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Arsenic contamination in the environment : the issues and solutions
This book provides an overview to researchers, graduate, and undergraduate students, as well as academicians who are interested in arsenic. It covers human health risks and established cases of human ailments and sheds light on prospective control measures, both biological and physico-chemical. Arsenic (As) is a widely distributed element in the environment having no known useful physiological function in plants or animals. Historically, this metalloid has been known to be used widely as a poison. Effects of arsenic have come to light in the past few decades due to its increasing contamination in several parts of world, with the worst situation being in Bangladesh and West Bengal, India. The worrying issue is the ingestion of arsenic through water and food and associated health risks due to its carcinogenic and neurotoxic nature. The impact of the problem is widespread, and it has led to extensive research on finding both the causes and solutions. These attempts have allowed us to understand the various probable causes of arsenic contamination in the environment, and at the same time, have provided a number of possible solutions. It is reported that more than 200 mineral species contain As. Generally, As binds with iron and sulfur to form arsenopyrite. According to one estimate from the World Health Organization (WHO), contextual levels of As in soil ranges from 1 to 40 mg kg-1. Arsenic toxicity is related to its oxidation state which is present in the medium. As is a protoplastic toxin, due to its consequence on sulphydryl group it interferes in cell enzymes, cell respiration and in mitosis. Exposure of As may occur to humans via several industries, such as refining or smelting of metal ores, microelectronics, wood preservation, battery manufacturing, and also to those who work in power plants that burn arsenic-rich coal.
Book
Contributions of biosurfactants to natural or induced bioremediation
The number of studies dedicated to evaluating the influence of biosurfactants on bioremediation efficiency is constantly growing. Although significant progress regarding the explanation of mechanisms behind biosurfactant-induced effects could be observed, there are still many factors which are not sufficiently elucidated. This corresponds to the fact that although positive influence of biosurfactants is often reported, there are also numerous cases where no or negative effect was observed. This review summarizes the recent finding in the field of biosurfactant-amended bioremediation, focusing mainly on a critical approach towards potential limitations and causes of failure while investigating the effects of biosurfactants on the efficiency of biodegradation and phytoextraction processes. It also provides a summary of successive steps, which should be taken into consideration when designing biosurfactant-related treatment processes.
Journal Article
Anaerobic digestion : making biogas - making energy : the Earthscan expert guide
\"Hundreds of million tonnes of agricultural and food waste are produced each year around the world, most of which is just that, waste. Anaerobic digestion, biogas and the heat and electricity that can be produced from it is still a nascent industry in many countries, yet the benefits of AD spread throughout the community: - Gives good financial returns to farmers and eco-entrepreneurs. - Helps community leaders meet various policies and legislative targets. - Offers an environmentally sensitive waste disposal option. - Provides a local heat and power supply, & creates employment opportunities - Reduces greenhouse gas emissions, as well as providing an organic fertilizer. Although the process of AD itself is relatively simple there are several system options available to meet the demands of different feedstocks. This book describes, in simple, easy to read language the five common systems of AD; how they work, the impact of scale, the basic requirements, the costs and financial implications, and how to get involved in this rapidly growing green industry\"--Provided by publisher.
Book
Role of brassinosteroids in alleviation of phenanthrene– cadmium co-contamination-induced photosynthetic inhibition and oxidative stress in tomato
Heavy metal pollution often occurs together with organic contaminants. Brassinosteroids (BRs) induce plant tolerance to several abiotic stresses, including phenanthrene (PHE) and cadmium (Cd) stress. However, the role of BRs in PHE+Cd co-contamination-induced stress amelioration is unknown. Here, the interactive effects of PHE, Cd, and 24-epibrassinolide (EBR; a biologically active BR) were investigated in tomato plants. The application of Cd (100 μM) alone was more phytotoxic than PHE applied alone (100 μM); however, their combined application resulted in slightly improved photosynthetic activity and pigment content compared with Cd alone after a 40 d exposure. Accumulation of reactive oxygen species and membrane lipid peroxidation were induced by PHE and/or Cd; however, the differences in effect were insignificant between Cd and PHE+Cd. The foliar application of EBR (0.1 μM) to PHE- and/or Cd-stressed plants alleviated photosynthetic inhibition and oxidative stress by causing enhancement of the activity of the enzymes and related transcript levels of the antioxidant system, secondary metabolism, and the xenobiotic detoxification system. Additionally, PHE and/or Cd residues were significantly decreased in both the leaves and roots after application of EBR, more specifically in PHE+Cd-stressed plants when treated with EBR, indicating a possible improvement in detoxification of these pollutants. The findings thus suggest a potential interaction of EBR and PHE for Cd stress alleviation. These results advocate a positive role for EBR in reducing pollutant residues for food safety and also strengthening phytoremediation.
Journal Article
Labile soil carbon inputs mediate the soil microbial community composition and plant residue decomposition rates
Root carbon (C) inputs may regulate decomposition rates in soil, and in this study we ask: how do labile C inputs regulate decomposition of plant residues, and soil microbial communities? In a 14 d laboratory incubation, we added C compounds often found in root exudates in seven different concentrations (0, 0.7, 1.4, 3.6, 7.2, 14.4 and 21.7 mg C g⁻¹ soil) to soils amended with and without ¹³C-labeled plant residue. We measured CO₂ respiration and shifts in relative fungal and bacterial rRNA gene copy numbers using quantitative polymerase chain reaction (qPCR). Increased labile C input enhanced total C respiration, but only addition of C at low concentrations (0.7 mg C g⁻¹) stimulated plant residue decomposition (+2%). Intermediate concentrations (1.4, 3.6 mg C g⁻¹) had no impact on plant residue decomposition, while greater concentrations of C (> 7.2 mg C g⁻¹) reduced decomposition (-50%). Concurrently, high exudate concentrations (> 3.6 mg C g⁻¹) increased fungal and bacterial gene copy numbers, whereas low exudate concentrations (< 3.6 mg C g⁻¹) increased metabolic activity rather than gene copy numbers. These results underscore that labile soil C inputs can regulate decomposition of more recalcitrant soil C by controlling the activity and relative abundance of fungi and bacteria.
Journal Article
Utilization of diverse organophosphorus pollutants by marine bacteria
Anthropogenic organophosphorus compounds (AOPCs), such as phosphotriesters, are used extensively as plasticizers, flame retardants, nerve agents, and pesticides. To date, only a handful of soil bacteria bearing a phosphotriesterase (PTE), the key enzyme in the AOPC degradation pathway, have been identified. Therefore, the extent to which bacteria are capable of utilizing AOPCs as a phosphorus source, and how widespread this adaptation may be, remains unclear. Marine environments with phosphorus limitation and increasing levels of pollution by AOPCs may drive the emergence of PTE activity. Here, we report the utilization of diverse AOPCs by four model marine bacteria and 17 bacterial isolates from the Mediterranean Sea and the Red Sea. To unravel the details of AOPC utilization, two PTEs from marine bacteria were isolated and characterized, with one of the enzymes belonging to a protein family that, to our knowledge, has never before been associated with PTE activity. When expressed in Escherichia coli with a phosphodiesterase, a PTE isolated from a marine bacterium enabled growth on a pesticide analog as the sole phosphorus source. Utilization of AOPCs may provide bacteria a source of phosphorus in depleted environments and offers a prospect for the bioremediation of a pervasive class of anthropogenic pollutants.
Journal Article
Populus alba dioctyl phthalate uptake from contaminated water
Phthalates are micro-pollutants of great concern due to their negative effects on ecosystem functioning and human health. Thanks to its capability in uptake and accumulation of organic pollutants,
Populus alba
L. “Villafranca” clone could be a good candidate for reducing the impacts derived by the persistence of such compounds in the environment. We investigated plant response and uptake of dioctyl phthalate (DOP) by poplar, grown in hydroponics condition, for 21 days with 0, 40, and 400 μg L
−1
of d
4
-DOP. Treated plants, after 21 days of 400 μg L
−1
d
4
-DOP, showed an increase in root dry biomass (+ 29%) at the expense of aerial parts (− 8%) compared with control. The root development could be sustained by the increase of Mg uptake by poplar. LC-MS/MS analysis demonstrated the uptake and accumulation in roots of d
4
-DOP starting from day one (3.5 ± 3.29 and 7.1 ± 3.28 in 40 and 400 μg L
−1
d
4
-DOP respectively), despite volatilization of d
4
-DOP was observed from nutritive solution. The chemical interaction between d
4
-DOP and Zn occurred in roots of plants treated with the high d
4
-DOP concentration, without limiting the Zn concentration in leaves. Results confirm the high tolerance of “Villafranca” clone to xenobiotic and suggest the poplar capability in d
4
-DOP uptake and accumulation at root level.
Journal Article
Removal of diclofenac and mefenamic acid by the white rot fungus Phanerochaete sordida YK-624 and identification of their metabolites after fungal transformation
The non-steroidal anti-inflammatory drugs diclofenac (DCF) and mefenamic acid (MFA) were treated with the white rot fungus Phanerochaete sordida YK-624. DCF completely disappeared and MFA decreased by about 90% after 6 days of treatment. It was also confirmed that the fungus almost completely removed the acute lethal toxicity of DCF and MFA towards the freshwater crustacean Thamnocephalus platyurus after 6 days of treatment. Mass spectrometric and ¹H nuclear magnetic resonance analyses demonstrated that two mono-hydroxylated DCFs (4′-hydroxydiclofenac and 5-hydroxydiclofenac) and one di-hydroxylated DCF (4′,5-dihydroxydiclofenac) were formed via fungal transformation. The four metabolites of MFA were identified as 3′-hydroxymethylmefenamic acid (mono-hydroxylated MFA), 3′-hydroxymethyl-5-hydroxymefenamic acid (di-hydroxylated MFA), 3′-hydroxymethyl-6′-hydroxymefenamic acid (di-hydroxylated MFA) and 3′-carboxymefenamic acid. These results suggest that hydroxylation catalyzed by cytochrome P450 (CYP) in P. sordida YK-624 may be involved in the elimination and detoxification of DCF and MFA. This notion was further supported by the fact that smaller decreases in DCF and MFA were observed in cultures of P. sordida YK-624 incubated with 1-aminobenzotriazole, a known inhibitor of CYP.
Journal Article
Environmental biodegradation of haloarchaea-produced poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in activated sludge
Novel poly(3-hydroxybutyrate-
co
-3-hydroxyvalerate) (PHBHV) copolymers produced by haloarchaea are excellent candidate biomaterials. However, there is no report hitherto focusing on the biodegradation of PHBHV synthesized by haloarchaea. In this study, an environmental biodegradation of haloarchaea-produced PHBHV films, with 10~60 mol% 3-hydroxyvalerate (3HV) composition and different microchemical structures, was studied in nutrition-depleted activated sludge. The changes in mass, molar mass, chemical composition, thermal properties, and surface morphology were monitored. The mass and molar mass of each film decreased significantly, while the PHA monomer composition remained unchanged with time. Interestingly, the sample of random copolymer PHBHV-2 (R-PHBHV-2) (3HV, 30 mol%) had the lowest crystallinity and was degraded faster than R-PHBHV-3 containing the highest 3HV content or the higher-order copolymer PHBHV-1 (O-PHBHV-1) possessing the highest surface roughness. The order of biodegradation rate was in the opposite trend to the degree of crystallizability of the films. Meanwhile, thermal degradation temperature of most films decreased after biodegradation. Additionally, the surface erosion of films was confirmed by scanning electron microscopy. The dominant bacteria probably responsible for the degradation process were identified in the activated sludge. It was inferred that the degradation rate of haloarchaea-produced PHBHV films mainly depended on sample crystallinity, which was determined by monomer composition and microchemical structure and in turn strongly influenced surface morphology.
Journal Article
Role of the intestinal microbiome in low-density polyethylene degradation by caterpillar larvae of the greater wax moth, Galleria mellonella
Recently, a few insects, including the caterpillar larva of the greater wax moth Galleria mellonella , have been identified as avid ‘plastivores’. These caterpillars are able to ingest and metabolize polyethylene at unprecedented rates. While it appears that G. mellonella plays an important role in the biodegradation process, the contribution of its intestinal microbiome remains poorly understood and contested. In a series of experiments, we present strong evidence of an intricate relationship between an intact microbiome, low-density polyethylene (LDPE) biodegradation and the production of glycol as a metabolic by-product. First, we biochemically confirmed that G. mellonella larvae consume and metabolize LDPE, as individual caterpillars fed on polyethylene excreted glycol, but those excretions were reduced by antibiotic treatment. Further, while the gut bacterial communities remained relatively stable regardless of diet, we showed that during the early phases of feeding on LDPE (24–72 h), caterpillars exhibited increased microbial abundance relative to those starved or fed on their natural honeycomb diet. Finally, by isolating and growing gut bacteria with polyethylene as their exclusive carbon source for over 1 year, we identified microorganisms in the genus Acinetobacter that appeared to be involved in this biodegradation process. Taken collectively, our study indicates that during short-term exposure, the intestinal microbiome of G. mellonella is intricately associated with polyethylene biodegradation in vivo .
Journal Article