Ministry of Education Key Laboratory of Pollution Control and Ecological Remediation for Industrial Agglomeration Area, School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China.
Ministry of Education Key Laboratory of Pollution Control and Ecological Remediation for Industrial Agglomeration Area, School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China.
Water Res. 2021 Feb 1;189:116612. doi: 10.1016/j.watres.2020.116612. Epub 2020 Nov 6.
The slow electron transfer rate is the bottleneck to the biological wastewater treatment process, and the nanoparticles (NPs) has been verified as a feasible strategy to improve the biological degradation efficiency by accelerating the electron transfer. Here, we employed the Gram-positive Bacillus megaterium Y-4, capable of synthetizing Pd(0), to investigate the intra/extracellular electron transfer (IET/EET) mechanisms mediated by NPs in aerobic denitrification for the first time. Kinetic and thermodynamic results showed that the bio-Pd(0) could significantly promote the removal of both nitrate and nitrite by improving affinity and decreasing activation energy. The enzymic activity and the respiration chain inhibition experiment indicated that the bio-Pd(0) could facilitate the nitrate biotic reduction by improving the Fe-S center activity and serving as parallel H carriers to replace coenzyme Q to selectively increase the electron flux toward nitrate in IET, while promoting the nitrite reduction by abiotic catalysis. Most importantly, the detection of DPV peak at -226~-287 mV proved that the one-electron EET via multiheme cytochrome-bound flavins also occurred in Gram-positive bacteria and enhanced in Pd-loaded cells. In addition, the remarkable increase of the formal charge in EPS indicated that the bio-Pd(0) could act as an electron shuttle to increase the redox site in EPS, eventually accelerating the electron hopping in long-distance electron transfer. Overall, this study expanded our understanding of the roles of bio-Pd(0) on the aerobic denitrification process and provided an insight into the IET/EET of Gram-positive strains.
电子转移速率缓慢是生物废水处理过程的瓶颈，而纳米颗粒 (NPs) 已被验证为通过加速电子转移来提高生物降解效率的可行策略。在这里，我们首次利用能够合成 Pd(0) 的革兰氏阳性菌 Bacillus megaterium Y-4 来研究 NPs 在好氧反硝化中介导的细胞内/外电子转移 (IET/EET) 机制。动力学和热力学结果表明，生物 Pd(0) 可以通过提高亲和力和降低活化能来显著促进硝酸盐和亚硝酸盐的去除。酶活性和呼吸链抑制实验表明，生物 Pd(0) 可以通过提高 Fe-S 中心活性并作为平行 H 载体替代辅酶 Q 来选择性增加 IET 中硝酸盐的电子流，从而促进硝酸盐的生物还原，同时通过非生物催化促进亚硝酸盐的还原。最重要的是，在 -226~-287 mV 处检测到 DPV 峰证明了通过多血红素细胞色素结合黄素的单电子 EET 也发生在革兰氏阳性菌中，并在负载 Pd 的细胞中增强。此外，EPS 中形式电荷的显著增加表明，生物 Pd(0) 可以作为电子穿梭体来增加 EPS 中的氧化还原位点，最终加速长距离电子转移中的电子跳跃。总的来说，这项研究扩展了我们对生物 Pd(0) 在好氧反硝化过程中的作用的理解，并深入了解了革兰氏阳性菌的 IET/EET。
