Effect of temperature and nitrogen concentration on biomass composition of Heterochlorella luteoviridis

Abstract The interest in microalga as a food supplement has grown due their high contents of carotenoids, polyunsaturated fatty acids and proteins. This study evaluated the effect of different temperatures (22, 27 or 32 °C) and sodium nitrate concentrations (12, 24, 36, 48 or 60 mg L-1 of N-NO3) in culture medium on Heterochlorella luteoviridis biomass production and composition. The highest biomass concentration (3.35 g L-1) was observed at the highest N-NO3 concentration. The N-NO3 concentration positively affected protein, carbohydrate and carotenoids contents of biomass. On the other hand, cells cultured at the lowest N-NO3 concentration showed a slight increment in lipid content. The major carotenoid was lutein (30.7 ± 1.4% of total carotenoids), and the polyunsaturated fatty acids were 37 ± 2% of total fatty acids. Low temperature improved the biosynthesis of ω3 type fatty acids by lowering the ω6:ω3 ratio. Overall, our results indicate H. luteoviridis can yield high biomass concentration under autotrophic growth, resulting in a biomass rich in carotenoids, mainly lutein, and ω3 polyunsaturated fatty acids.摘要：微藻作为食品补充剂的关注度日益提升，这归因于其富含类胡萝卜素、多不饱和脂肪酸与蛋白质。本研究探究了培养温度（22、27或32 ℃）及培养基中硝酸钠浓度（12、24、36、48或60 mg·L⁻¹，以N-NO₃计）对异养小球藻（Heterochlorella luteoviridis）生物量生产与组分的影响。最高生物量浓度（3.35 g·L⁻¹）出现在最高硝酸钠浓度组。硝酸钠浓度对生物量中的蛋白质、碳水化合物与类胡萝卜素含量均存在正向影响。反之，在最低硝酸钠浓度下培养的细胞，其脂质含量略有提升。该藻的主要类胡萝卜素为叶黄素（占总类胡萝卜素的30.7 ± 1.4%），多不饱和脂肪酸占总脂肪酸的37 ± 2%。较低的培养温度可通过降低ω6:ω3比值，促进ω3型脂肪酸的生物合成。综上，本研究结果表明，异养小球藻在自养生长条件下可获得较高的生物量浓度，所得生物量富含类胡萝卜素（主要为叶黄素）与ω3型多不饱和脂肪酸。