The effect and mechanism of molybdenum electron shuttle on perchlorate bioreduction

Here, the enhancement effect and mechanism of MoO3 and silicomolybdic acid (SiMo12) on perchlorate bioreduction were investigated. The bioreduction rates of perchlorate at 36 h were enhanced 1.92 and 1.33-fold by SiMo12 and MoO3. According to electrochemical tests, SiMo12 and MoO3 improved the electrochemical activity and reduced the resistance, demonstrating that the electron transfer was accelerated. The secretion of intracellular cytochrome c (Cyt-c) was increased by 1.64-fold in SiMo12 replenished system, while was not increased in MoO3 replenished system. In addition, the secretion of membrane Cyt-c was increased by 2.05 and 1.58-fold in SiMo12 replenished system and MoO3 replenished system. The secretion of extracellular polymeric substance was enhanced 1.72-fold by SiMo12, while it was not enhanced by MoO3. The perchlorate reductase A (PcrA) in perchlorate reductase (Pcr) was promoted 1.41 and 1.21-fold by SiMo12 and MoO3. The mRNA reverse expression levels of perchlorate reductase O (PcrO) and perchlorate reductase Q (PcrQ) were increased by SiMo12, while were not affected by MoO3. This work provided a reliable strategy for accelerating the perchlorate reductase in wastewater bio-treatment.