Zhu Pingting, Long Guoyu, Ni Jinren, Tong Meiping
School of Environment and Urban Studies, Shenzhen Graduate School of Peking University, Shenzhen 518055, PR China
Environ Sci Technol. 2009 Aug 1;43(15):5699-704. doi: 10.1021/es9003312.
The deposition kinetics of extracellular polymeric substances (EPS) on silica surfaces were examined in both monovalent and divalent solutions under a variety of environmentally relevant ionic strength and pH conditions by employing a quartz crystal microbalance with dissipation (DCM-D). Soluble EPS (SEPS) and bound EPS (BEPS) were extracted from four bacterial strains with different characteristics. Maximum favorable deposition rates (k(fa)) were observed for all EPS at low ionic strengths in both NaCl and CaCl2 solutions. With the increase of ionic strength, k(fa) decreased due to the simultaneous occurrence of EPS aggregation in solutions. Deposition efficiency (alpha; the ratio of deposition rates obtained under unfavorable versus corresponding favorable conditions) for all EPS increased with increasing ionic strength in both NaCl and CaCl2 solutions, which agreed with the trends of zeta potentials and was consistent with the classic Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Comparison of alpha for SEPS and BEPS extracted from the same strain showed that the trends of alpha did not totally agree with trends of zeta potentials, indicating the deposition kinetics of EPS on silica surfaces were not only controlled by DLVO interactions, but also non-DLVO forces. Close comparison of alpha for EPS extracted from different sources showed alpha increased with increasing proteins to polysaccharides ratio. Subsequent experiments for EPS extracted from the same strain but with different proteins to polysaccharides ratios and from activated sludge also showed that alpha were largest for EPS with greatest proteins to polysaccharides ratio. Additional experiments for pure protein and solutions with different pure proteins to pure saccharides ratios further corroborated that larger proteins to polysaccharides ratio resulted in greater EPS deposition.
通过使用带耗散的石英晶体微天平（DCM-D），在各种与环境相关的离子强度和pH条件下，研究了单价和二价溶液中细胞外聚合物（EPS）在二氧化硅表面的沉积动力学。从四种具有不同特性的细菌菌株中提取了可溶性EPS（SEPS）和结合EPS（BEPS）。在NaCl和CaCl2溶液中，所有EPS在低离子强度下均观察到最大有利沉积速率（k(fa)）。随着离子强度的增加，由于溶液中EPS同时发生聚集，k(fa)降低。在NaCl和CaCl2溶液中，所有EPS的沉积效率（α；不利条件下与相应有利条件下获得的沉积速率之比）均随离子强度的增加而增加，这与zeta电位的趋势一致，并且与经典的Derjaguin-Landau-Verwey-Overbeek（DLVO）理论一致。对从同一菌株中提取的SEPS和BEPS的α进行比较表明，α的趋势与zeta电位的趋势并不完全一致，这表明EPS在二氧化硅表面的沉积动力学不仅受DLVO相互作用控制，还受非DLVO力控制。对从不同来源提取的EPS的α进行仔细比较表明，α随蛋白质与多糖比例的增加而增加。随后对从同一菌株中提取但蛋白质与多糖比例不同的EPS以及活性污泥进行的实验也表明，蛋白质与多糖比例最高的EPS的α最大。对纯蛋白质以及不同纯蛋白质与纯糖类比例的溶液进行的额外实验进一步证实，较大的蛋白质与多糖比例会导致更大的EPS沉积。
