Dissimilatory and Cytoplasmic Antimonate Reductions in a Hydrogen-Based Membrane Biofilm Reactor

Abstract

A hydrogen-based membrane biofilm reactor (H2-MBfR) was operated to investigate the bioreduction of antimonate [Sb­(V)] in terms of Sb­(V) removal, the fate of Sb, and the pathways of reduction metabolism. The MBfR achieved up to 80% Sb­(V) removal and an Sb­(V) removal flux of 0.55 g/m2·day. Sb­(V) was reduced to Sb­(III), which mainly formed Sb2O3 precipitates in the biofilm matrix, although some Sb­(III) was retained intracellularly. High Sb­(V) loading caused stress that deteriorated performance that was not recovered when the high Sb­(V) loading was removed. The biofilm community consisted of DSbRB (dissimilatory Sb-reduction bacteria), SbRB (Sb-resistant bacteria), and DIRB (dissimilatory iron-reducing bacteria). Dissimilatory antimonate reduction, mediated by the respiratory arsenate reductase ArrAB, was the main reduction route, but respiratory reduction coexisted with cytoplasmic Sb­(V)-reduction mediated by arsenate reductase ArsC. Increasing Sb­(V) loading caused stress that led to increases in the expression of arsC gene and intracellular accumulation of Sb­(III). By illuminating the roles of the dissimilatory and cytoplasmic Sb­(V) reduction mechanism in the biofilms of the H2-MBfR, this study reveals that the Sb­(V) loading should be controlled to avoid stress that deteriorates Sb­(V) reduction.

Electrodeposited Palladium Nanoparticles Enhancing Atomic Hydrogen-Mediated Electrochemical Recovery of Antimony

“…Meanwhile, the peak separation analysis indicated that the extracted Sb species comprised a blend of trivalent and zerovalent states, primarily existing as metal oxide (Figure S11c). ,− Therefore, a logical conclusion can be drawn that the electroreduction products resulting from the Sb­(III) solution constitute a composite of Sb 0 and Sb 2 O 3 .…”

Biogenic Palladium Improved Perchlorate Reduction during Nitrate Co-Reduction by Diverting Electron Flow in a Hydrogenotrophic Biofilm

“…Operated in parallel were two identical MBfRs, shown in Figure S1 and similar to our previous studies. 22,23 Each MBfR comprised a main column containing a 32-fiber bundle and a sampling column containing a 20-fiber coupon bundle for biofilm sampling. The fibers were nonporous polypropylene hollow fibers (Teijin, Japan), which supplied bubble-free H 2 on-demand H 2 to the biofilm attached to the exterior surface.…”

It Is Time to Explore Unique Mechanisms for Microbial Antimony Conversion Rather Than Relying on Analogies with Arsenic Bioconversion

“…Recent studies have shown that Sb(V) could also upregulate the expression of the arsC gene, leading to the hypothesis that microbes reduce Sb(V) intracellularly through the As reductase enzyme ArsC and then further detoxify Sb(III) via ArsB. 4 However, the role of ArsC in Sb(V) reduction, at the gene or protein level, remains unverified.…”

“…Furthermore, both As­(III) and Sb­(III) could trigger As-based defense mechanisms in microbes, manifesting as the upregulated expression of ars gene clusters, facilitating the removal of As­(III) and Sb­(III) from the cells. Recent studies have shown that Sb­(V) could also upregulate the expression of the arsC gene, leading to the hypothesis that microbes reduce Sb­(V) intracellularly through the As reductase enzyme ArsC and then further detoxify Sb­(III) via ArsB . However, the role of ArsC in Sb­(V) reduction, at the gene or protein level, remains unverified.…”