The effect of switching environmental conditions on content and structure of lipid produced by a wild strain Picochlorum sp.

Continuous culture mode at the dilution rate D = 0.6 d(-1), allowed higher biomass and lipid productivities of Picochlorum sp. than batch culture. When the biomass of outflow was transferred in stressful batch cultures, highest yields of lipids ranging from 499 to 698 g kg(-1) (dw) were obtained under different nitrogen sources. The results indicated that highest polyunsaturated fatty acids (PUFAs) rates ranging from 68.7 to 78.8% were obtained under NaNO3 depletion, repletion, NaNO3 repletion, CO2 supplementation and NaH2PO4 depletion. Highest saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) rates ranging from 68.7 to 87.8% were obtained under phosphorus starvation and urea addition (-P + Ur), phosphorus starvation and ammonium addition (-P + Am), urea addition (Ur), ammonium addition (Am) and combined urea and ammonium addition (Ur + Am). Under (-P + Ur) and (-P + Am) stressful conditions, lipid profiles suitable for biodiesel production, were dominated by (C16:0 and C18:1). Results showed that combined nitrogen repletion and phosphorous depletion stress increased the synthesis of suitable fatty acid methyl esters (FAME) for biodiesel production. (C) 2018 Elsevier Ltd. All rights reserved.