Study On Flocculation Of Nostoc Sphaeroids

As a kind of microalgae with economic and nutritional value,Nostoc sphaeroids has received extensive attention,and factoryized mass production.There are many studies on the nutrition of Nostoc sphaeroids,but there are no reports on its flocculation activity research.This study will focus on the flocculation activity,flocculation mechanism and application of the substance after homogenization of Nostoc sphaeroids.The experiment mainly used kaolin and Microcystis aeruginosa 7806 as the treatment object,and tested whether Nostoc sphaeroids homogenate has flocculation activity,then,the effects of treatment time,concentration of Nostoc sphaeroids,temperature,pH value,types of coagulant and its addition amount on flocculation activity of Nostoc sphaeroids were determined.Next,the distribution of extracellular flocculating substances of Nostoc sphaeroids and its extraction method were studied,at the same time,the methods of polysaccharide and protein content detection methods,UV-visible spectrum scanning and high performance liquid chromatography were used to analyze the flocculant composition.Then the flocculation mechanism of Nostoc sphaeroids was explored.The effects of flocculation of Nostoc sphaeroids homogenate on the physiological activities of Microcystis cells and the flocculation effect on different microalgae were studied by scanning electron microscopy,chlorophyll fluorescence detection and microcystin content determination.Finally,the flocculation of the flocculant of Nostoc sphaeroids in natural water and the application experiment of the recovery of culture solution in the large-scale culture of Nostoc sphaeroids were carried out.The experimental results and analysis showed that Nostoc sphaeroids has a certain flocculating activity,under the promotion of calcium chloride,the flocculation of Nostoc sphaeroids has been significantly improved.The flocculating activity of Nostoc sphaeroids was greatly affected by the coagulant,followed by the treatment time and its own concentration,the higher temperature and the specific pH also have certain effects.The water-soluble polysaccharide and protein content after ethanol extraction were detected by centrifugal separation,and the water-soluble polysaccharide content was as high as 92.9%.Ultraviolet-visible spectroscopy revealed that the floc didn't contained nucleic,high performance liquid chromatography detection concluded that the flocculant contained water-soluble polysaccharides and protein absorption peaks,and no other absorption peaks were found.By detecting the binding amount of Ca²⁺in the flocculation system solution,it was found that the flocculation characteristics of Nostoc sphaeroids mainly acted by Ca²⁺bridge adsorption.The flocculation effect of Nostoc sphaeroids on microalgae showed that the flocculation effect of Nostoc sphaeroids on Anabaena 7120 and Microcystis aerugin 7806 was better,and the flocculation rate was 81.1%and 56.7%,the flocculation of Nostoc sphaeroids didn't affect the photosynthesis of the algae cells in a short time.The microcystins detection and scanning electron microscopy observations showed that the integrity of the cell structure was not destroyed.The flocculation of Nostoc sphaeroids has a certain ability to remove TN,ammonia nitrogen,TP and turbidity in natural water.Through the research on flocculation of Nostoc sphaeroids,it provides a new idea for the recovery and utilization of waste liquid in the large-scale cultivation of Nostoc sphaeroids.