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Phytochelatins of Cladophora rupestris in Pb2+ absorption and its detoxification

Zhang Lu-Sheng, Yang Liu, Li Lingsheng, Feng Xiaoyu, Cao De-Ju, Liu Zhao-Wen

Environment Protection Engineering

2023

Vol. 49, nr 3

31--42

Phytochelatins (PCs) exist widely in plants and are closely related to plant resistance to heavy metals (HMs). Glutathione (GSH) and nonprotein thiols (NPTs) are the major components of PCs. This study investigates the role of the PCs of Cladophora rupestris in Pb2+ accumulation and detoxification. The distribution of Pb2+ in the PCs of C. rupestris was studied. FTIR and XPS are used to characterize the chelating power of Pb2+ with PCs in C.rupestris. The curve fitting of the secondary protein structure is used to identify the functional groups with Pb2+. Results showed that the content of Pb2+ in the PCs of C. rupestris increased with an increase in Pb2+ stress. Pb content increased to 352 and 314 mg/kg in NPTs and GSH, respectively, when Pb stress concentration reached 7.5 mg/dm3 . The Pb2+ fraction of C. rupestris PCs reached a maximum of 10.8 and 9.3% in NPTs and GSH, respectively. The Pb2+ uptake by GSH and NPTs was 40–48% and 52–60%, respectively. Pb2+ bound with the PCs of C. rupestris, forming complexes that contained Pb–OOC, Pb–C=O, CO–Pb, –N=Pb, Pb–NH2, Pb–O, Pb–N–, Pb–C–, Pb–S, and Pb2+ with multiple groups of PCs as bridging ligand atoms.

Comparison of packing media on stratified EPS and their role in the biofilm of trickling biofilter

Dong Bei, Zheng Jie, Wen Yi-Zheng, Lei Xian-Yan, Zhang Qian, Cao De-Ju

Environment Protection Engineering

2021

Vol. 47, nr 3

25--36

The research focused on such packing media as ceramsite, polypropylene balls, and elastic fillers, and analyzed the main characteristics of extracellular polymeric substances (EPS) in their filter biofilms. The EPS were categorized as soluble EPS (S-EPS) and bound EPS (B-EPS). The component characteristics of stratified EPS were investigated via UV-Vis spectroscopy and a three-dimensional excitation-emission matrix (3D-EEM). The results showed that the EPS content of ceramsite biofilm was 245.2 mg/g VSS, which was higher than those of elastic filler material and polypropylene ball by 1.26 and 1.51 times, respectively. The protein (PN) and polysaccharide (PS) ratio of EPS in the ceramsite filter material was highest in S-EPS and B-EPS, indicating that the EPS have a stable structure. More than 67.58% of EPS formed by ceramsite was tightly bound EPS (TB-EPS), which was beneficial to maintaining the stability of biofilms. The levels of proteins (PN) and humic substances formed by ceramsite contained in the TB-EPS were higher than those of elastic filter material and polypropylene balls. 3D-EEM fluorescence spectra revealed that TB-EPS formed by a ceramsite contained high concentrations of tryptophan, tyrosine, and humic substances. The dehydrogenase activity of biofilm formed by ceramsite filler was higher than that formed by elastic fillers and polypropylene balls.