Dynamic responses and adsorption mechanisms of Chlamydomonas reinhardtii extracellular polymeric substances under Cd, Cu, Pb, and Zn exposure

IF 7.6 2区环境科学与生态学 Q1 ENVIRONMENTAL SCIENCES

Environmental Pollution Pub Date : 2025-01-25 DOI:10.1016/j.envpol.2025.125747

Chonghua Li, Peihuan Li, Hongxuan Fu, Zijian She, Chunhua Zhang, Yichun Li, Mu Zhang, Ying Ge

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引用次数: 0

Abstract

Extracellular polymeric substances (EPS) can effectively attenuate heavy metal mobility in aquatic ecosystems and reduce metal toxicity to cells. However, a systematic study of microalgae EPS responses and their adsorption behaviors, characteristics, and mechanisms under different heavy metal exposures has not been performed. In this study, EPS extracted from Chlamydomonas reinhardtii CC-125 was analyzed for compositional changes (monosaccharides and proteins) under Cd, Cu, Pb, and Zn treatments. The EPS adsorption capacities and mechanisms for the four metal ions were also investigated. Cd (10 mg/L), Cu (5 mg/L), and Zn (5 mg/L) exposure induced changes in the microalgal EPS composition and structure, and a protein/polysaccharide ratio of greater than 1 was found. This result indicated the crucial role of proteins in stress resistance. In contrast, Pb stress resulted in an increase of 532.64% and 117.48% in proteins and polysaccharides, respectively, with galactose and glucose playing key roles in this process. A fluorescence analysis revealed that Cd/Pb exposure reduced the tryptophan and tyrosine levels in the EPS, while Cu/Zn only weakened tryptophan. As a biosorbent, the adsorption capacity of the EPS for the four metals followed the order of Pb > Cd > Cu > Zn. The fluorescence quenching titration results revealed that fluorescent compounds in the EPS had the strongest complexation ability with Pb (logK_SV: 8.16 × 10³), followed by Cu (logK_SV: 1.79 × 10³), while their abilities for Cd and Zn were weaker. A spectroscopic analysis indicated that the primary functional groups involved in EPS binding with Pb/Cd and Cd/Zn were protein carboxyl groups (C=O/O-C=O) and glycosidic bonds (C-OH/C-O-C), respectively. This study elucidates the response strategies and adsorption mechanisms of the C. reinhardtii EPS to different metals and provides a basis for environmental heavy metal pollution bioremediation.

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来源期刊

Environmental Pollution 环境科学-环境科学

CiteScore

16.00

自引率

6.70%

发文量

2082

审稿时长

2.9 months

期刊介绍： Environmental Pollution is an international peer-reviewed journal that publishes high-quality research papers and review articles covering all aspects of environmental pollution and its impacts on ecosystems and human health. Subject areas include, but are not limited to: • Sources and occurrences of pollutants that are clearly defined and measured in environmental compartments, food and food-related items, and human bodies; • Interlinks between contaminant exposure and biological, ecological, and human health effects, including those of climate change; • Contaminants of emerging concerns (including but not limited to antibiotic resistant microorganisms or genes, microplastics/nanoplastics, electronic wastes, light, and noise) and/or their biological, ecological, or human health effects; • Laboratory and field studies on the remediation/mitigation of environmental pollution via new techniques and with clear links to biological, ecological, or human health effects; • Modeling of pollution processes, patterns, or trends that is of clear environmental and/or human health interest; • New techniques that measure and examine environmental occurrences, transport, behavior, and effects of pollutants within the environment or the laboratory, provided that they can be clearly used to address problems within regional or global environmental compartments.