Effects of Sulfamethoxazole on the Microbial Community Dynamics During the Anaerobic Digestion Process.

Valentina Mazzurco Miritana,Antonella Signorini,Andrea Visca,Luisa Patrolecco,Silvia Rosa,Jasmin Rauseo,Gian Luigi Garbini,Francesca Spataro,Giulia Massini,Paola Grenni,Anna Barra Caracciolo

doi:10.3389/fmicb.2020.537783

Abstract

Anaerobic digestion (AD) treatment of cattle manure and slurry makes it possible to produce biogas, a renewable and storable biofuel, as well as digestate, a residual organic matter that can be used to replace chemical fertilizers. On the other hand, the intense use of antibiotics (e.g., sulfamethoxazole) in animal husbandry practices is showing increasing negative impacts resulting from the release of still metabolically active molecules into agroecosystems. In the present study, cattle manure collected from an AD plant-feeding tank was used as feedstock for AD experiments in which some batches were spiked with 5 mg L–1 of sulfamethoxazole (SMX). Adding the antibiotic affected the microbial community dynamic; in particular, the efficiency of the acidogenic and acetogenic phases of the process corresponded to higher CH4 and H2 production than in the control. SMX was also degraded, and at the end of the experiment (69 days), just 20% of its initial concentration was found. The relative abundance (ARG/16S) of resistance genes sul1, sul2, and the proxy intI1 initially found in the ingestate decreased during the AD in both the spiked and control batches, suggesting that this process lowers the likelihood of antibiotic resistance genes spreading.

Highlights

Anaerobic digestion (AD) is an efficient process that transforms organic waste, e.g., agriculture and breeding residues, into renewable energy and digestate (Guo et al, 2015; Sui et al, 2017; European Biogas Association, 2018; Styles et al, 2018)
The results show a selective effect of SMX on the microbial community, which did not hamper AD, and stimulated some microbial populations involved in biogas production and in the antibiotic degradation
The AD process promoted an overall lowering of the antibiotic resistance genes (ARGs) load inside the microbial community in both control and SMX conditions

Summary

Introduction

Anaerobic digestion (AD) is an efficient process that transforms organic waste, e.g., agriculture and breeding residues, into renewable energy (biogas) and digestate (Guo et al, 2015; Sui et al, 2017; European Biogas Association, 2018; Styles et al, 2018). The latter, containing considerable amounts of plant-essential macro- and micro-nutrients, is a good alternative to chemical fertilizers (Bustamante et al, 2012; Barra Caracciolo et al, 2015; Bharathiraja et al, 2018). The environmentally friendly application of digestate on agricultural soil does not exclude the likelihood of introducing antibiotics, such as sulfamethoxazole (SMX); the latter is commonly used in livestock production worldwide (Rauseo et al, 2019)

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Results

Conclusion