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. 2025 Jan 29;13(2):297.
doi: 10.3390/microorganisms13020297.

Characteristics and Mechanism of Ammonia Nitrogen Removal by Heterotrophic Nitrification Bacterium Klebsiella pneumoniae LCU1 and Its Application in Wastewater Treatment

Meng Xu  1   2 , Lifei Chen  1   2 , Yizhen Xin  1   2 , Xiangyu Wang  1 , Zhuoya Wang  1 , Xueqiang Meng  1 , Wenyu Zhang  1 , Haoyang Sun  1 , Yifan Li  1 , Wenzhe Zhang  1 , Peng Wan  1 , Bingshuai Geng  1 , Lusheng Li  1   2
Affiliations

Characteristics and Mechanism of Ammonia Nitrogen Removal by Heterotrophic Nitrification Bacterium Klebsiella pneumoniae LCU1 and Its Application in Wastewater Treatment

Meng Xu et al. Microorganisms. .

Abstract

In this study, a novel strain exhibiting heterotrophic nitrification was screened; subsequently, the strain was identified as Klebsiella pneumoniae LCU1 using 16S rRNA gene sequencing. The aim of the study was to investigate the effects of external factors on the NH4+-N removal efficiency of strain LCU1 in order to elucidate the optimal conditions for NH4+-N removal by the strain and improve the removal efficiency. The findings indicated that the NH4+-N removal efficiency of the strain exceeded 80% under optimal conditions (sodium succinate carbon source, C/N ratio of 10, initial pH of 8.0, temperature of 30 °C, and speed of 180 rpm). The genome analysis of strain LCU1 showed that key genes involved in nitrogen metabolism, including narGHI, nirB, nxrAB, and nasAB, were successfully annotated; hao and amo were absent, but the nitrogen properties analysis determined that the strain had a heterotrophic nitrification ability. After 120 h, the NH4+-N removal efficiency of strain LCU1 was 34.5% at a high NH4+-N concentration of 2000 mg/L. More importantly, the NH4+-N removal efficiency of this strain was above 34.13% at higher Cu2+, Mn2+, and Zn2+ ion concentrations. Furthermore, strain LCU1 had the highest NH4+-N removal efficiency of 34.51% for unsterilised (LCU1-OC) aquaculture wastewater. This suggests that with intensive colonisation treatment, the strain has promising application potential in real wastewater treatment.

Keywords: Klebsiella pneumoniae; heterotrophic nitrification; wastewater treatment.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Morphological observation of strain LCU1: (A) Gram staining of LCU1. (B) Scanning electron microscope image of LCU1. (C) The phylogenetic tree of LCU1 derived from neighbour-joining analysis of partial 16S rRNA sequences.
Figure 2
Figure 2
Growth and heterotrophic nitrification characteristics of strain LCU1.
Figure 3
Figure 3
Heterotrophic nitrification characteristics of strain LCU1 growth in (A) KNO3 and (B) NaNO2.
Figure 4
Figure 4
Effect of single factor on NH4+-N removal and cell growth of strain LCU1. OD600 value data were obtained after strain LCU1 had been cultured for 24 h: (A) carbon source, (B) C/N ratio, (C) temperature, (D) initial pH, (E) speed, (F) salinity, (G) heavy metals, and (H) initial high NH4+-N concentration.
Figure 5
Figure 5
Circular graphic visualisation of the distribution of strain LCU1 genome annotations. Genome wide circle mapping of LCU1 genome circle layers from inside to outside: genome size identifier, coding sequence and COG functional classification, rRNAs and tRNAs, GC content, and GC values.
Figure 6
Figure 6
The key genes of LCU1 in the nitrogen metabolism pathway were successfully annotated in the KEGG database (green signifies the denitrification pathway; purple denotes the nitrification pathway; orange represents the nitrogen fixation pathway; question marks are used to indicate that the relevant genes were not annotated).
Figure 7
Figure 7
NH4+-N removal efficiency of strain LCU1 treatment of perch aquaculture wastewater. (* indicates p value ≤ 0.05, *** indicates p value ≤ 0.001).
See this image and copyright information in PMC

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