Isolation and Identification of Flocclant-Producing Strain and Research its Flocculation Characteristics

To isolate an efficient flocculant-producing strain from sludge of piggery sewage sedimentation tank and investigate its flocculating properties of a bioflocculant produced.[Methods] Primary screening was done by using diluted plate count and selective medium, and secondary screening was carried out by flocculating rate of cell free fermentation broth supernatant flocculation 4g/L kaolin clay suspension. A cation-independent bioflocculant produced by strain FY-6 was isolated from sludge of piggery sewage sedimentation tank. Cell free fermentation broth supernatant was used as crude bioflocculant. Effects of impact factors (dosages, cations and pH) were investigated on the flocculation activity of the fermentation broth supernatant.[Results] Strain FY-6 was identified as Bacillus licheniformis based on 16S rDNA gene sequences. Both excessive and low fermentation broth supernatant doses resulted in low flocculating rates. The highest flocculating rate of 94.6% was recorded with 0.05% dosages of fermentation broth supernatant. The bioflocculant was cation-independent, as the addition of monovalent cations such as K⁺ and Na⁺ and divalent cations such as Mg²⁺, Ca²⁺ and Fe²⁺ could not enhance the flocculating rate, whereas the Fe³⁺ inhibited flocculation. Initially the flocculating activity increased with increases in pH at acidic conditions, attaining a maximum flocculating activity (94.2%) at neutral pH followed by a drop at alkaline pH conditions.[Conclusion] A cation-independent bioflocculant bacteria with a high flocculation was screened. It can be used as original strain to produce bioflocculant, because of its high rate of flocculation and add less of concentration.

Keywords:microorganism, flocculant, fermentation broth supernatant *Supported by the Key Projects of Spark Program of National (2014GA710002)  *Corresponding author. E-mail: llm56@ahau.edu.cn