microcystin-LR In Water Research Articles

Efficient simultaneous removal of phosphate and microcystin-LR in water using a novel g-C3N4/calcite composite under dark-visible light cycles

Harmful algal blooms (HABs) associated with the abundant presence of phosphorus and microcystin in natural waters have raised a growing global concern. In this study, an adsorption-photocatalysis strategy was developed using a novel g-C3N4/calcite composite for efficient simultaneous removal of phosphate and microcystin-LR in water under dark-visible light cycles for the first time. The appropriate introduction of calcite into g-C3N4 (i.e., g-C3N4/calcite-1) was efficient in both phosphate adsorption (>78.5 %) and microcystin-LR degradation (>84.3 %) under a dark-visible light cycle of 3:3h at an optimal dosage of 100 mg/L in waters (pH 5–9 and temperature 10–40 °C). The simultaneous removal mechanisms proposed that g-C3N4/calcite-1 adsorbed phosphate via adsorption and precipitation with surface Ca2+, and degraded microcystin-LR via oxidation by photogenerated reactive species (mainly h+ and •OH). The material characterizations and density functional theory (DFT) calculations revealed that the combination of g-C3N4 and calcite could not only change the electric field distributions of calcite and optimize the charge transfer during adsorption to improve its adsorption capacity towards phosphate, but also narrow the band gaps of g-C3N4, promote the electron-hole separation and lower the first-step reaction barrier in oxygen reduction pathway during photocatalysis to enhance its visible-light photocatalytic activity towards microcystin-LR. Collectively, these findings are believed to offer valuable insights on the green material design for water environmental remediation and the underlying mechanism elucidation for simultaneous removal of phosphorus and microcystin in water to achieve effective comprehensive management of HABs.

Simultaneous inactivation of Microcystis aeruginosa and degradation of microcystin-LR in water by activation of periodate with sunlight

Harmful algal blooms pose tremendous threats to ecological safety and human health. In this study, simulated solar light (SSL) irradiation was used to activate periodate (PI) for the inactivation of Microcystis aeruginosa and degradation of microcystin-LR (MC-LR). We found that PI-SSL system could effectively inactivate 5 × 106 cells·mL−1 algal cells below the limit of detection within 180 min. ·OH and iodine (IO3· and IO4·) radicals generated in PI-SSL system could rupture cell membranes, releasing intracellular substances including MC-LR into the reaction system. However, the released MC-LR could be degraded into non-toxic small molecules via hydroxylation and ring cleavage processes in PI-SSL system, reducing their environmental risks. High algae inactivation performance of PI-SSL system in solution with a wide pH range (3–9), with the coexisting anions (Cl−, NO3− and SO42−) and the copresence of natural organic matters (humic acid and fulvic acid), real water (lake water and river water), as well as in continuous-flow reactor (14 h) were also achieved. In addition, under natural sunlight irradiation, effective algae inactivation could also be achieved in an enlarged reactor (1 L). Overall, our study showed that PI-SSL system could avoid the inference by the background substances and could be employed as a feasible technique to treat algal bloom water.

Coupling physiochemical adsorption with biodegradation for enhanced removal of microcystin-LR in water

To innovate the design of water treatment technology for algal toxin removal, this research investigated the mechanisms of cyanotoxin microcystin-LR (MC-LR) removal by a coupled adsorption-biodegradation. Eight types of woody carbonaceous adsorbents with and without Sphingopyxis sp. m6, a MC-LR degrading bacterium, were tested for MC-LR removal in water. All adsorbents showed good adsorption capability, removing 40 % to almost 100 % of the MC-LR (4.5 mg/L) within 48 h in batch experiments. Adding Sphingopyxis sp. m6 continuously promoted MC-LR biological removal, and successfully broke the barrier of adsorption capacity of tested adsorbents, removing >90 % of the MC-LR in most of the coupled adsorption-biodegradation tests, especially for those adsorbents had low physiochemical adsorption capacity. Variance partitioning analysis indicated that mesopore was the dominant contributor to adsorption capacity of MC-LR in pure adsorption treatments, which acted synergistically with electrical conductivity, polarity and total functional groups on the absorbent. Pore structure was the key factor beneficial for the growth of Sphingopyxis sp. m6 (51% contribution) and subsequent MC-LR biological removal rate (80 % contribution). Overall, pinewood-based carbonaceous adsorbents (especially pinewood activated carbon) exhibited the highest adsorption capacity towards MC-LR and provided the most favorable conditions for biological removal of MC-LR, largely because of their high mesopore volume, total functional groups and electric conductivity. The research outcomes not only deepened the quantitative understanding of mechanisms for MC-LR removal by the coupled process, but also provided theoretical basis for future materials' selection and modification during the practical application of coupled process.

Light-Initiated Imprinted Membrane-Based Biomimetic SERS Sensor toward Selective Detection of Trace MC-LR.

Microcystin-LR (MC-LR) is a severe threat to human and animal health; thus, monitoring it in the environment is essential, especially in water quality protections. Herein, in this work, we synthesize PVDF/CNT/Ag molecular imprinted membranes (PCA-MIMs) via an innovative combination of surface-enhanced Raman spectroscopy (SERS) detection, membrane separation, and molecular-imprinted technique toward the analysis of MC-LR in water. In particular, a light-initiated imprint is employed to protect the chemical structure of the MC-LR molecules. Furthermore, in order to ensure the detection sensitivity, the SERS substrates are combined with the membrane via the assistance of magnetism. The effect of synthesis conditions on the SERS sensitivity was investigated in detail. It is demonstrated from the characteristic results that the PCA-MIMs present high sensitivity to the MC-LR molecules with excellent selectivity against the interfere molecules. Results clearly show that the as-prepared PCA-MIMs hold great potential applications to detect trace MC-LR for the protection of water quality.

Analyzing MC-LR distribution characteristics in natural lakes by a novel fluorescence technology

The death of aquatic and terrestrial organisms caused by cyanobacterial blooms has been a topic of considerable concern since the 19th century. Microcystin-LR (MC-LR) produced by cyanobacterial blooms threaten natural ecosystems and human health. Therefore, establishing an effective monitoring and early warning system to detect MC-LR in water bodies is crucial. However, rapidly and intuitively assessing the distribution traits of MC-LR in lakes is a challenging task due to the complexities and expenses associated with conventional detection methods. To overcome these technical limitations, we introduce a novel and effective method for evaluating the distribution of MC-LR in lakes. This method is achieved by using a fluorescence probe (BAD) technology, marking the first application of this technology in evaluating the distribution of MC-LR in natural lake environments. The probe BAD is endowed with unique functions through clever functionalization modification. Experimental results exhibit that BAD has different fluorescence signals at various lake sampling points. The correlation analysis of fluorescence data and physicochemical indicators determines that the fluorescence data of the probe exhibit good correlation with MC-LR, implying that BAD is capable of detecting MC-LR in lakes. Moreover, the introduction of fluorescence technology to achieve the intuitive distribution of MC-LR in the entire plateau lake. This study provides a new method for evaluating the distribution of MC-LR in plateau lakes. It opens a new avenue for exploring the relationship between cyanobacterial blooms and MC-LR in natural waters.

Recent Progress and Applications of Thermal Lens Spectrometry and Photothermal Beam Deflection Techniques in Environmental Sensing.

This paper presents recent development and applications of thermal lens microscopy (TLM) and beam deflection spectrometry (BDS) for the analysis of water samples and sea ice. Coupling of TLM detection to a microfluidic system for flow injection analysis (μFIA) enables the detection of microcystin-LR in waters with a four samples/min throughput (in triplicate injections) and provides an LOD of 0.08 µg/L which is 12-times lower than the MCL for microcystin-LR in water. μFIA-TLM was also applied for the determination of total Fe and Fe(II) in 3 µL samples of synthetic cloudwater. The LODs were found to be 100 nM for Fe(II) and 70 nM for total Fe. The application of µFIA-TLM for the determination of ammonium in water resulted in an LOD of 2.3 µM for injection of a 5 µL sample and TLM detection in a 100 µm deep microfluidic channel. For the determination of iron species in sea ice, the BDS was coupled to a diffusive gradient in the thin film technique (DGT). The 2D distribution of Fe(II) and total Fe on DGT gels provided by the BDS (LOD of 50 nM) reflected the distribution of Fe species in sea ice put in contact with DGT gels.

Aggregation-induced emission luminogens-encoded microspheres preparation and flow-through immunoaffinity chromatographic assay development for microcystin-LR analysis

Despite decades of efforts, we are faced with the daunting task of on-site ultratrace environmental toxins detecting, especially the microcystins caused by water bloom. In this work, a novel fluorescent microsphere-based flow-through immunoaffinity chromatographic assay has been designed for detecting ultratrace microcystin-LR in water and aquatic products. The aggregation-induced emission luminogens were encapsulated into fluorescent microspheres to ensure microcystin-LR quantitation with a whole analytical time of less than 30 min. Furthermore, the colorimetric images were captured and quantitatively analyzed, which offered a limit of detection at 0.217 pg/mL and a limit of quantitation at 0.362 pg/mL in water and aquatic muscle samples. The developed immunoassays provide average recovery ranging from 79.1 % to 95.7 %, with relative standard deviations less than 13.4 %. Thus, the validated flow-through immunoaffinity chromatographic assay is an easy-to-use alternative for on-site screening of microcystin-LR in water and aquatic samples at picogram levels.

Rapid detoxification of Microcystin-LR by selective catalytic hydrogenation of the Adda moiety using TiO2-supported Pd catalysts

The hepatotoxicity of Microcystin-LR (MC-LR) is mainly caused by its Adda moiety. In this study, we used TiO2-supported Pd catalysts to selectively hydrogenate the CC bonds in the Adda moiety, achieving rapid detoxification of MC-LR in water under ambient conditions. MC-LR was removed within 5 min by catalytic hydrogenation on Pd(1.0)/TiO2 with a catalyst dosage normalized rate constant of 1.3 × 10−2 L mgcat−1 min−1, significantly more efficient than other catalytic treatment methods. The reactions proceeded in a highly selective manner towards catalytic hydrogenation at the CC bond of the Mdha moiety and subsequently the conjugated double bond of the Adda moiety, yielding two intermediates and one final product. Upon catalytic hydrogenation for 30 min on Pd(0.07)/TiO2, the toxicity of MC-LR (assessed by protein phosphatase 2A activity assay) drastically decreased by 90.8%, demonstrating effective detoxification. The influence of catalyst support, Pd content, initial MC-LR concentration, reaction pH, and catalytic stability were examined. Surface adsorption and the cationic Pd played a crucial role in the reaction kinetics. Our results suggest that catalytic hydrogenation is a highly effective and safe strategy for detoxifying MC-LR by selective reactions.

Aptamer-functionalized metal-organic framework-based electrospun nanofibrous composite coating fiber for specific recognition of ultratrace microcystin in water

A novel aptamer@AuNPs@UiO-66-NH2 electrospun nanofibrous coating fiber for specific recognition of microcystin-LR (MC-LR) was proposed by using electrospinning, metal-organic frameworks (MOF) seed growth and AuNPs bridging aptamer strategies. Characterization of morphology, structure and stability of the obtained affinity nanofibrous coating fiber were investigated. High loading of MOFs and aptamers on the nanofibrous fiber were achieved and successfully applied for accurate identification of MC-LR by solid-phase microextraction (SPME) coupled with LC-MS. Highly specific recognition of MC-LR with little interference of analogs was achieved with extremely low LOD (0.004 ng/mL), good precision (CV% < 11.0%) and low relative error (RE% = −1.5% to −10.0%), which was rather better than that of the traditional SPME or SPE protocols. Satisfactory recoveries of MC-LR were obtained in the range of 92.0–96.8% (n = 3) in fortified tap water, raw pond water and river water samples. This work revealed an attractive alternative access to specific recognition and super-sensitive analysis of MC-LR in water.

Thermally enhanced adsorption and persulfate oxidation-driven regeneration on FeCl3-activated biochar for removal of microcystin-LR in water

In this study, a cyclic process of adsorption and persulfate (PS) oxidation-driven regeneration using FeCl3-activated biochar (FA-BC) was suggested as a novel remediation process to remove microcystin-LR (MC-LR) from water. For enhancing overall treatment efficiency and cost effectiveness, the impacts of temperature on adsorption and PS oxidation-driven regeneration were investigated. The increase of temperature resulted in the increase of MC-LR adsorption rate on FA-BC due to the enhanced MC-LR diffusivity in water. Moreover, the MC-LR oxidation and PS reaction rates during the PS regeneration on FA-BC were remarkably improved by factors of 3.4 and 3.5 with increasing temperature from 20 °C to 50 °C. Both diffusion and desorption of MC-LR from FA-BC were thought to be the key factors for controlling the MC-LR oxidation rate during the PS regeneration of MC-LR. In addition, the decrease of pH (from 10 to 4) and increase of PS concentration (from 100 to 400 mg/L) enhanced the regeneration efficiency for MC-LR-spent FA-BC. The four cycles of adsorption-PS regeneration (200 mg/L PS, pH 6, and 50 °C) resulted in 92.81% regeneration efficiency in DI water and 82.89% in lake water. However, the four cycles of adsorption-PS regeneration led to the reduction of surface area (from 835 to 413 m2/g), oxidation of carbon surface and slight reduction of Fe0 on FA-BC. In overall, the cyclic adsorption-PS regeneration at higher temperature could provide practical reuse of FA-BC for cost-effective treatment of aqueous MC-LR.

Light-driven breakdown of microcystin-LR in water: A critical review

• Light-driven oxidation technologies for removing microcystin-LR from water were reviewed. • Factors affecting the microcystin-LR degradation were probed. • Microcystin-LR was removed using photocatalysis/oxidation under real scenarios. • Conjugated dienes, double bonds, free carboxyl groups, and peptide ring were toxicity-induced structures. • Several new pathways of attacking peptide ring of microcystin-LR were introduced. Cyanobacterial algal blooms are ubiquitous around the globe and lead to severe cyanotoxin pollution, which poses a severe threat to the safety of drinking water. Microcystins (MCs), the monocyclic heptapeptides, are the most commonly occurring cyanotoxin, which consist of five D-amino acids and two variable L-amino acids. There exist over 100 MC variants, and microcystin-leucine arginine (MC-LR) is one of the most hazardous and prevalent variants. This review comprehensively discussed the status quo of investigations light-driven oxidation technology for degradation of MC-LR, including photolysis, heterogenous photocatalysis and homogeneous oxidation that are driven by UV, visible light and solar light (main information of homogeneous oxidation are shown in Supplementary materials). The effects of key parameters on these systems are critically clarified, including light wavelength, photocatalyst/oxidant concentration, initial MC-LR concentration, pH values, and coexisting organic or inorganic matter. An increasing number of studies are conducted on real water matrix at toxin concentrations and pH values that are similar to water contaminated by cyanobacterial algal blooms. However, very few studies have investigated the mineralization and detoxification of treated water, and little is known about the fragments of MC-LR that are responsible for its toxicity. Thereafter, reaction mechanism, ecotoxicological effects and operational costs of the MC-LR photodegradation process in all systems are also comprehensively elucidated. This paper will help to better understand the MC-LR decomposition process and provide improved perspectives for future research in this field.

A new method based on diffusive gradients in thin films for in situ monitoring microcystin-LR in waters

The passive sampling method of diffusive gradients in thin-films (DGT) was developed to provide a quantitative and time-integrated measurement of microcystin-LR (MC-LR) in waters. The DGT method in this study used HLB (hydrophilic-lipophilic-balanced) material as a binding agent, and methanol as an eluent. The diffusion coefficient of MC-LR was 5.01 × 10−6 cm2 s−1 at 25 °C in 0.45 mm thick diffusion layer. This DGT method had a binding capacity of 4.24 μg per binding gel disk (3.14 cm2), ensuring sufficient capacity to measure MC-LR in most water matrices. The detection limit of HLB DGT was 0.48 ng L−1. DGT coupled to analysis by HPLC appears to be an accurate method for MC-LR monitoring. Comparison of DGT measurements for MC-LR in water and a conventional active sampling method showed little difference. This study demonstrates that HLB-based DGT is a useful tool for in situ monitoring of MC-LR in fresh waters.

Fluorescent enzyme-linked immunoassay based on silane-doped carbon dots for sensitive detection of microcystin-LR in water and crucian samples

In this work, a fluorescent nanoparticles labeling-free fluorescence enzyme-linked immunoassay (FELISA) has been established for the ultrasensitive detection of microcystin-LR (MC-LR) in water and fish samples. Polyclonal antibody against MC-LR was labeled with horseradish peroxidase (HRP) and used as signal probe for binding with analyte in sample or for coating antigen. After washing of the unbound antibody, the substrate system (2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS)/H2O2) was added. The oxidation product of ABTS (ox-ABTS) catalyzed by HRP effectively caused the fluorescence quenching of subsequently added silane-doped carbon dots (Si-CDs), and the change in fluorescence intensity of Si-CDs was used to realize the quantitative detection of MC-LR. Under the optimum conditions, the Si-CDs based FELISA method showed a good linear relationship from 0.001 to 3.20 μg L−1 (R2 = 0.994) and provided a low detection limit of 0.6 ng L-1, which was approximately 30-fold lower than that of traditional indirect competitive ELISA. Average recovery values from 79.9% to 109.2% was obtained from spiked water and crucian samples, suggesting its potential application on the monitoring of MR-LR at a trace level.

Catalytic hydrolysis of microcystin-LR peptides on the surface of naturally occurring minerals

There are increasing concerns about detoxification of microcystin-LR (MC-LR) over the past few decades. Nevertheless, the removal of MC-LR in water by hydrolysis has not been addressed yet. The hydrolysis efficiencies of MC-LR by six natural minerals were investigated in the present study. Limonite displayed the highest activity among the screened six minerals, which is in accordance with the highest specific surface area (17.8 m2/g) and surface acidity. The hydrolysis of MC-LR was catalyzed by Lewis acid sites on limonite surface. The effects of temperature, pH reaction time and illumination on MC-LR hydrolysis catalyzed by limonite were then investigated. As expected, the high temperature, the addition of either acid or base and long reaction time could enhance the reaction rate, but UV light irradiation had little influence. These results give the indication that naturally occurring minerals can promote the hydrolysis of MC-LR, which gives a more universal view about the natural degradation of microcystins and could lead to more accurate predictions of the duration of microcystin toxicity in environment.

Degradation and mechanism of microcystin-LR by PbCrO4 nanorods driven by visible light

This work focuses on the photocatalytic removal of recalcitrant organic pollutants in water treatment. Based on facile precipitation reaction, we fabricated a photocatalyst (PbCrO4) in single crystals that present evident response to visible light and employed the catalyst in the photocatalytic decomposition of microcystin-LR (MC-LR). In the degradation test using the nanorods with prepared PbCrO4 photocatalyst, a 100% removal efficiency (27 min reaction) and a kinetics constant of 0.1356 min−1 were achieved. Such a high performance of PbCrO4 in photocatalytic conversion of MC-LR was ascribed to its high carrier separation efficiency, positive valence band (VB) position, and good delocalization of VB and conduction band (CB). The test of electron spin-resonance resonance (ESR) demonstrated that excessive free OH radicals were produced during the PbCrO4 photocatalysis of MC-LR. The density functional theory (DFT) and LC/MS/MS technology were employed to ascertain the intermediates during the MC-LR photocatalytic degradation. The major intermediates were resulted from the attack of hydroxyl radicals to the ADDA side chains of MC-LR structure. This study provides a proof-of-concept strategy to develop effective photocatalysts to efficiently produce OH radicals for the visible-light induced photocatalytic degradation of MC-LR in water.

Phosphorescent immunosensor for simple and sensitive detection of microcystin-LR in water.

A simple and sensitive Mn–ZnS quantum dot room-temperature phosphorescent immunosensor for detecting microcystin-LR was developed. This sensor adopted antigens and antibodies as recognition units and used Mn–ZnS RTP QDs as sensing materials to specifically bind with MC-LR. The structurally specific binding between the microcystin-LR antibody and MC-LR led to the aggregation of antibody-crosslinked QDs, and then the electrons of QDs would be transferred to the complex, leading to the phosphorescence quenching of QDs. The microcystin-LR antigen–antibody specific binding site was first analyzed. This phosphorescent immunosensor rapidly and sensitively detected microcystin-LR, with linear ranges of 0.2–1.5 μg L−1 and 1.5–20 μg L−1 and a detection limit of up to 0.024 μg L−1. Meanwhile, coexisting pollutants of microcystin-LR in water did not significantly interfere with microcystin-LR detection. The new sensor was applied to detect real water samples and showed high sensitivity and selectivity.

MATERIALS FOR THE SUBSTANTIATION OF HYGIENIC STANDARD OF MICROCYSTIN-LR IN WATER OF WATER OBJECTS

Introduction. The growth of the anthropogenic pollution of water bodies and the regulation of river flow has led to an almost universal intensification of eutrophication of water bodies, which contributes to the mass development (“blooming “) in the summer cyanobacteria - blue-green algae. The main danger of “ blooming “ is the ability of cyanobacteria to produce toxins to adversely affect human health, among which hepatotoxin microcystin-LR takes the first place in prevalence and toxicity. To date, microcystin-LR in drinking water is regulated by WHO and 22 States, but in Russia, microcystin-LR in water is not standardized. The purpose of this work is to substantiate the MAC of microcystin-LR in water of water bodies and drinking water of the Russian Federation. Material and methods. The data of the world practice of the toxicity assessment of microcystin-LR, including the acute and chronic effects of microcystin-LR on animals and humans in natural conditions; the results of the study of acute, subacute and chronic toxic effects, effects on reproductive function, mutagenic, genotoxic and carcinogenic effects in experiments on laboratory animals were analyzed. The methodology of substantiation and harmonization of hygienic standards of substances in water was used. Results. Analysis of the information about the toxic effect of microcystin-LR, the experience of WHO and 22 countries on the regulation of its permissible content in water, as well as domestic experience of justification and harmonization of hygienic standards makes it possible to recommend the MAC microcystin-LR in water of water bodies and drinking water at the level of 0.001 mg/l marked “k” (carcinogen), 1st hazard class, limiting harmfulness index - sanitary-toxicological. Discussion. The results of the study showed that to justify the MAC of microcystin-LR in water, one index of harmfulness is sufficient - sanitary-toxicological, the study of the effect on organoleptic and general sanitary indices is not advisable because of the specific properties of the toxin. Conclusion. In the conditions of non-decreasing pollution of water bodies with cyanotoxins of blue-green algae, the introduction of MAC microcystin-LR will be important for the prevention of its adverse effects on public health.

A competitive microcystin-LR immunosensor based on Au NPs@metal-organic framework (MIL-101)

An electrochemical immunosensor was developed for ultrasensitive detection of microcystin-LR in water. MIL-101, a porous metal-organic frameworks (MOFs) material based on trivalent chromium skeleton were synthesized by hydrothermal synthesis method, and loaded with Au nanoparticles (Au NPs) to prepare Au NPs@MIL-101 composite materials which were used as a marker to label anti microcystin-LR (Anti-MC-LR). The composite materials have strong catalytic properties to the oxidation of ascorbic acid. Anti-MC-LR was immobilized on glassy carbon electrode surface using electrodeposition graphene oxide (GO) as an immobilization matrix to construct a competitive microcystin-LR immunosensor. The electrochemical immunosensor display linear relationship in the range of 0.05 ng/mL−75 μg/mL with linear correlation coefficient of 0.9951 and detection limit of 0.02 ng/mL (S/N = 3). This sensor was used to detect microcystin-LR in the water sample. The recovery was 102.43%, which is satisfied. The good testing results indicate the sensor has a great prospect in practical application.

Removal of Microcystin-LR by a Novel Native Effective Bacterial Community Designated as YFMCD4 Isolated from Lake Taihu.

Microcystin-LR (MC-LR) is the most toxic and frequently detected monocyclic heptapeptide hepatotoxin produced by cyanobacteria, which poses a great threat to the natural ecosystem and public health. It is very important to seek environment-friendly and cost-efficient methods to remove MC-LR in water. In this study, the MC-degrading capacities of a novel indigenous bacterial community designated as YFMCD4 and the influence of environmental factors including various temperatures, MC concentrations and pH on the MC-degrading activities were investigated utilizing high-performance liquid chromatography (HPLC). In addition, the MC-degrading mechanism of YFMCD4 was also studied using HPLC coupled with a mass spectrometry equipped with electrospray ionization interface (HPLC-ESI-MS). The data showed MC-LR was completely removed at the maximum rate of 0.5 µg/(mL·h) under the optimal condition by YFMCD4. Two pure bacterial strains Alcaligenes faecalis and Stenotrophomonas acidaminiohila were isolated from YFMCD4 degraded MC-LR at a slower rate. The MC-degrading rates of YFMCD4 were significantly affected by different temperatures, pH and MC-LR concentrations. Two intermediates of a tetrapeptide and Adda appeared in the degradation process. These results illustrate that the novel YFMCD4 is one of the highest effective MC-degrading bacterial community, which can completely remove MC-LR and possesses a significant potential to treat water bodies contaminated by MC-LR.

Solar photo-Fenton treatment of microcystin-LR in aqueous environment: Transformation products and toxicity in different water matrices

Transformation products and toxicity patterns of microcystin-LR (MC-LR), a common cyanotoxin in freshwaters, during degradation by solar photo-Fenton process were studied in the absence and presence of two major water components, namely fulvic acid and alkalinity. The transformation products m/z 795, 835, 515/1030 and 532 can be formed through attack of OH on the conjugated carbon double bonds of Adda. Transformation products with m/z 1010, 966 and 513 can be generated through the attack of OH on the methoxy group of Adda. The transformation products m/z 783, 508 and 1012 can be originated from the attack of OH on the cyclic structure of MC-LR. Transformation products (m/z 522, 1028, 1012, 1046 and 514) formed after hydroxylation of the aromatic ring with OH were also identified in this study. The toxicity study revealed that fulvic acid and alkalinity strongly influence the toxicity profiles of solar photo-Fenton treated MC-LR. Fulvic acid enhanced the detoxification whereas low level total alkalinity (1.8 mg L−1 CaCO3) inhibited the detoxification of MC-LR by solar photo-Fenton process as assessed by protein phosphatase-1 (PP-1) inhibition assay. This work provides insights on the utility of solar photo-Fenton destruction of MC-LR in water based on transformation products and toxicity data.