| Paenibacillus elgii B69is capable of producing bioflocculants. Bioflocculants have been widely used in the field of wastewater treatment as water treatment agent due to their characteristics in efficient, cheap, ecofriendly, biodegradable and not harmful to the environment. Bioflocculants can overcome the inherent defect of traditional inorganic flocculants, organic synthetic flocculants in not thorough, not environmental and even not safe. Thus, the application of bioflocculants has a very important practical significance on human health and the environment protection. However, high cost, low yield and low activity remain key factors limiting the wide-scale application of flocculants. Therefore, it is specially important to select strains producing high activity bioflocculant and increase the production of bioflocculant. In this thesis, a study on optimization, purification and characterization of polysaccharide-based bioflocculant produced by Paenibadllus elgii B69was discussed. In addition, a series of experiments was performed to investigate the flocculation activities towards kaolin clay, dyeing pigment, heavy metal ion, and real wastewater. All of the research have laid the foundation of increasing the production, reducing the cost, and promoting the practical application of bioflocculant from P.elgii B69.The main contents of this thesis are as follows:1. Optimization of medium for producing bioflocculant by Paenibacillus elgii B69. Firstly, The classical one-factor-at-a-time method was used to evaluate two most important ingredients, carbon and nitrogen source, of the production medium, and sucrose and peptone were found to be the most effective C and N sources, respectively.Then, the effects of the ingredients in the production medium on bioflocculant production were analyse through Plackett-Burman design, steepest ascent experimental, central composite design and response surface methodology.The result showed that the maximum bioflocculant production was about25.64g/L achieved with sucrose at51.35g/L, peptone at6.79g/L and yeast extract at0.46g/L (keeping other ingredients at initial concentration). The concentration of carbon and nitrogen of the optimal condition were much lower than those of reported result in the similar study (188.2g/L and25.8g/L respectively), and the optimum yield was much higher than that of reported result in the similar study (3.44g/L).Thus, it not only greatly reduced the production cost but also improved the yield of the desired product.2. Study on the purification and characterization of the bioflocculant. The crude bioflocculant obtained was deproteinized through combining the enzyme with Sevag reagent, and then purified by Q Sepharose Fast Flow column chromatography. The physical and chemical properties of the purified sample were studied using a series of methods.The result revealed that the bioflocculant is a kind of exo-polysaccharides comprised of glucose, glucuronic acid, xylose, and mannose at a ratio of1.95:1:2.07:0.93, respectively, with a molecular weight of about3.5*106Da and a characteristic of high viscosity (7850cP).3. Study on the flocculating activities of the bioflocculant for removing pollutants from wastewater.In this thesis, the flocculation activities towards kaolin clay, dyeing pigment, heavy metal ion and real wastewater were investigated. The result showed that the bioflocculant could reduce up to87%turbidity of kaolin solution, and could efficiently remove dyeing pigment, heavy metal ion such as Al3+, Pb2+, Cu2+and Co2+,and even performed a satisfactory flocculating efficiency in the clarification of real wastewater. The decontamination of the flocculant was not only equal to other natural polymer flocculants and organic synthetic flocculants, but also had a variety of mixed pollutant removal performance.All the above results of efficient fermentation synthesis efficient, molecular properties, industrial wastewater pretreatment effects about the new bioflocculant showed its greater potential value. |
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