Abstract
A salt-tolerant denitrifying bacterium F1 was isolated in this study, which has high nitrite (NO2−–N) and nitrate (NO3−–N) removal abilities. The salt tolerance capacity of strain F1 was further verified and the effects of initial pH, initial NaNO2 concentration and inoculation size on the denitrification capacity of strain F1 under saline conditions were evaluated. Strain F1 was identified as Pannonibacter phragmitetus and named Pannonibacter phragmitetus F1. This strain can tolerate NaCl concentrations up to 70 g/L, and its most efficient denitrification capacity was observed at NaCl concentrations of 0–10 g/L. Under non-saline condition, the removal percentages of NO2−–N and NO3−–N by strain Pannonibacter phragmitetus F1 at pH of 10 and inoculation size of 5% were 100% and 83%, respectively, after cultivation for 5 days. Gas generation was observed during the cultivation, indicating that an efficient denitrification performance was achieved. When pH was 10 and the inoculation size was 5%, both the highest removal percentages of NO2−–N (99%) and NO3−–N (95%) by strain Pannonibacter phragmitetus F1 were observed at NaCl concentration of 10 g/L. When the NaCl concentration was 10 g/L, strain Pannonibacter phragmitetus F1 can adapt to a wide range of neutral and alkaline environments (pH of 7–10) and is highly tolerant of NaNO2 concentration (0.4–1.6 g/L). In conclusion, strain Pannonibacter phragmitetus F1 has a great potential to be applied in the treatment of saline wastewater containing high nitrogen concentrations, e.g. coastal aquaculture wastewater.
Highlights
Due to the advantages of a short production cycle, high yield and convenient management, coastal aquaculture has rapidly developed as a pillar industry in the coastal region of China (Liang et al 2018)
A heterotrophic denitrifying bacterium Pannonibacter phragmitetus B1 was isolated from aquaculture water, which had denitrifying genes nirK, norB and narG (Bai et al 2019)
The salt tolerance of strain Pannonibacter phragmitetus F1 was verified after confirming its denitrification capacity, which fills both the knowledge and technical gaps of application in saline conditions
Summary
Due to the advantages of a short production cycle, high yield and convenient management, coastal aquaculture has rapidly developed as a pillar industry in the coastal region of China (Liang et al 2018). Owing to lack of indispensable production management and pollution control, more than 60% of the nitrogen in feed for coastal aquaculture was discharged into the adjacent waters without sufficient treatment, resulting in severe. Nitrogen removal by microorganisms mainly uses bacteria (e.g. nitrifying bacteria, denitrifying bacteria, etc.) with nitration and denitrification capacities to achieve morphological transformation of various nitrogenous compounds in wastewater (Lv et al 2017). The nitrification of nitrifying bacteria can effectively remove N O2−–N from water, it cannot thoroughly solve the nitrogen pollution problem, as nitrate is the final product of microbial nitrification and the denitrification of N O3−–N is still needed. In a high saline environment, the growth and metabolism of most bacteria are likely to be inhibited, and even lead to death. To identify bacteria with both denitrification capacity and salt tolerant characteristic is of great practical significance
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