School of Metallurgy and Environment, Central South University, Changsha 410083, China; Department of Science and Environmental Studies, The Education University of Hong Kong, Hong Kong 999077, China.
School of Metallurgy and Environment, Central South University, Changsha 410083, China.
J Environ Sci (China). 2023 Aug;130:187-196. doi: 10.1016/j.jes.2022.10.004. Epub 2022 Oct 17.
Extracellular polymeric substances (EPS) are an important medium for communication and material exchange between iron-oxidizing bacteria and the external environment and could induce the iron (oxyhydr) oxides production which reduced arsenic (As) availability. The main component of EPS secreted by iron-oxidizing bacteria (Ochrobactrum EEELCW01) was composed of polysaccharides (150.76-165.33 mg/g DW) followed by considerably smaller amounts of proteins (12.98-16.12 mg/g DW). Low concentrations of As (100 or 500 µmol/L) promoted the amount of EPS secretion. FTIR results showed that EPS was composed of polysaccharides, proteins, and a miniscule amount of nucleic acids. The functional groups including -COOH, -OH, -NH, -C=O, and -C-O played an important role in the adsorption of As. XPS results showed that As was bound to EPS in the form of As. With increasing As concentration, the proportion of As adsorbed on EPS increased. Ferrihydrite with a weak crystalline state was only produced in the system at 6 hr during the mineralization process of Ochrobactrum sp. At day 8, the minerals were composed of goethite, galena, and siderite. With the increasing mineralization time, the main mineral phases were transformed from weakly crystalline hydrous iron ore into higher crystallinity siderite (FeCO) or goethite (α-FeOOH), and the specific surface area and active sites of minerals were reduced. It can be seen from the distribution of As elements that As is preferentially adsorbed on the edges of iron minerals. This study is potential to understand the biomineralization mechanism of iron-oxidizing bacteria and As remediation in the environment.
胞外聚合物（EPS）是铁氧化菌与外界环境进行物质交换和信息传递的重要介质，可诱导铁（氧）氢氧化物的生成，从而降低砷的有效性。铁氧化菌（Ochrobactrum EEELCW01）分泌的 EPS 的主要成分是多糖（150.76-165.33mg/gDW），其次是相对较小量的蛋白质（12.98-16.12mg/gDW）。低浓度的砷（100 或 500μmol/L）会促进 EPS 的分泌。FTIR 结果表明，EPS 由多糖、蛋白质和少量核酸组成。-COOH、-OH、-NH、-C=O 和 -C-O 等功能基团在砷的吸附过程中发挥了重要作用。XPS 结果表明，砷以 As 的形式结合到 EPS 上。随着砷浓度的增加，吸附在 EPS 上的砷比例增加。在 Ochrobactrum 属的矿化过程中，只有在 6 小时的系统中才会生成弱结晶状态的水铁矿。在第 8 天，矿物由黄铁矿、方铅矿和菱铁矿组成。随着矿化时间的增加，主要矿物相从弱结晶水铁矿转变为更高结晶度的菱铁矿（FeCO）或针铁矿（α-FeOOH），并且矿物的比表面积和活性位点减少。从砷元素的分布可以看出，砷优先吸附在铁矿物的边缘。这项研究有助于理解铁氧化菌的生物矿化机制和环境中砷的修复。
