High Resistance of a Sludge Enriched with Nitrogen-Fixing Bacteria to Ammonium Salts and Its Potential as a Biofertilizer.

Claudia Rodriguez-Gonzalez,Janeth Sanabria,Carolina Ospina-Betancourth

doi:10.3390/bioengineering8050055

Claudia Rodriguez-Gonzalez, Janeth Sanabria + Show 1 more

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https://doi.org/10.3390/bioengineering8050055

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Journal: Bioengineering	Publication Date: May 1, 2021
Citations: 4	License type: CC BY 4.0

Affiliation: University of Valle, Newcastle University

Abstract

The increasing use of chemical fertilizers causes the loss of natural biological nitrogen fixation in soils, water eutrophication and emits more than 300 Mton CO2 per year. It also limits the success of external bacterial inoculation in the soil. Nitrogen fixing bacteria can be inhibited by the presence of ammonia as its presence can inhibit biological nitrogen fixation. Two aerobic sludges from wastewater treatment plants (WWTP) were exposed to high ammonium salts concentrations (>450 mg L−1 and >2 dS m−1). Microbial analysis after treatment through 16S pyrosequencing showed the presence of Fluviicola sp. (17.70%), a genus of the Clostridiaceae family (11.17%), and Azospirillum sp. (10.42%), which were present at the beginning with lower abundance. Denaturing gradient gel electrophoresis (DGGE) analysis based on nifH genes did not show changes in the nitrogen-fixing population. Nitrogen-Fixing Bacteria (NFB) were identified and associated with other microorganisms involved in the nitrogen cycle, presumably for survival at extreme conditions. The potential use of aerobic sludges enriched with NFB is proposed as an alternative to chemical fertilizer as this bacteria could supplement nitrogen to the plant showing competitive results with chemical fertilization.

Highlights

Dinitrogen (N2 ) is one of the nutrients that limits and controls the productivity and functioning of agricultural ecosystems [1]
It is possible that the remaining 42.86% of bacterial species were not associated with the nitrogen cycle but we propose that they are related to the carbon cycle, for example, saccharose transformation via aerobic and anaerobic pathway
High ammonium salts (>50 mg L−1 ) concentrations did not affect in a negative way the presence of Nitrogen Fixing Bacteria population

Summary

Introduction

Dinitrogen (N2 ) is one of the nutrients that limits and controls the productivity and functioning of agricultural ecosystems [1]. There are two main ways to fix nitrogen: first, through human engineered processes (54%) such as a) the Haber–Bosch process (H–B); and b) fossil fuel combustion or in a bioreactor culturing specific strains of NitrogenFixing Bacteria (NFB). Nitrogen can be fixed by natural processes (46%); for example, oxidation of nitrogen by electric storms and biological fixation [2]. H–B and fossil fuel digestion processes are associated with negative environmental impacts because they cause more than 1.6% CO2 global emissions [4,5,6]. The use of fertilizers modifies the diversity of the soil microbial community [7], water eutrophication and toxicity [8]. Soil salinization reduces natural biological nitrogen fixation and crop productivity [8,9]

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