Seawater Microbial Flocculant

J. Hao, Y. Zhang, J. Wang, B. Yang, T. Jiang, X. Zhang, A. Zhang, X. Zhang


Seawater has been used in many fields just like seawater desalination, seawater urban utilization and so on. The quality of seawater decides the efficiency of seawater utilization. Flocculants are commonly used to separate suspended solids portion from seawater. Over the past decades, many kinds of flocculants have been developed. Inorganic flocculants and organic synthetic flocculants are the most representative agents. But their use has caused some healthy and environmental problems. In this case, bioflocculant, which was characteristic of safety, is expected to develop. Our department has been committed to looking for special flocculants for seawater treatment. Recently, we focused our work on microbial flocculants. Microbial flocculants are produced by microorganisms or their secretions. We isolated three bacteria: Bacillus amyloliquefaciens dhs-28, Bacillus licheniformis dhs-36, Bacillus licheniformis dhs-40 and two fungi: Penicillium purpurogenum EL-02, Aspergillus niger ETYB-13 from the Bohai Gulf, Tianjin. They all showed high flocculating activity (flocculating rate>75%) toward seawater. Ammonium sulfate precipitation and ethanol precipitation were used to isolate flocculating active substances from fermentation supernatants. Freeze-vacuum dry formed powder at last. Chemical qualitative analysis, Ultraviolet (UV) spectrometry and Fourier-transform infrared (FTIR) spectrometry were used to decide properties of microbial flocculants. The main ingredients of flocculants from bacteria were proteins while the main ingredients of flocculants from fungi were polysaccharides. Depends on their properties, fungal flocculants showed better stability than bacterial flocculants in changes of temperatures and pH values. Viscosity method and gel permeation chromatography (GPC) showed the molecular weight of flocculants were above 10Da. These results suggested microbial flocculants derived from fungi were better than microbial flocculants derived from bacteria. Our lab is intended to transform microbial flocculants to products in future. We believe the microbial flocculants will play an important role in seawater treatment.

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American Society for Microbiology General Meeting
    • ASM 113th (2013)