Effects of carbon sources and operation modes on the performances of aerobic denitrification process and its microbial community shifts.

Carbon source, operation mode and microbial species have great effects on the synthesis of poly-ß-hydroxybutyrate (PHB) which has been identified as the key issue for aerobic denitrification process. In this study, an aerobic denitrification SBR was operated under anoxic/oxic mode and completely oxic mode with the carbon source of CH3COONa and CH3CH2CH2COONa, respectively. Total nitrogen (TN) removal efficiencies, PHB content in activated sludge, production of nitric oxide (NO) and nitrous oxide (N2O) of the process were investigated in great detail. The main results obtained from the trial were: (1) the average TN removal was in the range of 86.11%-90.05%; (2) the maximum TN removal efficiency and the maximum PHB content of the process being achieved when the carbon source of CH3CH2CH2COONa was applied under anoxic/oxic mode; (3) in case of CH3COONa as the carbon source, the concentrations of NO and N2O in the bulk liquid were ∼0.4 mg/L and ∼0.02 mg/L, respectively, while in case of CH3CH2CH2COONa, N2O of ∼0.2 mg/L and NO of ∼2.5 mg/L were recorded and the latter was decreased to ∼1.0 mg/L at the end of the cycle; (4) no obvious dominant genus in case of using CH3COONa, while Plasticicumulans sp. being the major microbial community when using CH3CH2CH2COONa. Overall, the effect of carbon source on microbial community is obvious. Nevertheless, operation mode affects the PHB synthesis, while PHB plays an important role in aerobic denitrification process for achieving a relatively high TN nitrogen removal efficiency. CH3COONa is a better carbon source for aerobic denitrification compared with CH3CH2CH2COONa.

Biocompatibility of defect-related luminescent nanostructured and microstructured hydroxyapatite.

Three defect-related luminescent hydroxyapatite (HAP) particles, S1, S2, and S3, with different morphologies (the samples S1 and S2 are nanorods with diameters of 25 nm and lengths of 30 and 100 nm, respectively; sample S3 is bur-like microspheres with diameters of 5-6 µm) were synthesized, and their biocompatibility was investigated by MTT, reactive oxygen species (ROS), interleukin-6 (IL-6), comet, and hemolysis assays. The results indicated that all samples were stable in cell culture medium and did not induce the synthesis of proinflammatory cytokine IL-6 or result in hemolysis. It was found that samples S1 and S3 inhibited osteoblast (OB) viability at concentrations of 5, 10, 20, 40, and 80 µg/mL for 24, 48, and 72 h. Sample S2 had no effect on the viability of OB at all tested concentrations for 24 and 48 h, but the viability of OB was increased at concentrations of 20, 40, and 80 µg/mL for 72 h. Samples S1 and S3 could increase the level of cellular ROS; sample S2 had no effect on the level of cellular ROS at a concentration of 20 µg/mL for 48 h. Although samples S1 and S3 induced significant DNA damage, sample S2 could not cause significant DNA damage at a concentration of 20 µg/mL for 72 h. The results suggest that longer nanorod HAP can show excellent biocompatibility and therefore may find potential applications in biomedical fields.