Wen Qin

Ammonium removal by a novel oligotrophic Acinetobacter sp. Y16 capable of heterotrophic nitrification-aerobic denitrification at low temperature.

Ammonium removal from source water is usually inhibited by insufficient carbon sources and low temperature in Northeastern China. A strain Y16 was isolated from oligotrophic niche and was identified as Acinetobacter sp. Y16. It demonstrated excellent capability for ammonium removal at 2 °C, and simultaneously produced nitrogen gas as the end product. About 66% of ammonium was removed after 36 h of incubation. Only trace accumulation of nitrate was observed during the process. The utilization of nitrite and nitrate as well as the existence of napA gene further proved the aerobic denitrification ability of strain Y16. Sodium acetate was the most favorable carbon source for ammonium oxidation by strain Y16. High rotation speed was beneficial for ammonium oxidation. Furthermore, strain Y16 could efficiently remove ammonium at low C/N ratio and low temperature conditions, which was advantageous for nitrogen removal from source water under cold temperatures.

Removal of ammonium in surface water at low temperature by a newly isolated Microbacterium sp. strain SFA13.

The strain SFA13, isolated from Songhua River, demonstrates ability to convert ammonium to nitrogen under aerobic conditions at low temperature. On the basis of 16S rRNA gene sequence, the strain SFA13 was a species in genera Microbacterium. The isolate showed unusual ability of autotrophic nitrification with the ratio of 0.11 mg NH4(+)-N/L/h at 5°C. Ammonium was consumed by the strain SFA13 with the biodegradation of organic carbon and without nitrite or nitrate accumulation. NO3(-)-N or NO2(-)-N was reduced by the strain SFA13. The denitrification ratio was 0.24mgNO3(-)-N/L/h. Hydroxylamine oxidase, nitrite reductase and nitrate reductase were detectable. The putative nitrogen removal process by the strain SFA13 was as follows: NH4(+)→NH2OH→NO2(-)→NO3(-), then NO3(-)→NO2(-)→N2. Biological activated carbon attached with the strain SFA13 could effectively remove ammonium in surface water with the rate of 2.68±0.27-3.16±0.25 mg NH4(+)-N/L/h at C/N 2-10, temperature 10°C, and DO>5.2 mg/L.

Acinetobacter harbinensis sp. nov., isolated from river water.

A bacterial strain, HITLi 7T, with nitrifying ability was isolated from the surface water of the Songhua River in China. Cells were Gram-stain-negative, strictly aerobic, oxidase-negative, non-motile coccobacilli, capable of growth in mineral media with acetate as the sole carbon source and ammonia as the sole source of nitrogen. The cells did not grow at 37 °C, but did grow at 2 °C. The DNA G+C content was 45.5 mol%. Results of 16S rRNA gene sequence analysis indicated a close relationship between this isolate and Acinetobacter lwoffii (98.4% similarity for strain DSM 2403T). rpoB and gyrB gene sequences did not show significant similarity with those from other species of the genus Acinetobacter. Predominant cellular fatty acids were 9-octadecenoic acid (C18 : 1ω9c) and summed feature 4 (iso-C15:0 2-OH and/or C16:1ω7c). Acid was not produced from d-glucose, and gelatin was not hydrolysed by the isolate. Genotypic, phenotypic and chemotaxonomic data from this study indicate that the isolate should be classified as a representative of a novel species of the genus Acinetobacter. The name Acinetobacter harbinensis sp. nov. is proposed for the novel species, with HITLi 7T (=CGMCC 1.12528T=KCTC 32411T) as the type strain.

Microbial community composition and function in a pilot-scale anaerobic-anoxic-aerobic combined process for the treatment of traditional Chinese medicine wastewater

Biodegradation of traditional Chinese medicine (TCM) wastewater was investigated in a pilot-scale anaerobic-anoxic-aerobic combined process, which was composed of an expanded granular sludge blanket (EGSB) reactor, a hydrolysis acidification (HA) reactor and a biological contact oxidation (BCO) reactor. In stable stage, the average values of COD and color in the combined process effluent were 45.7mgL-1 and 13 times, respectively. Excellent linear relations (R2>0.915) were achieved between color and UV254 at three color levels. Comprehensive community structures of the combined process were analysed by Illumina MiSeq Sequencing, which revealed that microbial community in the aerobic reactor had the greatest diversity and richness. Bacteroidetes, Firmicutes and Proteobacteria were dominant phyla in the three reactors, and Bacteroidales, Geobacter, ZB2 were the predominant functional microorganisms in the anaerobic, anoxic and aerobic reactors, respectively. Good removal efficiencies and presence of core microorganisms confirmed that the combined process was feasible for treating TCM wastewater.

Purification and characterization of a low-temperature ammonia monooxygenase from heterotrophic nitrifier Acinetobacter sp. Y16

AbstractLow-temperature ammonia monooxygenase (AMO) was purified from a heterotrophic nitrifier Acinetobacter sp. Y16 by anion-exchange and gel-filtration chromatography. The purified enzyme was a membrane-bound monomer with a molecular mass of approximately 31 kDa. It could catalyze the oxidation of ammonium without stabilizing agents in vitro at low temperature. Addition of CuCl2 could stimulate AMO activity in vitro. The enzyme was stable in the temperature range of 4–15°C with less than 9% change in its activity. The optimal activity temperature was 15°C. Above 20°C, the enzyme completely lost its activity. The enzyme activity was stable when stored at 4°C for five days, at 10°C for two days, and at 15°C for one day. This study purified a highly pure AMO from a heterotrophic nitrifier Acinetobacter sp. for the first time.

Purification and Characterization of a Low-temperature Hydroxylamine Oxidase from Heterotrophic Nitrifier Acinetobacter sp. Y16

OBJECTIVE To purify a low-temperature hydroxylamine oxidase (HAO) from a heterotrophic nitrifying bacterium Acinetobacter sp. Y16 and investigate the enzyme property. METHODS A HAO was purified by an anion-exchange and gel-filtration chromatography from strain Y16. The purity and molecular mass were determined by RP-HPLC and SDS-PAGE. The HAO activity was detected by monitoring the reduction of potassium ferricyanide using hydroxylamine as substrate and ferricyanide as electron acceptor. The partial amino acid sequence was determined by mass spectrometry. RESULTS The low-temperature HAO with a molecular mass of 61 kDa was purified from strain Y16 by an anion-exchange and gel-filtration chromatography. The enzyme exhibited an ability to oxidize hydroxylamine in wide temperature range (4-40 °C) in vitro using hydroxylamine as substrate and ferricyanide as electron acceptor. It was stable in the temperature range of 4 to 15 °C and pH range of 6.0 to 8.5 with less than 30% change in its activity. The optimal temperature and pH were 15 °C and 7.5, respectively. Three peptides were determined by mass spectrometry which were shown to be not identical to other reported HAOs. CONCLUSION This is the first study to purify a low-temperature HAO from a heterotrophic nitrifier Acinetobacter sp. It differs from other reported HAOs in molecular mass and enzyme properties. The findings of the present study have suggested that the strain Y16 passes through a hydroxylamine-oxidizing process catalyzed by a low-temperature HAO for ammonium removal.

Substrates removal and growth kinetic characteristics of a heterotrophic nitrifying-aerobic denitrifying bacterium, Acinetobacter harbinensis HITLi7 T at 2 °C

In order to investigate the heterotrophic nitrification and aerobic denitrification ability of Acinetobacter harbinensis HITLi7T at 2 °C, both the growth parameters and substrates utilization characteristics were tested and appropriated kinetic models were obtained in this study. Under the initial concentration of 5 mg/L, the maximum NH4+-N and NO3--N degradation rates were 0.076 mg NH4+-N/L/h and 0.029 mg NO3--N/L/h, respectively. At the simultaneous presence of 2.5 mg/L NH4+-N and NO3--N, the maximum nitrate removal rate increased to 0.054 mg NO3--N/L/h (1.86 folds), while a slight decrease was observed in NH4+-N removal. Two double-substrate models, Contois-Contois (1) for NH4+-N and TOC, Monod-Contois (2) for NO3--N and TOC matched well with the experimental data. The kinetic parameters were determined as μmax1 = 0.095 h-1, BA1 = 0.012 mg/L, BT1 = 0.784 g TOC/g biomass (R12 = 0.9997), and μmax2 = 0.032 h-1, KN2 = 0.375 mg/L, BT2 = 1.108 g TOC/g biomass (R22 = 0.9731) by multiple regression equation.

Draft Genome Sequences of Acinetobacter harbinensis Strain HITLi 7T, Isolated from River Water

Acinetobacter harbinensis HITLi strain 7(T), isolated from river water, has the ability to remove ammonium and organic chemicals at 2°C. The genome sequences might be useful for investigating the low-temperature adaptability and nitrogen or organic chemical metabolism.

Isolation, Identification and Characterization of Heterotrophic Nitrifying Bacteria from Surface Water

For reducing ammonium concentration and guaranteeing safe drinking water, three heterotrophic bacteria were isolated from the Songhua River, which were SFA6, SFA7 and SFA11. When the initial ammonium concentration was about 130 mg/L, the ammonium removal rate of the strains SFA7, SFA6 and SFA 11 were 1.54 mg NH4+/L/h, 1.20 mg NH4+/L/h and 1.27 mg NH4+/L/h respectively at 8 °C. The 16S rDNA sequence results revealed that the strain SFA6 was Bacillus subtilis, SFA7 was Pseudomonas putida, and SFA11 showed similarity to Pseudomonas nitroreducens. The biochemical characteristics of SFA6 were quite different from that of SFA7 and SFA11. After 48 h degradation, the NH4+-N (about 5 mg/L) was consumed to 0.23±0.15 mg/L, 0.37±0.20 mg/Land 0.58±0.17 mg/L by the strains SFA6, SFA7 and SFA11, with little NO3--N and NO2--N accumulation. Above all, the strains SFA6, SFA7 and SFA11 could be used in drinking water treatment at 8 °C. The strain SFA6 showed the highest ammonium removal efficiency.

Impact of ozonation and biologically enhanced activated carbon filtration on the composition of micropollutants in drinking water

A pilot-scale drinking water treatment process for Songhua River, including conventional treatment (coagulation-settlement and rapid sand filtration), ozonation, biological enhanced activated carbon (BEAC) filtration, and chlorination disinfection, was carried out in this study. To investigate the impact of ozonation and BEAC filtration on removing the composition of micropollutants in drinking water, we detected the micropollutant composition from each stage of the treatment process by non-targeted analysis using a GC-MS technique and compared the results between effluents of single BEAC and O3-BEAC processes. Aromatic compounds and esters could be abated efficiently during single BEAC filtration via biodegradation and adsorption; however, possible metabolic products (i.e., alkenes) were formed by biodegradation. Comparatively, O3-BEAC process could reduce micropollutants much more significantly than single BEAC process especially for aromatic compounds including substituted benzenes and polycyclic aromatic hydrocarbons (PAHs) without the formation of metabolic products through the coupling effect of oxidation, biodegradation, and adsorption, suggesting that ozonation improved the removal potential of micropollutants in the BEAC process. In addition, conventional and novel chlorinated disinfection by-products were also measured during post-chlorination.