Adsorption of Extracellular Polymeric Substances Derived from S. cerevisiae to Ceria Nanoparticles and the Effects on Their Colloidal Stability
Adsorption of Extracellular Polymeric Substances Derived from S. cerevisiae to Ceria Nanoparticles and the Effects on Their Colloidal Stability
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DOI：
10.3390/environments4030048
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发表时间：
2017-07
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通讯作者：
Shota Masaki;Yuriko Nakano;Kenta Ichiyoshi;Keisuke Kawamoto;Ayaka Takeda;T. Ohnuki;M. Hochella;S. Utsunomiya
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作者：
Shota Masaki;Yuriko Nakano;Kenta Ichiyoshi;Keisuke Kawamoto;Ayaka Takeda;T. Ohnuki;M. Hochella;S. Utsunomiya
为了了解微溶CeO 2纳米颗粒（CeNPs）对酵母菌胞外聚合物（EPS）组分的吸附偏好，在室温（25 ± 1 °C）、pH 6.0条件下，对含有低分子量有机物的EPS进行了吸附实验。涂层对CeNPs结晶的后续影响作为时间和1至1000 mmol L-1范围内的离子强度的函数进行系统测量。在EPS和其他组分中，正磷酸盐和正磷酸盐优先吸附到CeNP上，并且蛋白质是唯一吸附到CeNP表面上的主要N-化合物。正磷酸盐的吸附导致pH > 5时的电位急剧下降至−40 mV，而EPS的吸附在pH 3至11范围内将电位偏差抑制在一个很窄的范围内（−20-+20 mV）。电解质（NaCl）、无机正磷酸盐和EPS溶液的临界聚集浓度（CAC）分别为0.01、0.14和0.25 mol L-1，表明EPS吸附通过源自吸附的正磷酸盐的静电排斥力和由纳米颗粒表面上的有机物质形成的空间位阻来抑制CeNPs的聚集。因此，S. cerevisiae可以潜在地增强CeNPs在中性附近pH下的胶体吸附。
In order to understand the adsorption preferences of extracellular polymeric substances (EPS) components derived from fungus Saccharomyces cerevisiae on sparingly soluble CeO2 nanoparticles (CeNPs), the adsorption experiments of the EPS including organic matter with low molecular weight have been performed at pH 6.0 at room temperature (25 ± 1 °C). The subsequent effects of the coating on the dispersibility of CeNPs was systematically measured as a function of time and ionic strength ranging from 1 to 1000 mmol L−1. Among the EPS and other components, orthophosphate and saccharides preferentially adsorb onto CeNPs, and proteins are the only major N-compounds adsorbing onto the CeNP surfaces. Adsorption of orthophosphate resulted in a dramatic decrease in ζ potential to −40 mV at pH > 5, whereas the EPS adsorption suppressed the deviation of ζ potential within a narrow range (−20–+20 mV) at pHs ranging from 3 to 11. Critical aggregation concentrations (CAC) of an electrolyte (NaCl), inorganic orthophosphate, and EPS solutions are 0.01, 0.14, and 0.25 mol L−1, respectively, indicating that the EPS adsorption suppresses aggregation of CeNPs by the electrostatic repulsive forces derived from the adsorbed orthophosphate and the steric barrier formed by organic matter on the nanoparticle surfaces. Therefore, the EPS derived from fungus S. cerevisiae can potentially enhance colloidal dispersibility of CeNPs at circumneutral pH.