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To determine the potential effects of seasonal changes on water temperature and water quality upon removal of ammonium and organic carbon pollutants and to characterize the variations in microbial characteristics, a pilot-scale activated carbon filter biologically enhanced with heterotrophic nitrifying bacteria was investigated for 528 days. The results show that 69.2 ± 28.6% of ammonium and 23.1 ± 11.6% of the dissolved organic carbon were removed by the biologically enhanced activated carbon (BEAC) reactor. It is shown that higher biodegradable dissolved organic carbon enhances ammonium removal, even at low temperatures. The C/N ratio consumed by the BEAC reactor reached a steady value (i.e., 3.3) after 2 months of operation. Despite seasonal fluctuations and competition of the indigenous community, the heterotrophic nitrifying bacteria (Acinetobacter sp. HRBLi 16 and Acinetobacter harbinensis strain HITLi 7) remained relatively stable. The amount of carbon source was the most significant environmental parameter and dramatically affected the microbial community compositions in the BEAC reactor. The present study provides new insights into the application of a BEAC reactor for ammonium removal from drinking water, resisting strong seasonal changes.

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., (Copyright © 2014 The Editorial Board of Biomedical and Environmental Sciences. Published by China CDC. All rights reserved.)

We sought to confirm whether use of Acinetobacter strains Y7 and Y16, both strains of heterotrophic nitrifying bacteria, was practical for removing ammonium (NH-N) from drinking water at low temperatures. To test this, ammonium-containing drinking water was treated with strains Y7 and Y16 at 8 and 2 °C. Continuous ammonium treatment was conducted in order to evaluate the performance of three biologically enhanced activated carbon (BEAC) filters in removing ammonium. The three BEAC filters were inoculated with strain Y7, strain Y16, and a mixture of strains Y7 and Y16, respectively. A granular activated carbon (GAC) filter, without inoculation by any strains, was tested in parallel with the BEAC filters as control. The results indicated that NH-N removal was significant when a BEAC filter was inoculated with the mixture of strains Y7 and Y16 (BEAC-III filter). Amounts of 0.44 ± 0.05 and 0.25 ± 0.05 mg L NH-N were removed using the BEAC-III filter at 8 and 2 °C, respectively. These values were 2.8-4.0-fold higher than the values of ammonium removal acquired using the GAC filter. The synergistic effect of using strains Y7 and Y16 in concert was the cause of the high-ammonium removal efficiency achieved by using the BEAC-III filter at low temperatures. In addition, a high C/N ratio may promote NH-N removal efficiency by improving biomass and microbial activity. This study provides new insight into the use of biofilters to achieve biological removal of ammonium at low temperature. [ABSTRACT FROM AUTHOR]

Acinetobacter sp. HITLi 7 T showed capacity of heterotrophic nitrification at 2 °C with an optimum growth temperature of 20 °C. The ammonium removal rates were 0.09 and 0.24 mg l −1 h −1 at 2 °C and 20 °C respectively. Cell growth and proliferation affected ammonium removal performance of HITLi 7 T dramatically at low temperature. To investigate the influence of low temperature on protein expression, the response of HITLi 7 T cultivated at 2 °C and 20 °C were characterized and compared by 2-dimensional proteome analyses. A total of 151 proteins were identified to be differentially expressed by the analysis of PDQuest 2D gel analysis software. In comparison to protein expression at 20 °C, 17, 28, and 43 protein spots were found to be up-regulated, down-regulated and only present at 2 °C, respectively. 9 spots, which were overexpressed or induced at low temperature, were successfully identified by peptide mass fingerprinting by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry. The significantly up-regulated proteins at 2 °C were related to metabolism. The proteins only present at 2 °C had functions of protein biosynthesis and refolding. These findings indicated that cold adaption of HITLi 7 T relied on regulation of metabolic pathways, synthesis of proteins and protein refolding. [ABSTRACT FROM AUTHOR]