Preliminary characterization of bound extracellular polymeric substances（bEPS） of cyanobacteria is crucial to obtain a better understanding of the formation mechanism of cyanobacterial bloom. However,the characteriz...Preliminary characterization of bound extracellular polymeric substances（bEPS） of cyanobacteria is crucial to obtain a better understanding of the formation mechanism of cyanobacterial bloom. However,the characterization of bEPS can be affected by extraction methods. Five sets（including the control） of bEPS from Microcystis extracted by different methods were characterized using three-dimensional excitation and emission matrix（3DEEM） fluorescence spectroscopy combined chemical spectrophotometry; and the characterization results of bEPS samples were further compared. The agents used for extraction were NaOH,pure water and phosphate buffered saline（PBS） containing cationic exchange resins,and hot water. Extraction methods affected the fluorescence signals and intensities in the bEPS. Five fluorescence peaks were observed in the excitation and emission matrix fluorescence spectra of bEPS samples. Two peaks（peaks T1 and T2） present in all extractions were identified as protein-like fluorophores,two（peaks A and C） as humic-like fluorophores,and one（peak E） as a fulvic-like substance.Among these substances,the humic-like and fulvic-like fluorescences were only seen in the bEPS extracted with hot water. Also,NaOH solution extraction could result in strong fluorescence intensities compared to the other extraction methods. It was suggested that NaOH at pH 10.0 was the most appropriate method to extract bEPS from Microcystis. In addition,dialysis could affect the yields and characteristics of extracted bEPS during the determination process. These results will help us to explore the issues of cyanobacterial blooms.展开更多
Bound extracellular polymeric substances(bEPS)play an important role in the proliferation of Microcystis.However,the understanding of bEPS characterization remains limited.In this study,threedimensional fluorescence e...Bound extracellular polymeric substances(bEPS)play an important role in the proliferation of Microcystis.However,the understanding of bEPS characterization remains limited.In this study,threedimensional fluorescence excitation-emission matrix(3D-EEM)spectroscopy and zeta potentiometer were used to characterize the loosely bound EPS(LB-EP S)and tightly bound EPS(TB-EPS)from two dominant Microcystis morphospecies from Taihu Lake(China)at different light intensities.Physiochemical analysis showed that the growth and TB-EPS or bEPS contents in Microcystis aeruginosa were higher than those in Microcystisfl os-aquae at each light intensity.The 3D-EEM contour demonstrated that the intensities of peak B(tryptophan-like substances)in the TB-EPS from M.aeruginosa were stronger than those from M.flosaquae when the light intensity was higher than 10μE/(m^(2)·s).Zeta potential analysis showed that the absolute values of the zeta potential of TB-EPS in the two species both increased with rising light intensity,except those of TB-EPS in M.aeruginosa at 105μE/(m^(2)·s).Moreover,the absolute values of the zeta potential of M.aeruginosa were higher than tho se of M.flos-aquae at each light intensity.All these re sults indicated that M.aeruginosa may more quickly proliferate than M.flos-aquae through increased negative charges,bEPS contents.growth.and tryptophan-like substance contents at certain light intensities.展开更多
Two parallel membrane bioreactors （MBRs） were operated under different calcium dosages （168.5, 27 mg/L） to gain a better understanding of the mechanism of retarding membrane fouling by adding calcium. The results ...Two parallel membrane bioreactors （MBRs） were operated under different calcium dosages （168.5, 27 mg/L） to gain a better understanding of the mechanism of retarding membrane fouling by adding calcium. The results showed that the particle size of sludge flocs increased and the particle size distribution tended to be narrow at the optimum dosage （168.5 mg/L）. Calcium was effective in decreasing loosely bound extracellular polymeric substances （LB-EPS） in microbial flocs and soluble microbial products （SMP） in the supernatant at the dosage of 168.5 mg/L by strengthening the neutralization and bridging of EPS with flocs. Furthermore, the amount of CODs and CODc decreased in both the mixed liquor and the fouling cake layer on the membrane surface. In order to compare the filtration characteristics of cake layers from the MBRs with the two calcium dosages, the specific cake resistance and the compressibility coefficient were measured. The specific cake resistance from the MBR with optimum dosage （168.5 mg/L） was distinctly lower than that with low dosage （27 mg/L）. The compressibility coefficient of the cake layers under two dosages were respectively attained as 0.65, 0.91. Scanning electron microscopy （SEM） and three-dimensional confocal scanning laser microscope analysis （CLSM） images were utilized to observe the gel layer directly.展开更多
基金supported by the Natural Scientific Foundation of China (Nos.40825004,40971252,41301544)the Water Pollution Control and Management Project (No.2012ZX07101-010)the Shandong Province Natural Science Foundation of China (No.ZR2012DQ003)
文摘Preliminary characterization of bound extracellular polymeric substances（bEPS） of cyanobacteria is crucial to obtain a better understanding of the formation mechanism of cyanobacterial bloom. However,the characterization of bEPS can be affected by extraction methods. Five sets（including the control） of bEPS from Microcystis extracted by different methods were characterized using three-dimensional excitation and emission matrix（3DEEM） fluorescence spectroscopy combined chemical spectrophotometry; and the characterization results of bEPS samples were further compared. The agents used for extraction were NaOH,pure water and phosphate buffered saline（PBS） containing cationic exchange resins,and hot water. Extraction methods affected the fluorescence signals and intensities in the bEPS. Five fluorescence peaks were observed in the excitation and emission matrix fluorescence spectra of bEPS samples. Two peaks（peaks T1 and T2） present in all extractions were identified as protein-like fluorophores,two（peaks A and C） as humic-like fluorophores,and one（peak E） as a fulvic-like substance.Among these substances,the humic-like and fulvic-like fluorescences were only seen in the bEPS extracted with hot water. Also,NaOH solution extraction could result in strong fluorescence intensities compared to the other extraction methods. It was suggested that NaOH at pH 10.0 was the most appropriate method to extract bEPS from Microcystis. In addition,dialysis could affect the yields and characteristics of extracted bEPS during the determination process. These results will help us to explore the issues of cyanobacterial blooms.
基金Supported by the National Natural Science Foundation of China(No.31800457)the Natural Science Foundation of Hubei(No.2016CFB355)。
文摘Bound extracellular polymeric substances(bEPS)play an important role in the proliferation of Microcystis.However,the understanding of bEPS characterization remains limited.In this study,threedimensional fluorescence excitation-emission matrix(3D-EEM)spectroscopy and zeta potentiometer were used to characterize the loosely bound EPS(LB-EP S)and tightly bound EPS(TB-EPS)from two dominant Microcystis morphospecies from Taihu Lake(China)at different light intensities.Physiochemical analysis showed that the growth and TB-EPS or bEPS contents in Microcystis aeruginosa were higher than those in Microcystisfl os-aquae at each light intensity.The 3D-EEM contour demonstrated that the intensities of peak B(tryptophan-like substances)in the TB-EPS from M.aeruginosa were stronger than those from M.flosaquae when the light intensity was higher than 10μE/(m^(2)·s).Zeta potential analysis showed that the absolute values of the zeta potential of TB-EPS in the two species both increased with rising light intensity,except those of TB-EPS in M.aeruginosa at 105μE/(m^(2)·s).Moreover,the absolute values of the zeta potential of M.aeruginosa were higher than tho se of M.flos-aquae at each light intensity.All these re sults indicated that M.aeruginosa may more quickly proliferate than M.flos-aquae through increased negative charges,bEPS contents.growth.and tryptophan-like substance contents at certain light intensities.
基金supported by the National Natural Science Foundation of China (No. 50578024)
文摘Two parallel membrane bioreactors （MBRs） were operated under different calcium dosages （168.5, 27 mg/L） to gain a better understanding of the mechanism of retarding membrane fouling by adding calcium. The results showed that the particle size of sludge flocs increased and the particle size distribution tended to be narrow at the optimum dosage （168.5 mg/L）. Calcium was effective in decreasing loosely bound extracellular polymeric substances （LB-EPS） in microbial flocs and soluble microbial products （SMP） in the supernatant at the dosage of 168.5 mg/L by strengthening the neutralization and bridging of EPS with flocs. Furthermore, the amount of CODs and CODc decreased in both the mixed liquor and the fouling cake layer on the membrane surface. In order to compare the filtration characteristics of cake layers from the MBRs with the two calcium dosages, the specific cake resistance and the compressibility coefficient were measured. The specific cake resistance from the MBR with optimum dosage （168.5 mg/L） was distinctly lower than that with low dosage （27 mg/L）. The compressibility coefficient of the cake layers under two dosages were respectively attained as 0.65, 0.91. Scanning electron microscopy （SEM） and three-dimensional confocal scanning laser microscope analysis （CLSM） images were utilized to observe the gel layer directly.
