A strain, USTB-05, isolated from Lake Dianchi, China, degraded the cyanobacterial toxin microcystin-RR （MC-RR） at the rate of 16.7 mg/L per day. Analysis of 16S rDNA sequence showed that the strain was Sphingopyxis ...A strain, USTB-05, isolated from Lake Dianchi, China, degraded the cyanobacterial toxin microcystin-RR （MC-RR） at the rate of 16.7 mg/L per day. Analysis of 16S rDNA sequence showed that the strain was Sphingopyxis sp. Enzymatic degradation pathways for MC-RR by Sphingopyxis sp. USTB-05 were identified. Adda-Arg peptide bond of MC-RR was cleaved and then a hydrogen and a hydroxyl were combined onto the NH2 group of Adda and the carboxyl group of arginine to form a linear molecule as intermediate product within the first few hours. Then, through dehydration reaction, two hydrogen of amino group on arginine reacted with adjacent hydroxyl on carbon to form a linear MC-RR with two small peptide rings as the final product after 24 hr. These biodegradation pathways were different from those reported for other strains, implying that MC-RR may undergo different transformations and different products were formed due to various bacteria in natural lakes and reservoirs.展开更多
The experiments were performed to investigate the degradation of microcystins in order to assess the effectiveness and feasibility of UV/H2O2 system for the disinfection of water polluted by microcystins. The influenc...The experiments were performed to investigate the degradation of microcystins in order to assess the effectiveness and feasibility of UV/H2O2 system for the disinfection of water polluted by microcystins. The influence factors such as H2O2, pH and UV light intensities were investigated respectively. Degradation of microcystin-RR （MC-RR） could be fitted by either the pseudo-first-order or second-order rate equations. This homogenous system could significantly enhance the degradation rate due to the synergetic effect between UV and H2O2. The degradation mainly followed the mechanism of direct photolysis and .OH oxidation reactions. Experimental results showed that 94.83% of MC-RR was removed under optimal experimental conditions and the UV/H2O2 system provided an alternative to promote the removal of microcystins in drinking water supplies.展开更多
A promising bacterial strain for the biodegradation of Microcystins(MCs)was isolated from Dianchi lake in China and identified as Sphingopyxis sp.USTB-05 by the analysis of 16s rDNA.Initial MC-RR of 42.3 mg·L -1 ...A promising bacterial strain for the biodegradation of Microcystins(MCs)was isolated from Dianchi lake in China and identified as Sphingopyxis sp.USTB-05 by the analysis of 16s rDNA.Initial MC-RR of 42.3 mg·L -1 was completely degraded by USTB-05 within 36 h,which was a relatively high biodegradation rate of MC-RR.With the cell-free extract(CE)of Sphingopyxis sp.USTB-05,MC-RR was biodegraded at a more rapid biodegradation rate compared with its strain,so that initial MC-RR of 42.3 mg·L -1 was completely biodegraded within 10 h.During the bio-reaction of MC-RR catalyzed by CE,two intermediate metabolites and a dead-end product of MC-RR were observed on HPLC profiles and all of them had similar scanning profiles in the wavelength from 200 to 300 nm,indicating that the group of Adda in all products of MC-RR remained intact.展开更多
Due to the potent hepatotoxicity and tumor-promoting activity of microcystins, a successful removal of these toxins during drinking water treatment processes is of increasing concern. The oxidation kinetics of MC-RR b...Due to the potent hepatotoxicity and tumor-promoting activity of microcystins, a successful removal of these toxins during drinking water treatment processes is of increasing concern. The oxidation kinetics of MC-RR by chlorine dioxide (ClO2) was studied with HPLC and characterization of the reaction products was performed with UV-spectrometry, TOC and LC-MS. Our experimental results show that the oxidation process is a second order overall and a first order with respect to ClO2 and MC-RR. The activation energy of MC-RR degradation by ClO2 is 53.07 kJ/mol. The rate constant k of the action can be increased by in- creasing temperature and decreasing pH value and ranged from 6.11×102 L/(mol·min) to 5.29×102 L/(mol·min) at pH from 3.44 to 10.41 at 10 ℃. Reaction products were determined to be organic and volatile, because they could be almost removed from aqueous solution by heating for 15 min at 60 ℃ . In addition, the main oxidation products have m/z values of 1072 and are identified as di- hydroxy isomers of MC-RR.展开更多
This is the first report of the algal toxins of water bloom in Guanting Reservoir of Beijing. The algal compositions and one family of their toxins-microcystins were investigated. The dominant species in the blooms fo...This is the first report of the algal toxins of water bloom in Guanting Reservoir of Beijing. The algal compositions and one family of their toxins-microcystins were investigated. The dominant species in the blooms found in September of 2003 were Microcystis, whose ratio to the number of total algal cells reach 97.2%. The specific species of the microcystis in the bloom included microcystis aeruginosa(52.7%), microcystis wesenbergii(36.2%) and Microcystis pseudofilamentasa(8.3%). The qualitative analysis by HPLC shows that at least five microcystins were contained in the scum of the blooms. The major microcystins were microcystin-RR and microcystin-LR. The quantitative analysis by HPLC indicates that the blooms contained microcystin-RR 1^69 mg/g and microcystin-LR {1.44 mg/g} dried sample. The other three microcystins would be studied later.展开更多
基金supported by the Chinese National Key Project for Basic Research (No.2008CB418105)the National Natural Science Foundation of China(No.20621703,20477050)the Important-Direction-Project funded by the Chinese Academy of Sciences
文摘A strain, USTB-05, isolated from Lake Dianchi, China, degraded the cyanobacterial toxin microcystin-RR （MC-RR） at the rate of 16.7 mg/L per day. Analysis of 16S rDNA sequence showed that the strain was Sphingopyxis sp. Enzymatic degradation pathways for MC-RR by Sphingopyxis sp. USTB-05 were identified. Adda-Arg peptide bond of MC-RR was cleaved and then a hydrogen and a hydroxyl were combined onto the NH2 group of Adda and the carboxyl group of arginine to form a linear molecule as intermediate product within the first few hours. Then, through dehydration reaction, two hydrogen of amino group on arginine reacted with adjacent hydroxyl on carbon to form a linear MC-RR with two small peptide rings as the final product after 24 hr. These biodegradation pathways were different from those reported for other strains, implying that MC-RR may undergo different transformations and different products were formed due to various bacteria in natural lakes and reservoirs.
文摘The experiments were performed to investigate the degradation of microcystins in order to assess the effectiveness and feasibility of UV/H2O2 system for the disinfection of water polluted by microcystins. The influence factors such as H2O2, pH and UV light intensities were investigated respectively. Degradation of microcystin-RR （MC-RR） could be fitted by either the pseudo-first-order or second-order rate equations. This homogenous system could significantly enhance the degradation rate due to the synergetic effect between UV and H2O2. The degradation mainly followed the mechanism of direct photolysis and .OH oxidation reactions. Experimental results showed that 94.83% of MC-RR was removed under optimal experimental conditions and the UV/H2O2 system provided an alternative to promote the removal of microcystins in drinking water supplies.
基金Supported by the State Key Development Program for Basic Research of China（2008CB418105） the National Natural Science Foundation of China（203777008 20621703）+1 种基金 the State Key Joint Laboratory of Environment Simulation and Pollution Control（09K08ESPCT） the Educational Committee of Beijing
文摘A promising bacterial strain for the biodegradation of Microcystins(MCs)was isolated from Dianchi lake in China and identified as Sphingopyxis sp.USTB-05 by the analysis of 16s rDNA.Initial MC-RR of 42.3 mg·L -1 was completely degraded by USTB-05 within 36 h,which was a relatively high biodegradation rate of MC-RR.With the cell-free extract(CE)of Sphingopyxis sp.USTB-05,MC-RR was biodegraded at a more rapid biodegradation rate compared with its strain,so that initial MC-RR of 42.3 mg·L -1 was completely biodegraded within 10 h.During the bio-reaction of MC-RR catalyzed by CE,two intermediate metabolites and a dead-end product of MC-RR were observed on HPLC profiles and all of them had similar scanning profiles in the wavelength from 200 to 300 nm,indicating that the group of Adda in all products of MC-RR remained intact.
基金Projects 50178022 supported by the National Natural Science Foundation of China2006AA06Z309 by the Hi-tech Research and Development Programof China
文摘Due to the potent hepatotoxicity and tumor-promoting activity of microcystins, a successful removal of these toxins during drinking water treatment processes is of increasing concern. The oxidation kinetics of MC-RR by chlorine dioxide (ClO2) was studied with HPLC and characterization of the reaction products was performed with UV-spectrometry, TOC and LC-MS. Our experimental results show that the oxidation process is a second order overall and a first order with respect to ClO2 and MC-RR. The activation energy of MC-RR degradation by ClO2 is 53.07 kJ/mol. The rate constant k of the action can be increased by in- creasing temperature and decreasing pH value and ranged from 6.11×102 L/(mol·min) to 5.29×102 L/(mol·min) at pH from 3.44 to 10.41 at 10 ℃. Reaction products were determined to be organic and volatile, because they could be almost removed from aqueous solution by heating for 15 min at 60 ℃ . In addition, the main oxidation products have m/z values of 1072 and are identified as di- hydroxy isomers of MC-RR.
文摘This is the first report of the algal toxins of water bloom in Guanting Reservoir of Beijing. The algal compositions and one family of their toxins-microcystins were investigated. The dominant species in the blooms found in September of 2003 were Microcystis, whose ratio to the number of total algal cells reach 97.2%. The specific species of the microcystis in the bloom included microcystis aeruginosa(52.7%), microcystis wesenbergii(36.2%) and Microcystis pseudofilamentasa(8.3%). The qualitative analysis by HPLC shows that at least five microcystins were contained in the scum of the blooms. The major microcystins were microcystin-RR and microcystin-LR. The quantitative analysis by HPLC indicates that the blooms contained microcystin-RR 1^69 mg/g and microcystin-LR {1.44 mg/g} dried sample. The other three microcystins would be studied later.
基金supported by the National Natural Science Foundation of China (21677086, 21407092, 21377067, 21577078)the Natural Science Foundation for Innovation Group of Hubei Province, China (2015CFA021)~~
