De Windt Wim, Boon Nico, Van den Bulcke Jan, Rubberecht Leen, Prata Filipa, Mast Jan, Hennebel Tom, Verstraete Willy
Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Coupure Links 653, B-9000, Gent, Belgium.
Antonie Van Leeuwenhoek. 2006 Nov;90(4):377-89. doi: 10.1007/s10482-006-9088-4. Epub 2006 Oct 11.
The interaction between Shewanella oneidensis MR-1 and the soluble metal Pd(II) during the reductive precipitation of Pd(0) determined the size and properties of the precipitated Pd(0) nanoparticles. Assessment of cell viability indicated that the bioreduction of Pd(II) was a detoxification mechanism depending on the Pd(II) concentration and on the presence and properties of the electron donor. The addition of H(2) in the headspace allowed S. oneidensis to resist the toxic effects of Pd(II). Interestingly, 25 mM formate was a less effective electron donor for bioreductive detoxification of Pd(II), since there was a 2 log reduction of culturable cells and a 20% decrease of viable cells within 60 min, followed by a slow recovery. When the ratio of Pd:cell dry weight (CDW) was below 5:2 at a concentration of 50 mg l(-1) Pd(II), most of the cells remained viable. These viable cells precipitated Pd(0) crystals over a relatively larger bacterial surface area and had a particle area that was up to 100 times smaller when compared to Pd(0) crystals formed on non-viable biomass (Pd:CDW ratio of 5:2). The relatively large and densely covering Pd(0) crystals on non-viable biomass exhibited high catalytic reactivity towards hydrophobic molecules such as polychlorinated biphenyls, while the smaller and more dispersed nanocrystals on a viable bacterial carrier exhibited high catalytic reactivity towards the reductive degradation of the anionic pollutant perchlorate.
在零价钯（Pd(0)）的还原沉淀过程中，希瓦氏菌MR-1（Shewanella oneidensis MR-1）与可溶性金属钯（II）（Pd(II)）之间的相互作用决定了沉淀出的零价钯纳米颗粒的尺寸和性质。细胞活力评估表明，Pd(II)的生物还原是一种解毒机制，这取决于Pd(II)的浓度以及电子供体的存在和性质。在顶空中添加氢气（H₂）可使希瓦氏菌抵抗Pd(II)的毒性作用。有趣的是，25 mM的甲酸盐作为电子供体对Pd(II)进行生物还原解毒的效果较差，因为在60分钟内可培养细胞数量减少了2个对数级，活细胞数量减少了20%，随后是缓慢恢复。当Pd(II)浓度为50 mg l⁻¹时，若Pd与细胞干重（CDW）的比例低于5:2，则大多数细胞仍保持活力。这些活细胞在相对较大的细菌表面积上沉淀出Pd(0)晶体，与在无活力生物质上形成的Pd(0)晶体（Pd:CDW比例为5:2）相比，其颗粒面积小至100倍。无活力生物质上相对较大且密集覆盖的Pd(0)晶体对多氯联苯等疏水性分子表现出高催化活性，而活细菌载体上较小且更分散的纳米晶体对阴离子污染物高氯酸盐的还原降解表现出高催化活性。
