| Exopolysaccharides (EPS) were secreted into environment by somemicroorganisms in the process of growth and metabolism. They were watersolubleand could be get from the fermentation broth easily. EPS belonged to secondarymetabolite products which were natural and synthetic polymers. Some EPS werenontoxic and possessed the properties similar to plant polysaccharides and syntheticpolymer materials. EPS are widely used in food industry, water treatment, medicineand so on. EPS were renewable resources which could be produced in industry byfermentation. In addition, the production and quality of EPS were not influenced byregions and weather conditions.In this paper, strain CY-7was isolated from activated sludge in Jinan everbrightwater Co., LTD and was identified as Klebsiella sp by physiological and biochemicalassay and16S rDNA BLAST. CY-7could produce mass adhesiveness EPS. In orderto develop and utilize EPS from Klebsiella sp. CY-7better, a large number ofexperiments were investigated, including fermentation production, components,constructions, physicochemical property and applications in water treatment.The fermentation of CY-7was influenced by several parameters such asnutritional components of culture medium, fermentation temperature and ventilationvolume. Single Factor Experiment indicated that the optimal carbon source andnitrogen source were sucrose and KNO3respectively. Through Response SurfaceMethods, the optimum medium consisted sucrose31.93g/L, KNO32.17g/L, K2HPO45.47g/L, NaCl0.1g/L, KH2PO42.0g/L,(NH4)2SO40.2g/L, MgSO4·7H2O0.2g/L.Using the optimal medium, Klebsiellac CY-7was cultivated for80h and theproduction of exopolysaccharides was up to13.38g/L, which was increased18.2%than unoptimization. The optimal conditions included temperature, inoculumsconcentration, seed age, outfit fluid amount, rotate speed, initial pH and fermentationtime were28.9℃,10.6%,13h,50mL,200rpm, pH7.0and80h, respetively. Aftercultivating for80h with the optimal conditions, the maximal production of EPS was 15.06g/L,10.4%higher than unoptimization.After the fermentation of Klebsiella sp. CY-7strain, crude extracellularpolysaccharides(HZ-7) was then obtained by precipitating in ethanol. HZ-7wastreated by sevag and was purified by gel permeation chromatography (SephacrylS-500). and then its physical and chemical properties was thoroughly analyzed.that.HZ-L consisted of91.49%total sugar and41.67%uronic acid. The molecularweight was about194KDa, which was determined by the method of Multi-anglelaser light scattering. The fourier transform infrared spectroscopy showed thepresence of the absorbance peak around3425cm-1which reflected-OH stretchingvibration, and the absorbance peak around2920cm-1which reflected C-H stretchingvibration, and the absorbance peak around1724cm-1and1616cm-1which reflectedC=O stretching vibration, and the absorbance peak around1053cm-1whichreflected C-O stretching vibration.HZ-7could be used as bioflocculant and applied to treat the dyingwastewater and water from Yellow River, and the flocculating ability was94.67%and93.72%separately. The adsorption performance of HZ-7on Cr (VI) and theeffect of the adsorption time, pH and temperature on the adsorption were studied. Theinitial pH was important for biosorption, and the optimum effect on Cr (VI)biosorption was acquired within initial pH0.5-1.0. HZ-7had excellent effect ondealing with wastewater that has low concentration of Cr (VI). The removal rate of Cr(VI) could reach to95%when the total concentrations of Cr (VI) were10.0-50.0mg/L.The results of static test showed that the adsorption equilibrium was reached after80minutes. The absorbance peak around3417cm-1moved about5cm-1, and itsabsorbance strength decreased. Similarly, the absorbance peak around2918cm-1decreased. The absorbance peak around1643cm-1moved about6cm-1, and itsabsorbance decreased too. |
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