Studying Of The Structure Characterization And Incubation Condition Optimization Of Bioflocculant Production By Klebsiella Sp. NIII2

Bioflocculant are new solid liquid separation agents, which are the secondarymetabolites secreted by microorganisms, mainly of polysaccharides, glycoproteins, proteins,nucleic acids, etc. It should be used in many aeras, such as wastewater treatment，beverageindustry, bio pharmaceuticals and so on. However，high production costs and low yield haslimited its use to more widely aeras. Therefore，it has important practical and theoreticalsignificance to flocculant development to study the ways of improving bioflocculant yield andflocculating activities, as well as the structure and composition of flocculant and factorsinfluenting its activities。Based on much abundant research of this project group, this paper has optimized thefermentation conditions of bioflocculant production by Klebsiella sp. NIII2. Besides thecharacteristics of secretion of flocculant by Klebsiella sp. NIII2，the influences of carbonsource, nitrogen source, Magnesium ion and their dosage on the structure of flocculant byKlebsiella sp. NIII2were studied. Meanwhile, the connection mode between glucide andpeptone of bioflocculant by Klebsiella sp. NIII2was researched. The major research results asfollows:（1） The composition of optimized medium of flocculant secreted by Klebsiella sp. NIII2is: Sucrose20g/L, distilled water1000mL,Urea0.75g/L, MgSO₄12mg/L, Phosphate buffersolution （as PO34P）685mg/L, and a certain quantity of microelement. When the initialconditions of the medium was pH7, temperature was30℃，rotary shaking speed was150r/min, inoculability quantity was6%,fermentation60hours, the highest bioflocculantyield was5.0g/L. It was normal phenomenon that the color of fermentation liquor turned fromcolorless to yellow. Corresponding with the color trends, the pH value changed around6.5.（2） The bioflocculant extract secreted by Klebsiella sp. NIII2was white powder, its solubility in water being8¹0g/L, pH in the range of6.8⁷.5under natural dissolved state,zeta potential being80⁵0mv. When the extract was heated2hours under temperature100℃, its activities had little change. So the extract possessed certain heat stability.Carbonsource, nitrogen source in the fermentation could influence the composition and structure ofthe bioflocculant secreted by Klebsiella sp. NIII2. Bioflocculant secreted by Klebsiella sp.NIII2contained glucide，protein and nucleic acid three kinds of materials. When Urea asnitrogen source and Sucrose as carbon source，adding an appropriate amount of magnesiumions made protein content in bioflocculant increased.（3） Bioflocculant secreted by Klebsiella sp. NIII2contained functional groups, such asCOOH，NH₂，OH and C O C. When nitrogen source was different，the zeta potential of thebioflocculant had significant differences, for example，when sodium nitrate being nitrogensource, the zeta potential value was negative. The amount of magnesium ions had noinfluence on the composition of bioflocculant. However, with the adding amount increased，the protein content in the bioflocculant and its activities also increased. This bioflocculant hadbuffering effect on acid and alkali. Once the buffering range was exceeded, as pH valuegreater than11or less than4, the zeta potential sharply increased with the adding of acid oralkali.（4） When Sucrose as carbon source,urea, sodium nitrate, ammonium chloride or peptoneas nitrogen source to secrete bioflocculant by Klebsiella sp. NIII2, the connection mode ofglucide and protein was O glycoprotein in the flocculant moleculars.While sucrose beingcarbon source and ammonium sulfate being nitrogen source, the connection mode wasN glycoprotein.The research work in this paper layed a foundation for the future pilot study ofbioflocculant secreted by Klebsiella sp. NIII2，Meanwhile, it was the in depth study basis ofbioflocculant structure and mechanism.