Influence of temperature and nutrient content on lipid production in freshwater microalgae cultures

The production of biomass by microalgae is considered a clean alternative compared to other plant crops that require large areas for cultivation and that generate environmental impacts. This study evaluated the influence of temperature and nutrients on lipid contents of cultured species of freshwater microalgae, with a view toward using these lipids for biodiesel production. Two strains of Monoraphidium contortum, a culture containing Chlorella vulgaris and Desmodesmus quadricauda and another strain of Microcystis aeruginosa were maintained in the laboratory for six days, in five culture media: modified ASM-1 (control, with high concentrations of phosphate and nitrate; phosphorus-deficient; non-limiting phosphate; nitrogen-deficient; and non-limiting nitrate). The cultures were then exposed to temperatures of 13°C, 25°C (control) and 37°C for eight days (n=3). Lipids were extracted by the cold-solvent (methanol and chloroform) method. On average, the highest total lipid yields were observed when the strains were maintained at 13°C and in the non-limiting nitrate medium. The lipid percentage varied depending on the concentration of algal biomass. This study showed that manipulation of controlling factors can increase the lipid concentration, optimizing the total production in order to use this raw material for biodiesel.相较于需占用大片种植面积且易造成环境影响的其他农作物，微藻生物质生产被视为一种清洁替代方案。本研究评估了温度与营养盐对淡水微藻培养株系脂质含量的影响，以期将此类脂质应用于生物柴油生产。将两株扭弯单针藻（Monoraphidium contortum）、一株含普通小球藻（Chlorella vulgaris）与四尾集星藻（Desmodesmus quadricauda）的混合培养物，以及另一株铜绿微囊藻（Microcystis aeruginosa）置于实验室环境中，于五种培养基内培养六天：改良ASM-1培养基（对照组：高磷酸盐与硝酸盐浓度；缺磷培养基；非限磷培养基；缺氮培养基；非限氮培养基）。随后将各培养物置于13℃、25℃（对照组）与37℃的环境下培养八天（n=3）。采用冷溶剂（甲醇与氯仿）法提取脂质。平均结果显示，当藻株培养于13℃环境与非限氮培养基中时，总脂质产率达到最高。脂质百分比随藻类生物质浓度的变化而发生波动。本研究证实，通过调控相关影响因素可提升脂质浓度，优化总产物产量，从而将该原料用于生物柴油生产。