Daping Li

Effect of organic carbon on nitrification efficiency and community composition of nitrifying biofilms.

The effects of organic carbon/inorganic nitrogen (C/N) ratio on the nitrification processes and the community shifts of nitrifying biofilms were investigated by kinetic comparison and denaturing gradient gel electrophoresis (DGGE) analysis. The results showed that the nitrification rate decreased with an increasing organic concentration. However, the effect became weak when the carbon concentration reached a sufficiently high level. Denitrification was detected after organic carbon was added. The 12 h ammonium removal rate ranged from 85% to 30% at C/N = 0.5, 1, 2, 4, 8, and 16, as compared to the control (C/N = 0). The loss of nitrogen after 24 h at C/N = 0.5, 1, 2, 4, 8, and 16 was 31%, 18%, 24%, 65%, 59%, and 62%, respectively. The sequence analysis of 16S rRNA gene fragments revealed that the dominant populations changed from nitrifying bacteria (Nitrosomonas europaea and Nitrobacter sp.) to denitrifying bacteria (Pseudomonas sp., Acidovorax sp. and Comamonas sp.) with an increasing C/N ratio. Although at high C/N ratio the denitrifying bacteria were the dominant populations, nitrifying bacteria grew simultaneously. Consequently, nitrification process coexisted with denitrification.

Reduction of Ti(IV) and Synthesis of Titanium Nanoparticles by Pseudomonas sp.MBR

The characteristics and influence factors of the reduction of complexes TiF62-to titanium were investigated by Pseudomonas sp.MBR with organic carbon source as electron donor in the presence of oxygen.The results indicated that the initial concentration of TiF62-could be 0.5~8.0 mmol/L,the optimum pH was 7.0,and citrate was the best carbon source.Furthermore,the best reduction effect was obtained when the molar ratio of the electron donor to TiF62-was 100 : 1.The results of scanning electron micrograph and transmission electron micrograph showed that the morphology of cells supplied with TiF62-had no remarkable difference compared to blank control,and the titanium nanoparticles distributed around the plasma membrane.

Mechanism and Characteristics of Electricity Generation in Microbial Fuel Cells Catalyzed by Mixed Culture

Dual-chamber microbial fuel cells(MFCs) were constructed by inoculating anaerobic sludge.The extracellular electron transfer mechanism of mixed bacteria in MFC anode chamber,the utilization of substrates and cathodic electron acceptors were investigated.The results showed that the mixed bacteria formed thick biofilm on carbon felt anode to facilitate the electron transfer between organic matter and MFC anode.Additionally,the MFC was capable of using a wide variety of organic compounds as electron donors for power generation,including monosaccharide,disaccharide as well as several types of small molecular organic fatty acid and ethanol.While sucrose and lactose as electron donors,the maximum power densities of the MFCs reached 69.69 mW/m2and 60.75 mW/m2,respectively.The highest COD loading of 123.55 mg L-1d-1was attained with ethanol as electron donor.Acidic permanganate as the cathodic electron acceptor could greatly increase power production with the maximum power density of 1 396.74 mW/m2.

Identi fication and Herbivory Characteristics of Naegleria sp. TH8

A protozoan TH8,which can graze Anabaena flos-aquae,was isolated from the water samples of the Taihu Lake.It was identified as Naegleria sp.through morphology and ITS rRNA sequence analysis.Under microscopy,the amoeba TH8 was slug-like,burst forward with a transparent hemispherical single pseudopodia,and had three forms of active feeding,dormant cyst and transient flagellate.TH8 grew well under condition from 10 ℃ to 30 ℃ preying the fresh A.flos-aquae,but not at 37 ℃ or in autoclaved A.flos-aquae.The growth rate of TH8 in exponential phase could reach 1.68 cell d-1 at 25 ℃.Moreover,TH8 showed better prey effect in exponential initial stage,later stage and stationary phase of A.flos-aquae than in exponential medium-term.Initial concentration of the amoeba TH8 had significant influence on elimination of A.flos-aquae.