To investigate the possibility of culture medium reuse in large-scale industrial microalgae cultivation for the alleviation of the massive water requirement pressure, the aging forming process of Chlorella vulgaris growing medium was explored and the aged medium's inhibition mechanisms on cell growth were inspected. The results demonstrated that when the medium was continuously reused, the collected maximal C. vulgaris biomass decreased. After the fourth medium reuse, the maximal biomass concentration was only 55 ± 1.1% of that in the fresh medium, which indicated the gradual aging of the medium. Furthermore, the composition variation of the released organic secretions during the culture medium reuse was monitored and the results showed that high concentrations of fatty acids (FAs), including palmitic acid, stearic acid, and small amounts of polysaccharides, were accumulated. Further investigation indicated that the obtained maximal biomass of C. vulgaris has a negative relationship with the manually added initial FA concentrations in the medium which suggested that the accumulated FAs in the medium probably were the main C. vulgaris growth inhibition factor. The inhibition effect of FAs on C. vulgaris was mainly achieved via impacting the cells' photosynthesis efficiencies to destroy the intracellular antioxidant system.

中文翻译：

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小球藻生长培养基的老化形成过程及其抑制机制。

为了研究培养基在大规模工业微藻培养中再利用以减轻巨大的需水压力的可能性，探讨了小球藻生长培养基的老化形成过程，并研究了老化培养基对细胞生长的抑制机制。结果表明，当不断重复使用培养基时，所收集的最大梭状芽孢杆菌生物量下降。在第四次重复使用培养基后，最大生物量浓度仅为新鲜培养基中的55±1.1％，这表明培养基逐渐老化。此外，监测了培养基再利用过程中释放的有机分泌物的组成变化，结果表明，高浓度的脂肪酸（FAs），包括棕榈酸，硬脂酸，并积累了少量的多糖。进一步的研究表明，所获得的寻常小球藻最大生物量与培养基中手动添加的初始FA浓度呈负相关，这表明培养基中积累的FA可能是主要的寻常小球藻生长抑制因子。FAs对寻常念珠菌的抑制作用主要是通过影响细胞的光合作用效率破坏细胞内的抗氧化剂系统来实现的。