Bioelectrochemistry ( IF 5 ) Pub Date : 2020-08-25 , DOI: 10.1016/j.bioelechem.2020.107637 Rita Vieira Lemos 1 , Seiya Tsujimura 2 , Pablo Ledezma 1 , Yoshihide Tokunou 3 , Akihiro Okamoto 4 , Stefano Freguia 5
Extracellular electron transfer (EET) by the cyanobacterium Microcystis aeruginosa was investigated. Observations indicate that EET onto an electrode poised at + 0.6 vs. standard hydrogen electrode (SHE) is triggered by high pH, more evidently at pH levels above 9. Light intensity does not appear to affect electricity generation, indicating that this may not be a “biophotovoltaic” process. The generated current density was amplified with stepwise pH increases from approximately 5 mA m−2 at pH 7.8 to 30 mA m−2 at pH 10.5, for dense (0.4 mg mL−1 dry weight) Microcystis aeruginosa suspensions with dissolved CO2 and O2 approaching equilibrium with atmospheric concentrations. The upsurge in current density was more pronounced (from 5 mA m−2 at pH 7.8 to 40 mA m−2 at pH 10.2) in the absence of the cells’ natural electron acceptors, dissolved CO2 and O2. However, the latter effect is more likely due to competition for electrons by oxygen than to reductive stress. EET in this species is therefore a light-independent process that is enhanced by increasing pH, with reasons that are still unknown, but either related to the involvement of protons in the last step of electron transfer, or to intracellular pH control.
中文翻译:
铜绿微囊藻的细胞外电子转移完全由高pH驱动。
研究了铜绿微囊藻的胞外电子转移(EET)。观察结果表明,高pH值会触发EET到达与标准氢电极(SHE)相比处于+ 0.6的电极上,更明显的是在pH值高于9时触发。光强度似乎不会影响发电,表明这可能不是因为“生物光伏”过程。对于稠密(0.4 mg mL -1干重)的铜绿微囊藻悬浮液,具有溶解的CO 2和O,随着pH的逐步增加,pH从7.8的约5 mA m -2增加到pH 10.5的30 mA m -2,产生的电流密度被放大。2与大气浓度接近平衡。在没有细胞的天然电子受体,溶解的CO 2和O 2的情况下,电流密度的升高更加明显(从pH 7.8的5 mA m -2到pH 10.2的40 mA m -2)。但是,后一种效应更可能是由于氧对电子的竞争,而不是归因于还原应力。因此,该物种中的EET是一种与光无关的过程,该过程可以通过增加pH来增强,其原因尚不清楚,但原因可能与质子参与电子转移的最后一步有关,或者与细胞内pH控制有关。