Growth and high-valued products accumulation characteristics of microalgae in saline-alkali leachate from Inner Mongolia

In this study, the growth and high-valued products accumulation characteristics of three common high-valued microalgae (Chlorella sp. HQ, Scenedesmus sp. LX1, and Chlorella vulgaris) in saline-alkali leachate were compared to select the species with greatest utilization potential. The results showed that after 28 days of cultivation, among three microalgae, Chlorella sp. HQ grew best with its maximum density at peak of 1.16 × 10⁷ cells mL⁻¹ and lipid production per unit cell (0.047 ± 0.006 × 10⁻⁷ mg cell⁻¹) and lipid content (18.18 ± 3.14%) were largest. The triacylglycerol (TAG) yield and content of Scenedesmus sp. LX1 were the highest, reaching 0.005 ± 0.000 × 10⁻⁷ mg cell⁻¹ and 19.74 ± 2.53%, respectively, which was slightly higher than those of Chlorella sp. HQ. According to comprehensive comparison, Chlorella sp. HQ was most suitable to grow in the saline-alkali leachate in terms of algal density, lipid yield, and content. The potential comparison and effects of salinity on the high-valued products accumulation of Chlorella sp. HQ compared with those in SE standard medium, reclaimed water, and tap water were further carried out. It was found that the density order of Chlorella was saline-alkali leachate > SE medium > reclaimed water > tap water. And the Chlorella density in the leachate with a salinity of 0.14% was greater than the other three salinities (0.32%, 0.45%, and 0.6%) at the end of cultivation. While the maximum lipid yield per unit cell and lipid content of Chlorella occurred in the salinity of 0.6%, which indicated that high salinity promoted the accumulation of lipid. Furthermore, other high-valued products (including starch, protein, total sugar, and photosynthetic pigments) accumulation characteristics were analyzed and found that they were all superior than those in SE medium. And with the salinity decreased, the microalgal protein and starch contents decreased. The contents of photosynthetic pigment and total sugar reached a maximum at salinities of 0.32% and 0.45%, respectively.