Sunlight-triggered synergy of hematite and Shewanella oneidensis MR-1 in Cr(VI) removal
Sunlight-triggered synergy of hematite and Shewanella oneidensis MR-1 in Cr(VI) removal
复制标题
DOI：
10.1016/j.gca.2021.04.034
复制
发表时间：
2021-05-20
影响因子：
5
通讯作者：
Liu, Juan
中科院分区：
文献类型：
--
作者：
Cheng, Hang;Jing, Zehua;Liu, Juan
赤铁矿通常被认为是异化金属还原细菌（DMRB）的终端电子受体，如希瓦氏菌MR-1。然而，赤铁矿也是一种具有可见光响应的半导体。赤铁矿的光催化活性如何影响其与DMRB的电相互作用，以及其在阳光下相关生物地球化学过程中的作用尚不清楚。在这项研究中，我们采用了批处理实验和光化学分析，研究了赤铁矿在黑暗和阳光下对赤铁矿MR-1去除Cr（VI）的影响，并在一个由赤铁矿MR-1覆盖的太阳能辅助微生物光化学系统中进行了研究。在暗色条件下，低矿细胞比的赤铁矿可以通过吸附赤铁矿表面/附近的Cr（VI）和细菌来促进Cr（VI）的去除，有利于Cr（VI）的生物还原，同时也缓解了细胞随时间的自中毒过程。然而，当矿物与细胞比达到较高水平时，赤铁矿颗粒可能覆盖细胞表面，影响Cr（VI）的生物还原，导致Cr（VI）去除率随着赤铁矿颗粒的增加而降低。在模拟阳光下，S. oneidensis MR-1通过乳酸代谢产生电子，并利用这些电子填充赤铁矿中的光激空穴，产生光激电子来还原Cr（VI）。因此，除了直接酶促还原Cr（VI）外，新的光触发电子转移途径乳酸-> S. oneidensis MR-1 ->赤铁矿-> Cr（VI）进一步促进了Cr（VI）的去除和乳酸代谢。此外，模拟阳光下赤铁矿的存在增加了时间依赖性细胞存活率，这可能是由于促进了赤铁矿表面Cr（VI）的还原和Cr（III）产物的积累。此外，有机空穴清除剂乙二胺四乙酸（EDTA）可进一步增强赤铁矿和S. oneidensis MR-1在光照射下对Cr（VI）的去除。光化学结果证实，在光照作用下，光触发的电子传递途径可以迅速而重复地产生，而Cr（VI）尖峰后光电流的快速下降表明赤铁矿光电子对Cr（VI）进行了还原。这些发现表明，半导体矿物，如赤铁矿，可以收集太阳能，促进微生物代谢和非光养、电活性细菌的污染物转化，这反过来又增加了细菌对周围环境中有毒化合物的耐受性。(C) 2021 Elsevier Ltd版权所有。
Hematite is usually considered as a terminal electron acceptor for dissimilatory metal-reducing bacteria (DMRB), such as Shewanella oneidensis MR-1. However, hematite is also a semiconductor with visible light response. How the photocatalytic activity of hematite affects its electrical interplay with DMRB, as well as its role in relevant biogeochemical processes under sunlight, is still unclear. In this study, we investigated the effect of hematite on Cr(VI) removal by S. oneidensis MR-1 in the dark versus under stimulated sunlight using both batch experiments and photoelectrochemical analysis in a solar-assisted microbial photoelectrochemical system with a hematite photoanode covered by S. oneidensis MR-1. Under the dark conditions, hematite at low mineral-to-cell ratios can promote Cr(VI) removal through adsorbing both Cr(VI) and bacteria on/near hematite surface, which facilitates Cr(VI) bio-reduction and also alleviates self-poisoning processes of cells with time. However, as mineral-to-cell ratios reach a high level, hematite particles may cover cell surface and impact Cr(VI) bio-reduction, leading to the decreased Cr(VI) removal with increasing hematite particles. Under simulated sunlight, S. oneidensis MR-1 generates electrons from lactate metabolism and utilizes them to fill photoexcited holes in hematite, generating photoexcited electrons to reduce Cr(VI). Thus, in addition to directly enzymatic reduction of Cr(VI), the new light-triggered electron transfer pathway: lactate -> S. oneidensis MR-1 -> hematite -> Cr(VI) further increases Cr(VI) removal and lactate metabolism. Also, the time-dependent cell survival is increased by the presence of hematite under the simulated sunlight, probably owing to the promoted Cr(VI) reduction and accumulation of Cr(III)-products on hematite surface. Moreover, organic hole scavenger, such as Ethylenediaminetetraacetic acid (EDTA), can further enhance Cr(VI) removal by hematite and S. oneidensis MR-1 under light irradiation. The photoelectrochemical results confirm that the light-triggered electron transfer pathway can be promptly and repeatedly produced upon illumination, and the rapid decrease of photocurrents after spiking Cr(VI) indicates Cr(VI) reduction by the photogenerated electrons from hematite. These findings suggest that semiconducting minerals, like hematite, can harvest solar energy to boost microbial metabolism and contaminant transformation by non-phototrophic, electroactive bacteria, which in turn increases bacterial tolerance toward toxic compounds in surrounding environments. (C) 2021 Elsevier Ltd. All rights reserved.