Klebisella还原合成纳米钯的电子传递途径解析

The electron transfer research of biogenic nano-palladium by Klebsiella strain

以甲酸钠为电子供体,利用化学法和生物法制备了2种纳米钯颗粒,分别为化学合成钯(Chem-Pd)和生物合成钯(Bio-Pd).对两种钯颗粒进行表征,透射电子显微镜(TEM)和X射线衍射(XRD)结果表明Chem-Pd颗粒为团聚态,平均粒径为12nm,而Bio-Pd均匀地分布在细胞内部和胞外聚和物(EPS)上,平均尺寸为5nm.二价钯还原曲线表明相比于化学法,利用生物法还原二价钯的速率提高了70%,说明微生物的介入可有效促进纳米钯的生成.通过探究胞内电子传递和胞外聚合物对合成Bio-Pd的作用,阐明了Bio-Pd合成机理为Klebisella oxytoca通过自身呼吸链传递将电子传递给胞外的二价钯,同时细菌分泌的EPS中存在氧化还原活性基团在胞外促进合成纳米钯.活死菌染色实验表明Bio-Pd对微生物仍具有一定的毒害作用.

Chem-Pd(chemically synthesized palladium nanoparticle)and Bio-Pd(biosynthetic palladium nanoparticle)were prepared using chemical and biological methods,respectively,with sodium formate serving as the electron donor.The TEM and XRD results revealed that the Chem-Pd was agglomerated with an average particle size of 12nm,while Bio-Pd was evenly distributed inside the cell and in the extracellular polymeric substance(EPS),with an average size of 5nm.The reduction curve of bivalent palladium showed that the rate of bivalent palladium reduction by the biological method was 70%higher than that by the chemical method,indicating that the intervention of microorganisms can effectively promote the formation of nano palladium.By exploring the effect of intracellular electron transfer and extracellular polymer on the synthesis of Bio-Pd,the synthesis mechanism of Bio-Pd was clarified:the Klebsiella oxytoca strain transferred electrons to extracellular palladium divalent via its respiratory chain.Meanwhile,the presence of redox active groups in EPS may enhance Bio-Pd production outside the cell.Additionally,the test of live/dead bacteria showed that Bio-Pd remained harmful to cells.