Microalgae can accumulate substantial amounts of triacylglycerol, the primary feedstock for biodiesel production, under different stress conditions. In this study, exposure to alkaline pH (pH 10) using carbonate-bicarbonate buffer, nitrogen starvation, and both were applied to induce triacylglycerol accumulation in Auxenochlorella protothecoides KP7. In addition to triacylglycerol accumulation, growth, biochemical composition, and fatty acid profiles were examined in detail and compared. Our results illustrated that the combination of nitrogen starvation and alkaline pH led to significant increases in triacylglycerol and starch contents and drastic decreases in chlorophyll and protein contents compared with their control levels. Triacylglycerol levels, the triacylglycerol/total lipid ratio, and lipid productivities were significantly increased after 7 days of cultivation under the combined stress compared with the effects of nitrogen starvation alone. After prolonged cultivation under the combined stress, triacylglycerol content reached up to 25.01% of the dry cell weight and constituted up to 81.25% of total lipids. Under the combined stress, the major fatty acids in the total lipid of A. protothecoides KP7 were C18:1 (57.5%), C18:2 (19.5%), C16:0 (12.5%), and C18:3 (5.6%), and the percentages of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids represented 16.3, 58.4, and 25.1% of the total fatty acids, respectively. Furthermore, the combined stress was associated with the lowest iodine value (97.64 g I₂ (100 g)⁻¹), highest oxidative stability (7.29 h), and highest cetane number (55.26) among the examined conditions. The use of nitrogen-free medium containing carbonate-bicarbonate buffer for cultivation appears promising for enhancing triacylglycerol production in A. protothecoides.

在不同的压力条件下，微藻类可以积累大量的三酰基甘油，这是生物柴油生产的主要原料。在这项研究中，使用碳酸盐-碳酸氢盐缓冲液暴露于碱性pH（pH 10），氮饥饿和二者均被用于诱导原水小球藻中的三酰基甘油积累。KP7。除了三酰基甘油的积累外，还对生长，生化组成和脂肪酸谱进行了详细检查和比较。我们的结果表明，与对照组相比，氮饥饿和碱性pH值的组合导致三酰基甘油和淀粉含量显着增加，叶绿素和蛋白质含量显着下降。与单独氮饥饿的影响相比，在联合胁迫下培养7天后，三酰甘油水平，三酰甘油/总脂质比率和脂质生产率显着提高。在联合胁迫下长时间培养后，三酰基甘油含量达到干细胞重量的25.01％，占总脂质的81.25％。在联合胁迫下，总脂中的主要脂肪酸A. protothecoides的KP7为C18：1（57.5％），C18：2（19.5％），C16：0（12.5％）和C18：3（5.6％），以及饱和脂肪酸，单不饱和脂肪酸的百分比，多不饱和脂肪酸分别占总脂肪酸的16.3％，58.4％和25.1％。此外，在所检查的条件下，组合应力与最低碘值（97.64 g I ₂（100 g）^-1），最高氧化稳定性（7.29 h）和最高十六烷值（55.26）相关。含有碳酸氢盐-碳酸氢盐缓冲液的无氮培养基用于培养似乎有望提高原球藻中三酰甘油的产量。