Differential ultraviolet-visible absorbance spectra for characterizing metal ions binding onto extracellular polymeric substances in different mixed microbial cultures.
Ultraviolet-visible (UV-vis) absorbance spectra was adopted to quantify the binding of major metal ions (e.g., Na(I), Ca((II)), Fe(III), Cu(II), and Pb(II)) on extracellular polymeric substances (EPSs) extracted from different mixed cultures. The results showed that the differential absorbance spectra (DAS) provided discernible features for revealing the changes in optical properties of EPSs induced by metals, i.e., the intensity of DAS increased largely with incrementally increased metal concentrations (Fe(III), Cu(II), and Pb(II)). It can be assumed attributable to the changes in the conformations and inter-chromophores of the EPS biomolecules. In addition, the changes in spectral parameters of DSlope325-375 (spectral slope in the range of wavelengths 325-375 nm) and DA300 (differential absorbance at 300 nm) were found to be closely related to the amounts of metals bound onto all extracted EPSs, particularly for Fe(III) and Cu(II). The decreased SR (the ratio of slope275-295 to slope350-400) of the EPS solutions after dosage of metals suggested increased molecular weight or size of the EPS biomolecules. Deconvolution of the DAS yielded six Gaussian bands, which were present in all of the EPS samples with various metals. Moreover, the relative contributions of different Gaussian bands in the DAS were determined by the nature of EPS-metal ions interactions good correlated with the covalent-bonding index. This study concluded that DAS and selected spectral parameters (DA300, DSlope325-375 and SR) can be used to successfully characterize the binding of metals onto EPS at environmentally relevant concentrations.
School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, PR China.
Cuiqin
C
Yin
School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, PR China. Electronic address: mengfg@mail.sysu.edu.cn.
Fangang
F
Meng
School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, PR China; Guangdong Provincial Key Laboratory of Environmental Pollution Control and Remediation Technology, Sun Yat-sen University, Guangzhou 510275, PR China.
Yabing
Y
Meng
School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou 510275, PR China; Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, PR China. Electronic address: ceghchen@ust.hk.
Guang-Hao
GH
Chen
D001419:Bacteria / Q000378:metabolism*; D005290:Ferric Compounds / Q000737:chemistry; D007477:Ions; D008670:Metals / Q000737:chemistry*; D011108:Polymers / Q000378:metabolism*; D013057:Spectrum Analysis; D014466:Ultraviolet Rays
D005290:Ferric Compounds; D007477:Ions; D008670:Metals; D011108:Polymers
Extracellular polymeric substances; Gaussian bands; Metal ions; Ultraviolet–visible absorbance spectra