Salt stress can be used to increase intracellular lipid content of microalgae. However, the growth of microalgae is decreased under salt stress. Thus, a two-stage cultivation strategy with a growth phase followed by a stress stage is required to improve lipid content. In this study, adaptive laboratory evolution (ALE) with salt stress was conducted to improve biomass and fatty acid (FA) productivity using a locally isolated freshwater microalga Parachlorella sp. in a single-stage cultivation. Algal cell growth and FA production under conditions of salt stress (0–40 g of NaCl/L) were compared to those in a 0.5 L bubble column photobioreactor and appropriate levels of salt stress (10 and 20 g/L) were determined for ALE. During the ALE process, the average cell size increased from 3.0 to 3.9 µm. After eight consecutive ALE cycles, microalgal growth rate was remarkably increased to close to that of the culture without salt stress. Furthermore, FA content in microalga was improved from 7.5% to 25%. This result was confirmed by observations with various types of microscopes. Eventually, overall FA productivity was increased up to 219.0 ± 10.7 mg/L/day with the addition of 20 g of NaCl/L, which was 233% greater than that of the culture without salt stress (93.8 ± 5.3 mg/L/day) due to increased FA content. Recovered biomass productivity was 80% of that in the culture without salt stress. These results suggest that microalgal FA production can be significantly improved by a simple ALE process without an additional stress culture step.

盐胁迫可用于增加微藻的细胞内脂质含量。但是，微藻的生长在盐胁迫下会降低。因此，需要两阶段的培养策略，即在生长期之后进行胁迫阶段，以提高脂质含量。在这项研究中，使用局部分离的淡水微藻对小球藻，进行了具有盐胁迫的适应性实验室进化（ALE），以提高生物量和脂肪酸（FA）的生产率。sp。在单阶段栽培中。将盐胁迫（0–40 g NaCl / L）下的藻细胞生长和FA产生与0.5 L气泡柱光生物反应器中的藻细胞生长和FA产生进行比较，并确定ALE的适当盐胁迫水平（10和20 g / L） 。在ALE过程中，平均孔尺寸从3.0微米增加到3.9微米。在连续八次ALE循环后，微藻的生长速度显着增加，接近无盐胁迫的培养物。此外，微藻中的FA含量从7.5％提高到25％。通过各种显微镜的观察证实了这一结果。最终，添加20 g NaCl / L可使总FA生产率提高至219.0±10.7 mg / L / day，这比无盐胁迫的培养物（93.8±5.3 mg / L / day）高233％ ）是由于增加了FA含量。在没有盐胁迫的情况下，回收的生物量生产力是培养物中生物量的80％。这些结果表明，通过简单的ALE工艺可以显着改善微藻FA的生产，而无需额外的压力培养步骤。