Involvement of hydrogenases in the formation of highly catalytic Pd(0) nanoparticles by bioreduction of Pd(II) using Escherichia coli mutant strains
Involvement of hydrogenases in the formation of highly catalytic Pd(0) nanoparticles by bioreduction of Pd(II) using Escherichia coli mutant strains
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DOI：
10.1099/mic.0.036681-0
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发表时间：
2010-09-01
期刊：
影响因子：
2.8
通讯作者：
Macaskie, Lynne E.
中科院分区：
文献类型：
--
作者：
Deplanche, Kevin;Caldelari, Isabelle;Macaskie, Lynne E.
大肠杆菌至少产生三种[nife]氢酶(hyd-1、hyd-2和hyd-3)。HYD-1和HYD-2是膜结合的呼吸同工酶，其催化亚基暴露在膜的周质侧。HYD-3是细胞质导向的甲酸氢解酶复合体的一部分。在这项工作中，研究了这些氢酶在酸性(pH 2.4)条件下Pd(II)还原中的作用。虽然这三种氢酶都可以促进Pd(II)的还原，但需要存在周质氢酶(HYD-1或HYD-2)才能观察到与亲本菌株相当的Pd(II)还原速率。一株在遗传上丧失了所有氢酶活性的大肠杆菌突变株对Pd(II)的减少可以忽略不计。电子显微镜显示，由此产生的Pd(0)沉积的位置与预期的一样，是因为参与还原过程的特定氢酶的亚细胞定位。膜分离实验证明，Pd(II)还原酶的活性是膜结合的，需要氢酶来启动Pd(II)的还原。所得到的Pd(0)纳米粒子在将铬(VI)还原为铬(III)方面的催化活性因用于Pd(II)初始生物还原的大肠杆菌突变株而异。从含有活性HYD-1的菌株制备生物Pd(0)催化剂颗粒时，观察到了与商业Pd催化剂相当的最佳Cr(VI)还原。在经济生产新型纳米金属催化剂的背景下对结果进行了讨论。
Escherichia coli produces at least three [NiFe] hydrogenases (Hyd-1, Hyd-2 and Hyd-3). Hyd-1 and Hyd-2 are membrane-bound respiratory isoenzymes with their catalytic subunits exposed to the periplasmic side of the membrane. Hyd-3 is part of the cytoplasmically oriented formate hydrogenlyase complex. In this work the involvement of each of these hydrogenases in Pd(II) reduction under acidic (pH 2.4) conditions was studied. While all three hydrogenases could contribute to Pd(II) reduction, the presence of either periplasmic hydrogenase (Hyd-1 or Hyd-2) was required to observe Pd(II) reduction rates comparable to the parent strain. An E. coli mutant strain genetically deprived of all hydrogenase activity showed negligible Pd(II) reduction. Electron microscopy suggested that the location of the resulting Pd(0) deposits was as expected from the subcellular localization of the particular hydrogenase involved in the reduction process. Membrane separation experiments established that Pd(II) reductase activity is membrane-bound and that hydrogenases are required to initiate Pd(II) reduction. The catalytic activity of the resulting Pd(0) nanoparticles in the reduction of Cr(VI) to Cr(III) varied according to the E. coli mutant strain used for the initial bioreduction of Pd(II). Optimum Cr(VI) reduction, comparable to that observed with a commercial Pd catalyst, was observed when the bio-Pd(0) catalytic particles were prepared from a strain containing an active Hyd-1. The results are discussed in the context of economic production of novel nanometallic catalysts.