Efficient recycling of Spirulina platensis culture medium and identification of its growth inhibitors
Spirulina platensis(S.platensis)and its derivative products,have garnered considerable attention in the realms of food and biomedicine due to their high nutritional content.However,during the cultivation of S.platensis,copious amounts of water are required for both cell growth and nutrient suspension,leading to high water usage,increased costs,extensive nutrient waste,and substantial growth inhibition during the recycling process.This study aimed to assess the effectiveness of treating culture solution of S.platensis using four methods(0.45 μm filter membrane,10 kDa ultrafiltration membrane,macroporous resin S-8,and activated carbon),evaluate the changes of growth and nutrient compositions of S.platensis after five recycles of culture solution,and identify the characteristics of extracellular inhibition and its constituents.The results showed that the circulation culture of Spirulina could greatly reduce the water consumption and culture cost,and improve the yield and quality of Spirulina.The culture solution pretreatment of S.platensis could effectively reduce the inhibition effect of extracellular organic matter,the negative effects can be effectively reduced,so that there was almost no difference between the microalgae obtained from the reused medium and the fresh medium and the order of treatment effects were 10 kDa ultrafiltration membrane＞macroporous resin S-8＞activated carbon＞0.45 µm filter membrane.After five recycles of culture solution,the cell weight of S.platensis in the 10 kDa ultrafiltration membrane treatment group decreased only 5.9％,and that of the 0.45 µm filter membrane treatment group significantly decreased about 22％(p＜0.05),but its intracellular polysaccharide content increased 217％due to the coercive effect of cell metabolism.In addition,the extracellular inhibitors in the culture solution were mainly extracellular polysaccharide,consisting of monosaccharides such as fucose(19.98％),rhamnose(15.61％),and glucose(14.75％).Therefore,this research holds significant implications for enabling sustainable,large-scale spirulina cultivation via the recycling of spirulina culture fluid.In addition,it contributes to nutrient accumulation,cost reduction,and decreased usage of nutrient salts.
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