Heavy metal pollution in immobile and mobile components of lentic ecosystems-a review.

With growing population and urbanization, there is an increasing exploitation of natural resources, and this often results to environmental pollution. In this review, the levels of heavy metal in lentic compartments (water, sediment, fishes, and aquatic plants) over the past two decades (1997-2017) have been summarized to evaluate the current pollution status of this ecosystem. In all the compartments, the heavy metals dominated are zinc followed by iron. The major reason could be area mineralogy and lithogenic sources. Enormous quantity of metals like iron in estuarine sediment is a very natural incident due to the permanently reducing condition of organic substances. Contamination of cadmium, lead, and chromium was closely associated with anthropogenic origin. In addition, surrounding land use and atmospheric deposition could have been responsible for substantial pollution. The accumulation of heavy metals in fishes and aquatic plants is the result of time-dependent deposition in lentic ecosystems. Moreover, various potential risk assessment methods for heavy metals were discussed. This review concludes that natural phenomena dominate the accumulation of essential heavy metals in lentic ecosystems compared to anthropogenic sources. Amongst other recent reviews on heavy metals from other parts of the world, the present review is executed in such a way that it explains the presence of heavy metals not only in water environment, but also in the whole of the lentic system comprising sediment, fishes, and aquatic plants.

Rapid bioremediation of Alizarin Red S and Quinizarine Green SS dyes using Trichoderma lixii F21 mediated by biosorption and enzymatic processes.

In this study, a newly isolated ascomycete fungus Trichoderma lixii F21 was explored to bioremediate the polar [Alizarin Red S (ARS)] and non-polar [Quinizarine Green SS (QGSS)] anthraquinone dyes. The bioremediation of ARS and QGSS by T. lixii F21 was found to be 77.78 and 98.31 %, respectively, via biosorption and enzymatic processes within 7 days of incubation. The maximum biosorption (ARS = 33.7 % and QGSS = 74.7 %) and enzymatic biodegradation (ARS = 44.1 % and QGSS = 23.6 %) were observed at pH 4 and 27 °C in the presence of glucose and yeast extract. The laccase and catechol 1,2-dioxygenase produced by T. lixii F21 were involved in the molecular conversions of ARS and QGSS to phenolic and carboxylic acid compounds, without the formation of toxic aromatic amines. This study suggests that T. lixii F21 may be a good candidate for the bioremediation of industrial effluents contaminated with anthraquinone dyes.

Fabrication, characterization and application of laccase-nylon 6,6/Fe3+ composite nanofibrous membrane for 3,3'-dimethoxybenzidine detoxification.

In this study, laccase was immobilized on nylon 6,6/Fe3+ composite (NFC) nanofibrous membrane and used for the detoxification of 3,3'-dimethoxybenzidine (DMOB). The average size and tensile strength of the NFC membrane were found to be 60-80 nm (diameter) and 2.70 MPa, respectively. The FTIR results confirm that the amine (N-H) group of laccase was attached with Fe3+ particles and the carbonyl (C=O) group of NFC membrane via hydrogen bonding. The half-life of the laccase-NFC membrane storage stability was increased from 6 to 11 weeks and the reusability was significantly extended up to 43 cycles against ABTS oxidation. Enhanced electro-oxidation of DMOB by laccase was observed at 0.33 V and the catalytic current was found to be 30 µA. The DMOB-treated mouse fibroblast 3T3-L1 preadipocytes showed maximum (97 %) cell inhibition at 75 µM L-1 within 24 h. The cytotoxicity of DMOB was significantly decreased to 78 % after laccase treatment. This study suggests that laccase-NFC membrane might be a good candidate for emerging pollutant detoxification.

Phyto-synthesis of silver nanoparticles using Alternanthera tenella leaf extract: an effective inhibitor for the migration of human breast adenocarcinoma (MCF-7) cells.

In this study, phyto-synthesis of silver nanoparticles (AgNPs) was achieved using an aqueous leaf extract of Alternanthera tenella. The phytochemical screening results revealed that flavonoids are responsible for the AgNPs formation. The AgNPs were characterised using UV-visible spectrophotometer, field emission scanning microscopy/energy dispersive X-ray, transmission electron microscopy, fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction. The average size of the nanoparticles was found to be ≈48 nm. The EDX results show that strong signals were observed for the silver atoms. The strong band appearing at 1601-1595 cm(-1) correspond to C-C stretching vibration from dienes in FT-IR spectrum indicating the formation of AgNPs. Human breast adenocarcinoma (MCF-7) cells treated with various concentrations of AgNPs showed a dose-dependent increase in cell inhibition. The IC50 value of the AgNPs was calculated to be 42.5 µg mL(-1). The AgNPs showed a significant reduction in the migration of MCF-7 cells.

Synthesis of flexirubin-mediated silver nanoparticles using Chryseobacterium artocarpi CECT 8497 and investigation of its anticancer activity.

In this work, the synthesis of silver nanoparticles from a pigment produced by a recently-discovered bacterium, Chryseobacterium artocarpi CECT 8497, was achieved, followed by an investigation of its anticancer properties. The bacterial pigment was identified as flexirubin following NMR ((1)H NMR and (13)C NMR), UV-Vis, and LC-MS analysis. An aqueous silver nitrate solution was treated with isolated flexirubin to produce silver nanoparticles. The synthesised silver nanoparticles were subsequently characterised by UV-Vis spectroscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), X-Ray Diffraction (XRD), and Fourier Transform Infrared (FTIR) Spectroscopy methodologies. Furthermore, the anticancer effects of synthesised silver nanoparticles in a human breast cancer cell line (MCF-7) were evaluated. The tests showed significant cytotoxicity activity of the silver nanoparticles in the cultured cells, with an IC50 value of 36µgmL(-1). This study demonstrates that silver nanoparticles, synthesised from flexirubin from C. artocarpi CECT 8497, may have potential as a novel chemotherapeutic agent.

PVDF-ErGO-GRC electrode: A single setup electrochemical system for separation, pre-concentration and detection of lead ions in complex aqueous samples.

An effective electrode was developed based on electromembrane extraction (EME) and square wave voltammetry (SWV) for simultaneous separation, pre-concentration and determination of lead (II) (Pb(II)) ions in complex aqueous samples. Electrochemically reduced graphene oxide-graphite reinforced carbon (ErGO-GRC) was utilized in conjunction with the SWV. Pb(II) ions were extracted from an aqueous sample solution into an acidic acceptor phase (1M HCl) in the lumen of the polyvinylidene fluoride (PVDF) membrane bag by the application of voltage of maximum 6 V across the supported liquid membrane (SLM), consisting of organic solvent and di-(2-ethylhexyl)phosphoric acid (D2EHPA). The parameters affecting the EME were optimized for Pb(II) ions. The optimum EME conditions were found to be 20% D2EHPA in 1-octanol impregnated in the wall of PVDF membrane (PVDF17) as the SLM, extraction time of 20 min, pH of sample solution of 8 and a voltage of 5 V. The PVDF-ErGO-GRC electrode system attained enrichment factors of 40 times and 80% of extraction with relative standard deviations (n=5) of 8.3%. Good linearity ranging from 0.25 to 2 nM with coefficients correlation of 0.999 was obtained. The Pb(II) ions detection limit of PVDF-ErGO-GRC electrode was found to be 0.09 nM. The newly developed single setup electrochemical system was applied to complex aqueous samples such as tap, river and sea water to evaluate the feasibility of the method for applications.

A sensitive, selective and rapid determination of lead(II) ions in real-life samples using an electrochemically reduced graphene oxide-graphite reinforced carbon electrode.

In this study, a sensitive and cost-effective electrochemically reduced graphene oxide (ErGO) on graphite reinforced carbon (GRC) was developed for the detection of lead (Pb(II)) ions present in the real-life samples. A film of graphene oxide (GO) was drop-casted on GRC and their electrochemical properties were investigated using cyclic voltammetry (CV), amperometry and square wave voltammetry (SWV). Factors influencing the detection of Pb(II) ions, such as grades of GRC, constant applied cathodic potential (CACP), concentration of hydrochloric acid and drop-casting drying time were optimised. GO is irreversibly reduced in the range of -0.7 V to -1.6 V vs Ag/AgCl (3 M) in acidic condition. The results showed that the reduction behaviour of GO contributed to the high sensitivity of Pb(II) ions detection even at nanomolar level. The ErGO-GRC showed the detection limit of 0.5 nM and linear range of 3-15 nM in HCl (1 M). The developed electrode has potential to be a good candidate for the determination of Pb(II) ions in different aqueous system. The proposed method gives a good recovery rate of Pb(II) ions in real-life water samples such as tap water and river water.

Identification of naphthalene metabolism by white rot fungus Pleurotus eryngii.

The use of biomaterials or microorganisms in PAHs degradation had presented an eye-catching performance. Pleurotus eryngii is a white rot fungus, which is easily isolated from the decayed woods in the tropical rain forest, used to determine the capability to utilize naphthalene, a two-ring polycyclic aromatic hydrocarbon as source of carbon and energy. In the meantime, biotransformation of naphthalene to intermediates and other by-products during degradation was investigated in this study. Pleurotus eryngii had been incubated in liquid medium formulated with naphthalene for 14 days. The presence of metabolites of naphthalene suggests that Pleurotus eryngii begin the ring cleavage by dioxygenation on C1 and C4 position to give 1,4-naphthaquinone. 1,4-Naphthaquinone was further degraded to benzoic acid, where the proposed terepthalic acid is absent in the cultured extract. Further degradation of benzoic acid by Pleurotus eryngii shows the existence of catechol as a result of the combination of decarboxylation and hydroxylation process. Unfortunately, phthalic acid was not detected in this study. Several enzymes, including manganese peroxidase, lignin peroxidase, laccase, 1,2-dioxygenase and 2,3-dioxygenase are enzymes responsible for naphthalene degradation. Reduction of naphthalene and the presence of metabolites in liquid medium showed the ability of Pleurotus eryngii to utilize naphthalene as carbon source instead of a limited glucose amount.

Degradation and transformation of anthracene by white-rot fungus Armillaria sp. F022.

Characterization of anthracene metabolites produced by Armillaria sp. F022 was performed in the enzymatic system. The fungal culture was conducted in 100-mL Erlenmeyer flask containing mineral salt broth medium (20 mL) and incubated at 120 rpm for 5-30 days. The culture broth was then centrifuged at 10,000 rpm for 45 min to obtain the extract. Additionally, the effect of glucose consumption, laccase activity, and biomass production in degradation of anthracene were also investigated. Approximately, 92 % of the initial concentration of anthracene was degraded within 30 days of incubation. Dynamic pattern of the biomass production was affected the laccase activity during the experiment. The biomass of the fungus increased with the increasing of laccase activity. The isolation and characterization of four metabolites indicated that the structure of anthracene was transformed by Armillaria sp. F022 in two routes. First, anthracene was oxidized to form anthraquinone, benzoic acid, and second, converted into other products, 2-hydroxy-3-naphthoic acid and coumarin. Gas chromatography-mass spectrometry analysis also revealed that the molecular structure of anthracene was transformed by the action of the enzyme, generating a series of intermediate compounds such as anthraquinone by ring-cleavage reactions. The ligninolytic enzymes expecially free extracellular laccase played an important role in the transformation of anthracene during degradation period.

Identification of naphthalene metabolism by white rot fungus Armillaria sp. F022.

Armillaria sp. F022, a white rot fungus isolated from tropical rain forest (Samarinda, Indonesia) was used to biodegrade naphthalene in cultured medium. Transformation of naphthalene by Armillaria sp. F022 which is able to use naphthalene, a two ring-polycyclic aromatic hydrocarbon (PAH) as a source of carbon and energy was investigated. The metabolic pathway was elucidated by identifying metabolites, biotransformation studies and monitoring enzyme activities in cell-free extracts. The identification of metabolites suggests that Armillaria sp. F022 initiates its attack on naphthalene by dioxygenation at its C-1 and C-4 positions to give 1,4-naphthoquinone. The intermediate 2-hydroxybenzaldehyde and salicylic acid, and the characteristic of the meta-cleavage of the resulting diol were identified in the long-term incubation. A part from typical metabolites of naphthalene degradation known from mesophiles, benzoic acid was identified as the next intermediate for the naphthalene pathway of this Armillaria sp. F022. Neither phthalic acid, catechol and cis,cis-muconic acid metabolites were detected in culture extracts. Several enzymes (manganese peroxidase, lignin peroxidase, laccase, 1,2-dioxygenase and 2,3-dioxygenase) produced by Armillaria sp. F022 were detected during the incubation.