Degradation Of Organochlorines Research Articles

Functionality, characterization and DEGs contribution by engineering isolate Pseudomonas P1 to elucidate the regulation mechanisms of p-chlorophenol-4-Chloroaniline bioremediation

Engineered bacteria are one of the greenest and most profitable biodegradation methods for removing noxious chlorophenols and chloramines from the environment. This study aims to acquire an engineering isolate Pseudomonas P1 that can effectively degrade 4-Chloroaniline (4-CA) and p-Chlorophenol (4-CP) simultaneously, and reveal potential differences in core gene expression and metabolic pathways in practical applications. A protein interaction network diagram was drawn using networkX under Python to count various topological properties of genes interaction network based on whole genome sequencing to reveal the interaction between proteins involved in organochlorine degradation. The core genes expression levels during aerobic degradation of the aforementioned compounds by Pseudomonas P1, which the most excellent degradation specifications at 30 °C, neutral pH and 100 mg/L, was analyzed based on transcriptome sequencing. Importantly, two major pathways exist in Pseudomonas P1 based on transcriptome sequencing during aerobic degradation of the aforementioned compounds. 4-chlorocatechol (4-CC) pathway of 4-CP degradation by multicomponent phenol hydroxylase (DmpONMLKP) and catechol 2,3-dioxygenase (DmpB), which expression levels were notably up-regulated 1.1–3.25 folds and DmpB was the most significant increased. GSH-dependent dehalogenation pathway including GSR, acpD, ahpF, yghU and katE genes to degrade 4-CA, which expression levels were significantly up-regulated 1.0–3.5 folds. The core genes expression changes were further verified by RTq-PCR. Collectively, our results provided an engineered bacteria that can efficiently mineralize 4-CA and 4-CP simultaneously, and clarified that it has two metabolic pathways regulate biodegradation of 4-CA and 4-CP, which can be practiced for in-site bioremediation of chlorophenols and chloramines co-contaminated soil.

Application of immobilized mycelium-based pellets for the removal of organochlorine compounds: a review.

Organochlorines have diverse structures and applications and are included in the list of persistent organic pollutants (POPs) due to their toxicity and environmental persistence. The reduced capacity of conventional wastewater treatment plants to remove these compounds encourages the development of cost-effective and efficient remediation approaches. Fungal biotechnology can contribute to the development of these technologies through their enzymatic machinery but faces several drawbacks related to the use of dispersed mycelium. In this sense, investigations concerning the degradation of organochlorines using immobilized fungi demonstrated an increase in contaminant removal efficiency compared with degradation by free cells. Despite this interest, the mechanisms of immobilized fungi have not been comprehensively reviewed. In this paper, recent advances of laboratory and field studies in organochlorine compounds removal by fungi are reviewed, focusing on the role of immobilization techniques. Firstly, the mechanisms of organochlorines bioconversion by fungi and the factors affecting enzyme activity are elucidated and discussed in detail. Then, the main targeted compounds, fungi, technics, and materials used for immobilization are discussed, as well as their advantages and limitations. Furthermore, critical points for future studies of fungi immobilization for organochlorine removal are proposed.

Non‐traditional atrazine degradation induced by zero‐valent‐copper: process optimization by the Doehlert experimental design, intermediates detection and toxicity assessment

AbstractBACKGROUNDOver recent years, several studies exploring new technologies capable of degrading persistent organochlorine compounds have been published. Special attention has been dedicated to atrazine (ATZ), due to its ecotoxicological relevance together with its frequent detection in the environment. Degradation of organochlorines via zero‐valent metals has gained great importance given its practicality and versatility, zero‐valent‐iron (ZVI) being the most applied metal for this purpose. Alternatively, zero‐valent‐copper (ZVCu) was proved to exhibit higher reactivity against chlorinated aromatics, therefore deserving further investigation.RESULTSThe optimum degradation conditions for ATZ removal with ZVCu were explored through a Doehlert experimental design. The same conditions were tested for the traditional ZVI, which confirmed that ZVCu was more reactive. The analysis of the degradation products suggests that both reductive and oxidative pathways coexist in the studied process.CONCLUSIONSZVCu was effective in ATZ degradation, both by reductive and oxidation pathways, within a wide range of pH values, although faster in acidic media. The resulting solution from the experiment that promoted the fastest degradation is less toxic than ATZ against microalgae Chlorella vulgaris, which is a positive output regarding the application of this process as a pre‐treatment step of ATZ‐contaminated water matrices. © 2018 Society of Chemical Industry

Yarrowia lipolytica NCIM 3589, a tropical marine yeast, degrades bromoalkanes by an initial hydrolytic dehalogenation step.

The widespread industrial use of organobromines which are known persistent organic pollutants has led to their accumulation in sediments and water bodies causing harm to animals and humans. While degradation of organochlorines by bacteria is well documented, information regarding degradation pathways of these recalcitrant organobromines is scarce. Hence, their fates and effects on the environment are of concern. The present study shows that a tropical marine yeast, Yarrowia lipolytica NCIM 3589 aerobically degrades bromoalkanes differing in carbon chain length and position of halogen substitution viz., 2-bromopropane (2-BP), 1-bromobutane (1-BB), 1,5 dibromopentane (1,5-DBP) and 1-bromodecane (1-BD) as seen by an increase in cell mass, release of bromide and concomitant decrease in concentration of brominated compound. The amount of bromoalkane degraded was 27.3, 21.9, 18.0 and 38.3% with degradation rates of 0.076, 0.058, 0.046 and 0.117/day for 2-BP, 1-BB, 1,5-DBP and 1-BD, respectively. The initial product formed respectively were alcohols viz., 2-propanol, 1-butanol, 1-bromo, 5-pentanol and 1-decanol as detected by GC-MS. These were further metabolized to fatty acids viz., 2-propionic, 1-butyric and 1-decanoic acid eventually leading to carbon dioxide formation. Neither higher chain nor brominated fatty acids were detected. An inducible extracellular dehalogenase responsible for removal of bromide was detected with activities of 21.07, 18.82, 18.96 and 26.67 U/ml for 2-BP, 1-BB, 1,5-DBP and 1-BD, respectively. We report here for the first time the proposed aerobic pathway of bromoalkane degradation by an eukaryotic microbe Y. lipolytica 3589, involving an initial hydrolytic dehalogenation step.

Biogeochemical cycles of chlorine in the coniferous forest ecosystem: practical implications

Chlorine – one of the most widespread elements on the Earth – is present in the environment as chloride ion or bound to organic substances. The main source of chloride ions is the oceans while organically bound chlorine (OCl) comes from various sources, including anthropogenic ones. Chlorinated organic compounds were long considered to be only industrial products; nevertheless, organochlorines occur plentifully in natural ecosystems. However, recent investigations in temperate and boreal forest ecosystems have shown them to be products of biodegradation of soil organic matter under participation of chlorine. It is important to understand both the inorganic and organic biogeochemical cycling of chlorine in order to understand processes in the forest ecosystem and dangers as a result of human activities, i.e. emission and deposition of anthropogenic chlorinated compounds as well as those from natural processes. The minireview presented below provides a survey of contemporary knowledge of the state of the art and a basis for investigations of formation and degradation of organochlorines and monitoring of chloride and organochlorines in forest ecosystems, which has not been carried out in the Czech Republic yet.

Production of chloride and hypochlorite for analytical purposes by sonochemical degradation of organochlorines

This work was aimed at highlighting the potentialities of the reagent generation by ultrasonic irradiation to produce chloride and hypochlorite solutions for analytical purposes derived from the residues of organochlorines of laboratory effluents. The dependence between the production of chloride obtained from the sonication of effluents containing organochlorines and the irradiation time was evaluated for CCl4, CHCl3, CH2Cl2 and Thiamethoxam®. It was observed that under saturation conditions the production of chloride was highest for CHCl3. Additionally, good precision related to the sonochemical generation of chloride was achieved (RSD < 10%). The extent of sonochemical generation of hypochlorite was also evaluated in the presence of different NaOH concentrations. The hypochlorite generated by the degradation of CCl4 residues was monitored by the reference Berthelot method for NH4+ determination. The results obtained with hypochlorite solution sonochemically generated for different NH4+ concentration were compared with the conventional reagent and no significant difference (95% confidence level) was found.

Effective microbial degradation of organochlorines in fluidised bed reactor

The aerobic microbial treatment of a groundwater contaminated with several organic compounds was investigated. This microbial process was combined with posttreatment by activated carbon. Mixed cultures were immobilised on polyurethane foam carrier material in a fluidised bed reactor. The main contaminants benzene and chlorobenzene were almost completely eliminated. Elimination rates remained high even at hydraulic retention times of about two hours. A complete elimination of the haloorganic compounds resistant to microbial degradation was achieved by subsequent adsorption on activated carbon. On the basis of the elimination rates and hydraulic retention times, established by these investigations, a technical scale plant combining microbial degradation and polishing adsorption can be designed. Due to the high degree of microbial mineralisation the presented process offers economic advantages over conventional methods. The quantity of residual waste products for disposal is also minimised.