Study On The Flocculation Mechanism Of Bioflocculant From Ruditapes Philippinarum Conglutination Mud

Bioflocculants is a kind of nontoxic,harmless,biodegradable macromolecules which originated from bacterium,fungus and other microorganisms.Bioflocculants comprise extracellular polymeric substances such as polysaccharides,protein,glycoprotein,lipid and other complex chemical components.It's popularly applied in the water treatment,food fermentation and other industrial fields.Ruditapes philippinarum,also named as clam,is one of the four cultivated shellfish in China and abundantly distributed in China coastal areas.Where there is the clam residing,the water above tends to be clear.To figure out this phenomenon,we made efforts in the following area:(1)Extraction of active materialPolysaccharides from the conglutination mud was extracted through hot water method.In single experiment trial,extraction time,extraction temperature,water to solid ratio and number of extraction times were discussed.The results showed the former three variable affected the polysaccharide yield greatly.Through the operation of Design Expert8.0.6.1(trial),the optimum extraction conditions were confirmed as followed: extraction time,4.07h;extraction temperature,91.59?;ratio of water to solid,20.07mL/g.Under theses parameters,as for 5Kg fresh clam,116.57±1.19 mg polysaccharides was extracted from the conglutination mud,which was quite close to the model estimated value122.45 mg.(2)Purification and characterization of active materialThe water extracted exopolymer was precipitated by absolute alcohol,deprotained by Sevag reagent(trichloromethane:n-butyl alcohol=4:1,v/v),UV Spectroscopy Scan was used to ensure the associated proteinous substances were absolutely eliminated.Then the crude RPMP(Ruditapes philippinarum conglutination mud polysaccharide)was sequentially purified by a anion-exchange chromatography column DEAE-52 and a Sephadex G-100 gel permeation chromatography.The resultant two purified fractions RPMP-1 and RPMP-2 were lyophilized for further study.Chemical analysis showed that the main constituent of RPMP was 1.24%(w/w)protein with a bulk of 97.76%(w/w)polysaccharides.Fourier infrared absorption spectrum showed the existance of hydroxyl,carboxyl and carbonyl groups both in RPMP-1 and RPMP-2,which was favor for the flocculating process.The monosaccharide compositionof RPMP-1 and RPMP-2 was analyzed by HPLC(Agilent 1260).The results indicated that both RPMP-1 and RPMP-2 comprised mannose,glucosamine,rhamnose,glucuronic acid,galacturonic acid,galactosamine,glucose,galactose,xylose,arabinose,fucose.The average molecular weight of of RPMP-1 and RPMP-2 were 5.7KDa and 18 KDa respectively measured by GPC.(3)Flocculating effect of active materialThe flocculating efficiency of the originated mud,RPMP,RPMP-1 and RPMP-2were determined respectively.The outcome suggested that the originated mud had the highest flocculating rate of 91.79%±2.18% in the seawater kaolin suspension and86.69%±2.13% in the freshwater kaolin suspension respectively at the dosage 8g/L.And the performance of turbidity removal for the other three declined.However,proper dosage proportions of RPMP-1 and RPMP-2 would enhance the flocculating performance.When adding concentration reached 180?g/L of RPMP-1 and 80?g/L of RPMP-2 simultaneously,the flocculating activity ascended to 65.58±1.64%.(4)Ecological composition of Ruditapes philippinarum conglutination mudFour ecological factors including bacterium,fungus,sterile clam,residing sediment were investigated to ascertain the key role in the flocculating system.The spitting mud of each group was proceeded by MiSeq sequencing analysis to determine the richness and diversity of microorganism.Polysaccharides secreted by bacterium(MBF)was confirmed to be the main active substance for the flocculating effect while fungus and sterile clam had trivial influence.Both the organic components(MBF)and inorganic components(sand)contributed for the excellent performance of RPMP bioflocculants.