State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, China.
State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, China; University of Chinese Academy of Sciences, Beijing, China.
Sci Total Environ. 2020 May 1;715:136959. doi: 10.1016/j.scitotenv.2020.136959. Epub 2020 Jan 27.
Cyanobacterial extracellular polymeric substances (EPSs) in aquatic environments are easily adsorbed onto colloidal particles, whereas the adsorption behavior as affected by molecular weight (MW) properties remained unknown till now. Herein, the bulk cyanobacterial EPS matrix (<0.45 μm) was fractionated into high MW (HMW-, 1 kDa~0.45 μm) and low MW (LMW-, <1 kDa) fractions, with MW-dependent adsorption heterogeneities onto TiO colloids exploring through batch experiment, UV-Vis and fluorescence spectroscopy, and two dimensional Fourier transform infrared correlation spectroscopy (2D-FTIR-COS). About two-thirds of total organic matters within bulk EPS matrix were distributed in the HMW fraction, leaving one-third in the LMW fraction. Compared to LMW-EPS, the HMW counterpart exhibited higher aromaticity and richness of autochthonous protein-like substances, showing evident MW-dependent differences in abundance and composition. The adsorption capacity based on the measurement of total abundance, UV-Vis and fluorescent spectra all decreased in sequence of HMW- > Bulk > LMW-EPS, demonstrating obvious MW-dependent adsorption heterogeneities. During adsorption, the values of SUVA in residual supernatants exhibited an initial decrease followed by gradual increase for all samples, suggesting that the preferentially adsorbed aromatic substances can be subsequently replaced by the non-aromatic moieties. 2D-FTIR-COS further revealed that the carboxylic groups of proteins were preferentially adsorbed onto colloidal surface, followed by the CC functional groups and then the CH groups of polysaccharides, which accounted for the variations of SUVA values in the supernatants. This study demonstrated that the adsorption behavior of EPS matrix was highly MW-dependent, and detailed characterization on size fractionation is thus needed in future studies.
水生态环境中的蓝藻细胞外聚合物（EPS）易被胶体颗粒吸附，然而，其分子量（MW）特性对吸附行为的影响目前仍不清楚。在此，我们将大分子量（HMW-，1 kDa~0.45 μm）和低分子量（LMW-，<1 kDa）的蓝藻 EPS 基质（<0.45 μm）进行分级，通过批实验、紫外可见光谱和荧光光谱以及二维傅里叶变换相关光谱（2D-FTIR-COS）探索 MW 对 TiO2 胶体吸附的影响。约 2/3 的 EPS 基质中的总有机物分布在 HMW 级分中，剩余的 1/3 分布在 LMW 级分中。与 LMW-EPS 相比，HMW-EPS 具有更高的芳香性和丰富的内源性蛋白样物质，在丰度和组成上表现出明显的 MW 依赖性差异。基于总丰度、紫外可见光谱和荧光光谱测量的吸附容量依次降低为 HMW- > 基质 > LMW-EPS，表明存在明显的 MW 依赖性吸附异质性。在吸附过程中，所有样品的剩余上清液中 SUVA 值最初降低，随后逐渐增加，表明优先吸附的芳香族物质随后可被非芳香族取代。2D-FTIR-COS 进一步表明，蛋白质的羧基基团优先被吸附到胶体表面，然后是 CC 官能团，最后是多糖的 CH 基团，这解释了上清液中 SUVA 值的变化。本研究表明 EPS 基质的吸附行为高度依赖于 MW，因此在未来的研究中需要对分级进行详细的特征描述。
