Rehman Zahid Ur, Vrouwenvelder Johannes S, Saikaly Pascal E
Water Desalination and Reuse Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.
Front Microbiol. 2021 Jul 13;12:668761. doi: 10.3389/fmicb.2021.668761. eCollection 2021.
This work describes the chemical composition of extracellular polymeric substances (EPS) produced by three bacteria (RO1, RO2, and RO3) isolated from a biofouled reverse osmosis (RO) membrane. We isolated pure cultures of three bacterial strains from a 7-year-old biofouled RO module that was used in a full-scale seawater treatment plant. All the bacterial strains showed similar growth rates, biofilm formation, and produced similar quantities of proteins and polysaccharides. The gel permeation chromatography showed that the EPS produced by all the strains has a high molecular weight; however, the EPS produced by strains RO1 and RO3 showed the highest molecular weight. Fourier Transform Infrared Spectroscopy (FTIR), Proton Nuclear Magnetic Resonance (H NMR), and Carbon NMR (C NMR) were used for a detailed characterization of the EPS. These physicochemical analyses allowed us to identify features of EPS that are important for biofilm formation. FTIR analysis indicated the presence of α-1,4 glycosidic linkages (920 cm) and amide II (1,550 cm) in the EPS, the presence of which has been correlated with the fouling potential of bacteria. The presence of α-glycoside linkages was further confirmed by C NMR analysis. The C NMR analysis also showed that the EPS produced by these bacteria is chemically similar to foulants obtained from biofouled RO membranes in previous studies. Therefore, our results support the hypothesis that the majority of substances that cause fouling on RO membranes originate from bacteria. Investigation using H NMR showed that the EPS contained a high abundance of hydrophobic compounds, and these compounds can lead to flux decline in the membrane processes. Genome sequencing of the isolates showed that they represent novel species of bacteria belonging to the genus . Examination of genomes showed that these bacteria carry carbohydrates-active enzymes that play a role in the production of polysaccharides. Further genomic studies allowed us to identify proteins involved in the biosynthesis of EPS and flagella involved in biofilm formation. These analyses provide a glimpse into the physicochemical properties of EPS found on the RO membrane. This knowledge can be useful in the rational design of biofilm control treatments for the RO membrane.
本研究描述了从生物污染的反渗透（RO）膜中分离出的三种细菌（RO1、RO2和RO3）产生的细胞外聚合物（EPS）的化学成分。我们从一个在大型海水处理厂中使用了7年的生物污染RO组件中分离出了三种细菌菌株的纯培养物。所有细菌菌株的生长速率、生物膜形成情况相似，且产生的蛋白质和多糖数量相近。凝胶渗透色谱分析表明，所有菌株产生的EPS具有高分子量；然而，RO1和RO3菌株产生的EPS分子量最高。采用傅里叶变换红外光谱（FTIR）、质子核磁共振（H NMR）和碳核磁共振（C NMR）对EPS进行了详细表征。这些物理化学分析使我们能够确定对生物膜形成重要的EPS特征。FTIR分析表明EPS中存在α-1,4糖苷键（920 cm）和酰胺II（1,550 cm），其存在与细菌的污染潜力相关。C NMR分析进一步证实了α-糖苷键的存在。C NMR分析还表明，这些细菌产生的EPS在化学上与先前研究中从生物污染RO膜中获得的污垢物质相似。因此，我们的结果支持了这样一种假设，即导致RO膜污染的大多数物质源自细菌。利用H NMR进行的研究表明，EPS含有大量疏水性化合物，这些化合物会导致膜过程中的通量下降。分离菌株的基因组测序表明，它们代表了属于该属的新型细菌物种。对基因组的检查表明，这些细菌携带参与多糖生产的碳水化合物活性酶。进一步的基因组研究使我们能够鉴定参与EPS生物合成的蛋白质以及参与生物膜形成的鞭毛。这些分析让我们得以一窥RO膜上EPS的物理化学性质。这些知识对于合理设计RO膜生物膜控制处理方法可能会有所帮助。
