Spectroscopic fingerprints profiling the polysaccharide/protein/humic architecture of stratified extracellular polymeric substances (EPS) in activated sludge

Jinlan Yu; Kang Xiao; Hao Xu; Yitong Li; Qiao Xue; Wenchao Xue; Aiqian Zhang; Xianghua Wen; Guoren Xu; Xia Huang

doi:10.1016/j.watres.2023.119866

Spectroscopic fingerprints profiling the polysaccharide/protein/humic architecture of stratified extracellular polymeric substances (EPS) in activated sludge

Water Res. 2023 May 15:235:119866. doi: 10.1016/j.watres.2023.119866. Epub 2023 Mar 12.

Authors

Jinlan Yu¹, Kang Xiao², Hao Xu³, Yitong Li⁴, Qiao Xue⁵, Wenchao Xue⁶, Aiqian Zhang⁵, Xianghua Wen⁷, Guoren Xu³, Xia Huang⁸

Affiliations

¹ Beijing Yanshan Earth Critical Zone National Research Station, University of Chinese Academy of Sciences, Beijing 101408, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 101408, China; State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China.
² Beijing Yanshan Earth Critical Zone National Research Station, University of Chinese Academy of Sciences, Beijing 101408, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 101408, China. Electronic address: kxiao@ucas.ac.cn.
³ College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 101408, China.
⁴ Beijing Yanshan Earth Critical Zone National Research Station, University of Chinese Academy of Sciences, Beijing 101408, China.
⁵ State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
⁶ Department of Energy, Environment, and Climate Change, School of Environment, Resources, and Development, Asian Institute of Technology, P.O. Box 4, Klong Luang, Pathumthani 12120, Thailand.
⁷ State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China. Electronic address: xhwen@tsinghua.edu.cn.
⁸ State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China.

PMID: 36934542
DOI: 10.1016/j.watres.2023.119866

Abstract

Extracellular polymeric substances (EPS), with a stratified structure including tightly-bound EPS (TB-EPS), loosely-bound EPS (LB-EPS), and soluble EPS (S-EPS) surrounding the microbial cells, are known to vitally affect the physicochemical and biological functions of activated sludge in wastewater treatment. Polysaccharides (PS), proteins (PN), and humic acids (HA) are key components of EPS but their roles in constructing the multi-layer architecture are still unclear. This study explored the EPS characteristics in relation to the components using spectroscopic fingerprinting techniques. Ultraviolet-visible (UV-vis) spectra demonstrated stark difference between TB-EPS and other EPS. Fluorescence excitation-emission matrix (FEEM) and apparent quantum yield revealed further detailed differences. Fluorescence quotient analysis highlighted the dominance of TB-EPS, LB-EPS, and S-EPS in the excitation/emission wavelength (Ex/Em) region of Em = 350-400 nm, Em > 400 nm, and low-Stokes shift band (Em - Ex < 25 nm), respectively. Wavelength-wise prediction of the FEEM intensity was achieved through multiple linear regression against the chemical composition and variance partitioning analysis witnessed binary interactions of PS×HA and PS×PN in S-EPS, PN×HA and PS×PN in LB-EPS, and ternary interaction of PS×PN×HA in TB-EPS as well as the wavelength-specific fluorescence responses of these interactions. Further, X-ray photoelectron spectroscopy, infrared spectra, and circular dichroism spectra corroborated the differences in primary, secondary, and tertiary structures across the EPS layers. Ultrahigh-performance liquid chromatography-mass spectrometry detected molecular fragments confirming the multi-component hybridization among PS, PN, and HA. This study demonstrates a spectroscopic approach to sensitively fingerprint the fine structure of EPS, which has the potential for rapid monitoring of EPS and related sludge properties in wastewater treatment systems.

Keywords: Activated sludge; Extracellular polymeric substances; Fluorescence excitation-emission matrix; Organic component characteristics; Statistical analysis; Ultraviolet-visible spectra.

MeSH terms

Extracellular Polymeric Substance Matrix* / chemistry
Polysaccharides / analysis
Proteins / analysis
Sewage* / chemistry
Spectrum Analysis

Substances

Sewage
Polysaccharides
Proteins