Variation in Extracellular Polymeric Substances from Enterobacter sp. and Their Pb²⁺ Adsorption Behaviors

Abstract

The objective of this study was to investigate the effects of the cultivation time, temperature, and pH value on the yield and composition of extracellular polymeric substances (EPS) from Enterobacter sp. FM-1 (FM-1) and to analyze the Pb 2+ adsorption behavior of soluble EPS (S-EPS), loosely bound EPS (LB-EPS), and tightly bound EPS (TB-EPS). Maximum EPS production was obtained when the cultivation time, temperature, and pH value were 24 h, 30 °C, and 8.0, respectively. The main components of EPS were proteins, polysaccharides, and nucleic acids, but the different EPS types contained different proportions and specific components. The Pb 2+ adsorption capacity of LB-EPS was 2.23 and 1.50 times higher than that of S-EPS and TB-EPS, respectively. After Pb 2+ adsorption by LB-EPS, the pH value of the reaction system decreased to the lowest of 5.23, which indicated that LB-EPS contained more functional groups that could release H + , which will help to better adsorb Pb 2+ through ion exchange. The three-dimensional excitation–emission matrix fluorescence spectroscopy (3D-EEM) analysis showed that the fluorescence intensity of tryptophan-containing substances decreased by 85.5% after Pb 2+ adsorption by LB-EPS, which indicated the complexation of tryptophan-containing substances with Pb 2+ . Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) O spectra indicated that the C=O peak from protein amide I of tryptophan-containing substances in LB-EPS was mainly responsible for the complexation of Pb 2+ . After the adsorption of Pb 2+ , the proportion of the C=O peak in LB-EPS increased by 33.89%, indicating that the complexation of LB-EPS with Pb 2+ was mainly attributed to the O atom in the C=O terminus of protein amide I.

Extracellular Polymeric Substances (EPS) as Microalgal Bioproducts: A Review of Factors Affecting EPS Synthesis and Application in Flocculation Processes

“…LB-EPS and TB-EPS show a different composition and functionalities. As reported by Li et al (2020), LB-EPS show the highest Pb(II) adsorption abilities in comparison to TB-EPS and SB-EPS (soluble EPS) [9]. The role of LB-EPS seems to be more important in response to adverse environmental changes than the role of other EPS fractions; hence, they serve a protection function in algal metabolism [10].…”

Effects of desloratadine on activated sludge: Behaviour of EPS and sludge properties

“…Several studies have demonstrated that changes in the operational parameters (pH, temperature, toxic compounds, etc.) might affect the yield and composition of different fractions of EPS produced by microorganisms [45,46]. In our research, LB-and TB-EPS contained a large portion of proteins (PN/PS ratio = 1.0 -2.5, and 1.6 -3.6, respectively).…”

Simultaneous nitrogen and phosphorus removal from domestic wastewater in an aerobic granulation system operated at different anaerobic–aerobic durations

“…There have also been diverse opinions and results among researchers on the role of different EPS compositions, particularly PN and PS of EPS, in aerobic granulation. 50,51 According to Rusanowska et al (2019) and Oliveira et al (2020), the PN in EPS serves the function of enhancing microbial aggregation, maintaining the structural stability and protecting the biomass against environmental stress and dehydration. 46,52 Extracellular PS is vital in maintaining the strength and cell-tocell interaction of aerobic granules.…”