Biochar-Mediated Degradation of Roxarsone by Shewanella oneidensis MR-1.

Li Wengang,Chen Fang,Chen Cuihong,Zhong Rong

doi:10.3389/fmicb.2022.846228

Abstract

It is widely believed that biochar plays an essential role in sequestrating pollutants. The impacts of biochar on microbial growth, and consequently on the environmental fate of pollutants, however, remains poorly understood. In this study, wheat-straw-derived biochar was used to investigate how biochar amendment affected Shewanella oneidensis MR-1 growth and roxarsone transformation in water under anaerobic conditions. Three biochar with different physicochemical properties were used to mediate the roxarsone degradation. The results showed that the degradation rate of roxarsone could be accelerated by the increase of biochar pyrolysis temperature. From the characterization of biochar, the total specific surface area, micropore surface area and micropore volume of biochar increase, but the average pore diameter decreases as the pyrolysis temperature increases. Through infrared spectroscopy analysis, it was found that as the pyrolysis temperature increases, the degree of condensation of biochar increases, thereby increasing the pollutant removal rate. From the changes of the relative concentration of MR-1 and its secreted extracellular polymer content, the growth promotion ability of biochar also increases as the pyrolysis temperature increases. These results suggest that wheat-straw-derived biochar may be an important agent for activating microbial growth and can be used to accelerate the transformation of roxarsone, which could be a novel strategy for roxarsone remediation.

Highlights

As human demand for meat continues to increase, the poultry industry has gradually become one of the fastest-growing agricultural sectors in decades
The ability of biochar to promote the degradation of roxarsone by MR-1 was followed as: 600BC > 500BC > 300BC
It was found that the change of ln(C0/Ct) with time (t) showed a good linear relationship (C0 is the initial concentration of roxarsone, Ct is the concentration of roxarsone remaining in the reaction when the reaction time is t), in line with the first-order kinetic reaction fitting equation

Summary

Introduction

As human demand for meat continues to increase, the poultry industry has gradually become one of the fastest-growing agricultural sectors in decades. Through the extensive application of veterinary drugs and feed additives, production efficiency and product quality have been improved (Sarmah et al, 2006). Roxarsone (3-nitro-4-hydroxyphenylarsine) was first produced 70 years ago, which was used as feed additives to control coccidial intestinal parasites and prevent parasitic infections and improve the pigmentation of meat (Silbergeld and Nachman, 2008; Nachman et al, 2013). The use of roxarsone in the poultry industry has been banned in most developed countries, including China, but long-term extensive usage has resulted in a massive accumulation of roxarsone in the environment (Huang et al, 2019; Wang G. et al, 2020). Along with the storage or field application of animal waste or direct discharge into the environment, roxarsone can enter into the surfaceor ground-water and soil due to its water-soluble capacity (Silbergeld and Nachman, 2008; Huang et al, 2019). Roxarsone can be oxidized, reduced, methylated or demethylated through numerous physical, chemical and biological interactions, and eventually produce a variety of arsenic compounds (Garbarino et al, 2003; Chen et al, 2016; Han et al, 2017; Oyewumi and Schreiber, 2017)

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Results