Structural Characterization And Activity Of Extracellular Polysaccharides From Flocculating Active Bacteria In The Adhesion Sludge Of Philippine Clam

Marine microorganisms can produce extracellular polysaccharides(EPS)with novel chemicals and unique biological activity due to the unique habitat environment.Thus,the study of marine microbial extracellular polysaccharides has become a research hotspot in recent years.In this study,three strains of bacteria with flocculating activity were isolated and extracted from the adhesion sludge of the Philippine clams.The pure exopolysaccharide of a single strain was obtained through fermentation technology,and a single polysaccharide component was obtained through concentration,dialysis,alcohol precipitation,and Sevage purification.All the isolated polysaccharide were?-pyranose,and the chemical composition and structure were further analyzed,and the flocculation decolorization and antioxidant activity were also evaluated.The main results were as follows:1.A single polysaccharide obtained from the fermentation broth of Psychrobacter sp.GHF10 had a molecular weight of 848000 Da,mainly composed of glucosamine,ribose,mannose,and glucose,with a ratio of 0.51:0.12:0.26:2.93,with-OH,C=O and CO and other functional groups.GC-MS analysis results showed that the glycosidic bond connection mode of the polysaccharide exists Manp 1?2?3?4 connection,Manp 1?4connection,end Manp connection,Glcp 1?4 connection,Glcp 1?4?6 connection,Glc NAcp end Connect to Glc NAcp 1?6 connection.The best flocculation rate was70.1%at the polysaccharide dosage of 0.6 mg L^-1for kaolin(4 g L^-1),and the best decolorization rate was 94.2%as polysaccharide concentration reached 2 mg L^-1.The EC₅₀of the half-maximal effective concentration of and·OH radicals were 0.23 mg L^-1and0.37 mg L^-1,respectively.2.A single polysaccharide extracted from the fermentation broth of Pseudoalteromonas sp.GHS5 had a molecular weight of 634000 Da,which was mainly composed of galactose,mannose,ribose,and glucosamine,with a ratio of 0.34:1:0.09:0.17.The analysis of the glycosidic bond connection mode showed that it had Galp 1?3connection,Manp 1?3 connection,Manp 1?6 connection,Manp 1?2?3?4 connection,Glc NAcp 1?3?4?6 connection,Rbip 1?2?3?4 connection and Rbip end connection and other connection methods.When the polysaccharide concentration was 0.6 mg L^-1and2 mg L^-1,the best flocculation rate and decolorization rate were 80.1%and 93.7%,respectively.The semi-maximal effect on DPPH·radicals and·OH free radicals were 0.35mg L^-1and 0.15 mg L^-1of the polysaccharide,respectively.3.A single polysaccharide extracted from the fermentation broth of Bacillus sp.GHS8-1 had a molecular weight of 166000 Da and composed of mannose,galactose,and glucosamine with a ratio of 0.46:2.3:0.3.There were Glc NAc 1?6 connection,Galp1?4?6 connection,Galp 1?3?4 connection,and Manp 1?6 connection in this single polysaccharide.The optimal flocculation rate and decolorization rate were 70.1%and94.2%as the polysaccharide concentration reached 0.8 mg L^-1and 1.5mg L^-1,respectively.This polysaccharide also had the half-maximal effective concentration for DPPH·radicals and·OH radicals at 0.24 mg L^-1and 0.35 mg L^-1,respectively.Hence,the isolated and purified polysaccharides of the three strains all had main functional groups such as hydroxyl,carbonyl,methylene,and carbon skeleton ring,but the molecular weight,monosaccharide composition and glycosidic bond had significant difference.In addition,polysaccharide from strain S5 had the best flocculation activity and hydroxyl radical scavenging activity,and polysaccharide from strain F10 had the best scavenging activity on DPPH radicals.