A compound bioflocculant CBF,produced by mixed culture of Rhizobium radiobacter F2 and Bacillus sphaeicus F6, was investigated with regard to its production and flocculating properties. The optimization of the culture medium constituents including carbon source,nitrogen source and C / N ratio,metal ions and ionic strength on CBF production were studied. Flocculating properties of CBF were examined by a series of experiments and CBF had good flocculating activities in kaolin suspension with divalent cations and stable over wide range of p H. Studies of the flocculating properties revealed that the flocculation could be stimulated by cations Ca2+,Mg2+,Fe2+,Al3+and Fe3+. In addition,it was stable at 4-30 ℃ in the presence of Ca Cl2. It was found to be effective for flocculation of a kaolin suspension under neutral and weak alkaline conditions( p H 7. 0- 9. 0),and flocculating activities of higher than 95% were obtained when the CBF concentrations among 6- 14 mg / L at p H 8. 0. The results of this study indicate that CBF is a potential replacement of conventional synthetic flocculants and is widely applied in water treatment and downstream processing of food and fermentation industries.
为实现低温生物甲烷高效转化与发酵系统稳定运行,应探索提高低温沼气发酵细菌代谢能力途径与冷适机制。研究以发酵温度(10、15、18、22、25°C和30°C)为驱动因子,人工培养基定向富集自然低温生境混合菌群,考察沼气发酵细菌低温生物甲烷转化效能,并耦合454高通量测序和PCR-DGGE解析低温混合菌群落结构。结果表明,低温生境混合细菌最优势细菌类群为Clostridium XI sp.,占细菌总数的40.9%,确定分类地位的产甲烷菌有Methanosaeta sp.和Methanobacterium sp.。低温沼气发酵细菌在18°C富集培养的沼气产量最高,可达220 ml L^(-1)reactor d^(-1),甲烷含量为56.8%。
