Copper is an important metal for industry, and its toxic threshold in natural ecosystems has increased since the industrial revolution. As an essential nutrient, it is required in minute amounts, being toxic in slightly increased concentrations, causing great biochemical transformation in microalgae. This study aimed at investigating the physiology of Scenedesmus quadricauda, a cosmopolitan species, exposed to copper concentrations including those that trigger intracellular biochemical modifications. The Cu exposure concentrations tested ranged from 0.1 to 25 µM, thus including environmentally important levels. Microalgae cultures were kept under controlled environmental conditions and monitored daily for cell density, in vivo chlorophyll a, and photosynthetic quantum yield (Φ_M). After 24 h growth, free Cu²⁺ ions were determined, and after 96 h, cellular Cu concentration, total carbohydrates, proteins, lipids, and cell volume were determined. The results showed that both free Cu²⁺ ions and cellular Cu increased with Cu increase in culture medium. Microalgae cell abundance and in vivo chlorophyll a were mostly affected at 2.5 µM Cu exposure (3.8 pg Cu cell⁻¹) and above. Approximately 31% decrease of photosynthetic quantum yield was obtained at the highest Cu exposure concentration (25 µM; 25 pg Cu cell⁻¹) in comparison with the control. However, at environmentally relevant copper concentrations (0.5 µM Cu; 0.4 pg Cu cell⁻¹) cell volume increased in comparison with the control. Considering biomolecules accumulation per unit cell volume, the highest carbohydrates and proteins yield was obtained at 1.0 µM Cu (1.1 pg Cu cell⁻¹), while for lipids higher Cu was necessary (2.5 µM Cu; 3.8 pg Cu cell⁻¹). This study is a contribution to the understanding of the effects of environmentally significant copper concentrations in the physiology of S. quadricauda, as well as to biotechnological approach to increase biomolecule yield in microalgae production.

铜是工业上的重要金属，自工业革命以来，铜在自然生态系统中的毒性阈值有所提高。作为必需的营养素，微量需要，微量浓度的有毒物质，会在微藻类中引起巨大的生化转化。这项研究的目的是调查世界性物种Scendesmus quadricauda（暴露于铜浓度下，包括引发细胞内生化修饰的铜浓度）的生理学。测试的铜暴露浓度范围为0.1至25 µM，因此包括对环境重要的水平。将微藻培养物保持在受控的环境条件下，并每天监测细胞密度，体内叶绿素a和光合量子产率（Φ_中号）。生长24小时后，测定了游离Cu ²⁺离子，在96 h后，测定了细胞中Cu的浓度，总碳水化合物，蛋白质，脂质和细胞体积。结果表明，随着培养基中Cu含量的增加，游离Cu ²⁺离子和细胞中Cu含量均增加。在2.5 µM Cu暴露（3.8 pg Cu cell ^-1）及以上时，微藻细胞的丰度和体内叶绿素a受到的影响最大。在最高的铜暴露浓度（25 µM； 25 pg铜电池^-1）下，光合量子产率降低了约31％）与控件进行比较。然而，与对照相比，在环境相关的铜浓度（0.5 µM Cu； 0.4 pg Cu细胞^-1）下，细胞体积增加。考虑到每单位细胞体积的生物分子积累，在1.0 µM Cu（1.1 pg Cu cell ^-1）下可获得最高的碳水化合物和蛋白质产量，而对于脂质，则需要更高的Cu（2.5 µM Cu； 3.8 pg Cu cell ^-1）。这项研究有助于理解环境中重要的铜浓度对S.quadricauda的生理学的影响，以及有助于提高微藻生产中生物分子产量的生物技术方法。