Oxygen exposure deprives antimonate-reducing capability of a methane fed biofilm

This work is aiming at achieving antimonate (Sb(V)) bio-reduction in a methane (CH₄) based membrane biofilm reactor (MBfR), and elucidating the effect of oxygen (O₂) on the performance of the biofilm. Scanning electron microscope (SEM), energy dispersive X-ray (EDS) and X-ray photoelectron spectroscopy (XPS) confirm Sb₂O₃ precipitates were the main product formed from Sb(V) reduction in the CH₄-fed biofilm. Illumina sequencing shows Thermomonas may be responsible for Sb(V) reduction. Moreover, we found 8 mg/L of O₂ in the influent irreversibly inhibited Sb(V) reduction. Metagenomic prediction by Reconstruction of Unobserved State (PICRUSt) shows that the biofilm lacked efficient defense system to the oxidative stress, leading to the great suppress of key biological metabolisms such as TCA cycle, glycolysis and DNA replication, as well as potential Sb(V) reductases, by O₂. However, methanotrophs Methylomonas and Methylosinus were enriched in the biofilm with O₂ intrusion, in accordance with the enhanced abundance of genes encoding aerobic CH₄ oxidation. These insights evoke the theoretical guidance of microbial remediation using CH₄ as the electron donor towards Sb(V) contamination, and will give us a strong reference with regard to wastewater disposal.