The aim of this study was to investigate pH effect on stratification of bacterial community in cathodic biofilm of the microbial fuel cell (MFC) under alkaline conditions. A single-chamber MFC with air-cathode was operated with 0.8 g/L maltodextrin and bicarbonate buffer solutions under pH values of 8.5, 9.5, and 10.5, respectively. The cathodic biofilms were characterized by linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), confocal laser scanning microscopy (CLSM), freezing microtome and high-throughput sequencing analysis on bacterial communities, respectively. Results showed that the maximum power densities in the MFC increased with the pH values and reached 1221 ± 96 mW/m² at pH = 10.5 during ∼30 d of operation. With different pH values, the composition and relative abundance of bacterial community significantly changed in the bottom (0 – 50 μm), middle (50 – 100 μm), and top (100 – 150 μm) layers of the cathodic biofilm. With pH = 10.5, aerobic bacteria accounted for 12%, 13%, and 34% of the bacterial community in the top, middle, and bottom layers, respectively. The amount of anaerobic bacteria in the top and middle layers (i.e., 52%, and 50% of the bacterial community, respectively) was higher than that in the bottom layer (22%). The distribution of aerobic and anaerobic bacteria showed a “valley-peak” structure within the layers. The high CO₃^2- concentration facilitates the hydroxyl transfer and the neutralization in the anode of the MFC under high alkali conditions. The results from this study should be useful to develop new catalyst and cathode in the MFC.

这项研究的目的是调查碱性条件下pH对微生物燃料电池（MFC）阴极生物膜中细菌群落分层的影响。具有空气阴极的单室MFC在0.8、9.5和10.5的pH值下分别使用0.8 g / L麦芽糖糊精和碳酸氢盐缓冲溶液运行。分别通过线性扫描伏安法（LSV），电化学阻抗谱（EIS），共聚焦激光扫描显微镜（CLSM），冷冻切片机和高通量测序对细菌群落进行表征。结果表明，MFC中的最大功率密度随pH值的增加而增加，达到了1221±96 mW / m ^2。在约30天的操作中，pH = 10.5。在不同的pH值下，阴极生物膜的底层（0 – 50μm），中间层（50 – 100μm）和顶层（100 – 150μm）的细菌群落组成和相对丰度显着变化。在pH = 10.5的情况下，好氧细菌分别占顶层，中层和底层细菌群落的12％，13％和34％。顶层和中间层的厌氧细菌数量（分别为细菌群落的52％和50％）高于底层（22％）。好氧和厌氧细菌的分布在各层内显示出“峰谷”结构。高CO ₃ ^2-在高碱性条件下，浓度的增加有助于MFC阳极中的羟基转移和中和。这项研究的结果对于在MFC中开发新的催化剂和阴极应该是有用的。