002696:Chlamydomonas / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D002708:Chlorella / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D004777:Environment; D009584:Nitrogen / Q000494:pharmacology*; D009995:Osmosis / Q000187:drug effects; D010758:Phosphorus / Q000494:pharmacology*; D012623:Seawater; D012965:Sodium Chloride / Q000494:pharmacology; D013012:Sorbitol / Q000494:pharmacology; D013312:Stress, Physiological / Q000187:drug effects*; D014280:Triglycerides / Q000378:metabolism*
chemical_list: D014280:Triglycerides; D010758:Phosphorus; D012965:Sodium Chloride; D013012:Sorbitol; D009584:Nitrogen