Inhibition mechanism and biological recycling utilization of microalgae culture aging solution

During the process of recovering microalgae culture media, the culture media will age and inhibit the growth of microalgae. When the culture media was reused for the third time, the maximum biomass of Spirulina platensis FACHB-439 was only 56.13% of the fresh culture media. But the inhibitors in the aging solution are not known. In this study, the growth inhibition mechanism of Spirulina platensis aging solution was clarified through the identification of target organic matter by cyclic culture experiment and ion chromatography. The results showed that the growth inhibitors in the aging solution were polysaccharides, mainly including fucose and rhamnose. Further reverse addition experiments confirmed that polysaccharide inhibitors would increase with the increase of repeated use of the culture media. By inhibiting the synthesis of photosynthetic pigments in microalgae, they could cause oxidative damage and membrane peroxidation of microalgae cells, resulting in stress on the growth of microalgae. At the same time, this study established a purification method for reusing aging solution of heterologous microalgae (Chlorella sp. L166) to obtain high lipid and high carbohydrate biomass energy. The results showed that the biomass of Chlorella sp. L166 in the first circulating aging solution of S.platensis FACHB439 increased by 25%, the carbon utilization rate reached 21.36%, the lipid content per cell increased by 1.61 times, and the carbohydrate content increased by 86.71%. This work is helpful to solve the problem that aging of culture media inhibits carbon sequestration efficiency and biomass yield of microalgae in large-scale production of microalgae. And the results of this study have achieved high utilization rate of water resource for large-scale cultivation of microalgae, which is conducive to realize the scale development of microalgae biotechnology.