Microbial reduction of antimony under anaerobic conditions by inocula from different sources

Antimony (Sb) is a toxic and carcinogenic metalloid that can be present in contaminated water generated by mining operations and other industrial activities. Dissimilatory Sb(V) reduction to Sb(III) under anaerobic conditions by prokaryotic microbial communities has been reported; however, the fate of antimony in anaerobic wastewater treatment systems is poorly understood. This study investigated the potential of six different inoculum sources to reduce Sb(V) under anaerobic conditions and correlated the Sb(V) reduction rate with the microbial community composition. Microbial reduction of Sb(V) to Sb(III) by all the inoculum sources tested was observed in anaerobic incubations using hydrogen as an electron donor after a month. The highest reduction rate observed was 12.5 mg Sb per gram of volatile suspended solids per day. In some inocula, not only Sb reduction was observed, but also a decrease in the total Sb concentration, suggesting the precipitation of Sb(III). Metagenomic analysis revealed high variability in the community diversity associated with the origin of the inoculum. For the family taxonomic category, the three inocula that showed the highest Sb reduction potential were characterized by the presence of the Bacillaceae family.