Stimulation of Wheat Straw Biochar on the Roxarsone Biodegradation by Shewanella Oneidensis MR-1

Biochar-mediated microbial degradation is receiving increased attention for remediating organic pollutants. However, the mechanism of biochar-facilitated bioremediation is poorly understood. This study demonstrated that wheat straw biochar could significantly enhance roxarsone biodegradation by Shewanella oneidensis MR-1. The average rate constants were calculated to be 0.0410, 0.0477, 0.0575, and 0.0441 h⁻¹ for treatments with 0.05, 0.1, 0.5, and 1 g/L biochar, respectively, which were all higher than that in treatment with only MR-1 (0.0363 h⁻¹). The impact of biochar dosage on roxarsone degradation followed as 0.5 g/L > 0.1 g/L > 1.0 g/L > 0.05 g/L biochar. The high specific surface area of biochar provided more opportunity for contact with MR-1, which was certified by the scanning electron microscope images. The extracellular polymeric substances were affected by the addition of biochar. The concentrations of protein and polysaccharide were lower with various concentrations of biochar to the system with only MR-1. The cell proliferation was promoted by the addition of biochar and the optical density value of MR-1 followed 0.5 g/L biochar group > 0.1 g/L biochar group > 1 g/L biochar group > 0.05 g/L biochar group > only MR-1. These results improved our understanding of biochar-mediated biodegradation and showed that an optimized dosage of wheat straw-derived biochar could be a microbial growth activator, accelerating the roxarsone conversion rate.