This study aimed to optimize growth medium composition for enhanced lipid and fatty acid production by the green halophilic chlorophyte Tetraselmis elliptica. The impact of different ratios of natural seawater, nitrogen source/concentration, carbon source/concentration, and trace metals on the growth, biomolecules, lipid accumulation, and lipid productivity was studied. In addition, fatty acid profile of the optimized growth medium was compared with that of the typical medium as a control, and biodiesel production as well as essential polyunsaturated fatty acids (PUFAs) were evaluated. Among all studied factors, 0.1 g L⁻¹ KNO₃, 0.01 g L⁻¹ glycerol, and 7.0 mg L⁻¹ FeSO₄·7H₂O significantly enhanced the lipid productivity of T. elliptica, and were used further to evaluate the impact of their combination. Cultivation of T. elliptica in the optimized medium showed enhancement of growth up to 16 days, which resulted in 30.9% and 17% increase in biomass and lipid productivities, respectively. Moreover, optimization of growth medium enhanced PUFAs proportion to 15.05% due to de novo synthesis of arachidonic acid and docosahexaenoic acids which represented 4.17% and 10.88%, respectively, of total fatty acids. Biodiesel characteristics of the optimized medium showed compliance of all studied parameters with the US standards. The present study provides new insights for commercial utilization of marine microalgae cultivated in optimized growth medium for dual purpose of ω-fatty acids and biodiesel production through biorefinery approach.

Graphical abstract

中文翻译：

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高盐生物柴油微藻 Tetraselmis elliptica 通过生长培养基优化增强脂质生产和必需 ω-脂肪酸合成

本研究旨在优化生长培养基的组成，以提高绿色嗜盐叶绿素Tetraselmis elliptica的脂质和脂肪酸产量。研究了天然海水、氮源/浓度、碳源/浓度和微量金属的不同比例对生长、生物分子、脂质积累和脂质生产力的影响。此外，将优化的生长培养基的脂肪酸谱与作为对照的典型培养基的脂肪酸谱进行了比较，并评估了生物柴油的产量以及必需的多不饱和脂肪酸 (PUFA)。在所有研究的因素中，0.1 g L ^-1 KNO ₃、0.01 g L ^-1甘油和7.0 mg L ^-1 FeSO ₄ ·7H₂ O显着提高了椭圆球藻的脂质生产力，并进一步用于评估它们组合的影响。T. elliptica的栽培在优化的培养基中显示出生长增强长达 16 天，这导致生物量和脂质生产力分别增加了 30.9% 和 17%。此外，由于花生四烯酸和二十二碳六烯酸的从头合成（分别占总脂肪酸的 4.17% 和 10.88%），生长培养基的优化将 PUFA 的比例提高到 15.05%。优化培养基的生物柴油特性表明所有研究参数均符合美国标准。本研究为在优化的生长培养基中培养的海洋微藻的商业利用提供了新的见解，用于通过生物精炼方法生产 ω-脂肪酸和生物柴油。

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