Promoting direct interspecies electron transfer with activated carbon
Promoting direct interspecies electron transfer with activated carbon
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DOI：
10.1039/c2ee22459c
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发表时间：
2012-10-01
影响因子：
32.5
通讯作者：
Lovley, Derek R.
中科院分区：
文献类型：
--
作者：
Liu, Fanghua;Rotaru, Amelia-Elena;Lovley, Derek R.
将颗粒活性炭 (GAC) 添加到产甲烷消化器中以增强废物向甲烷的转化，但人们对 GAC 刺激作用的机制知之甚少。 GAC 具有高电导率，因此推测 GAC 刺激产甲烷的机制之一可能是促进细菌和产甲烷菌之间的直接种间电子转移 (DIET)。当将 GAC 添加到金属还原地杆菌和硫还原地杆菌的共培养物中时，在先前显示需要饮食的条件下生长，代谢显着加速。细胞附着在 GAC 上，但不会像在细胞之间建立生物电连接时那样聚集。对一系列基因缺失突变体的研究消除了 GAC 通过种间氢或甲酸盐转移促进电子交换的可能性，并证明在 GAC 存在下 DIET 不需要参与生物种间电连接的导电菌毛和相关的 c 型细胞色素。 GAC 还极大地刺激了 G. metallireducens 和 Methanosarcina barkeri 的共培养物中的乙醇代谢和甲烷产生。细胞附着在 GAC 上，但没有紧密聚集，这表明物种之间几乎没有机会进行生物电接触。 GAC 还提高了产甲烷消化池样品中的甲烷产量，其中甲烷菌是主要产甲烷菌。结果表明，GAC 可以促进 DIET，并表明对产甲烷消化器中新陈代谢的刺激至少部分归因于 GAC 的高电导率，提供了比生物锻造更好的种间电连接。
Granular activated carbon (GAC) is added to methanogenic digesters to enhance conversion of wastes to methane, but the mechanism(s) for GAC's stimulatory effect are poorly understood. GAC has high electrical conductivity and thus it was hypothesized that one mechanism for GAC stimulation of methanogenesis might be to facilitate direct interspecies electron transfer (DIET) between bacteria and methanogens. Metabolism was substantially accelerated when GAC was added to co-cultures of Geobacter metallireducens and Geobacter sulfurreducens grown under conditions previously shown to require DIET. Cells were attached to GAC, but did not aggregate as they do when making biological electrical connections between cells. Studies with a series of gene deletion mutants eliminated the possibility that GAC promoted electron exchange via interspecies hydrogen or formate transfer and demonstrated that DIET in the presence of GAC did not require the electrically conductive pili and associated c-type cytochrome involved in biological interspecies electrical connections. GAC also greatly stimulated ethanol metabolism and methane production in co-cultures of G. metallireducens and Methanosarcina barkeri. Cells were attached to GAC, but not closely aggregated, suggesting little opportunity for biological electrical contacts between the species. GAC also enhanced methane production in samples from a methanogenic digester in which Methanosaeta were the predominant methanogens. The results demonstrate that GAC can promote DIET and suggest that stimulation of metabolism in methanogenic digesters can be attributed, at least in part, to the high conductivity of GAC providing better interspecies electrical connections than those that can be forged biologically.