Biodegradation of cyclodextrins in soil

From capillaries to microchips, green electrophoretic features for enantiomeric separations: A decade review (2013-2022)

Enantioseparation by the electromigration-based method is well-established and widely discussed in the literature. Electrophoretic strategies have been used to baseline resolve complex enantiomeric mixtures, typically using a selector substance into the background electrolyte (BGE) from capillaries to microchips. Along with developing new materials/substances for enantioseparations, it is the concern about the green analytical chemistry (GAC) principles for method development and application. This review article brings a last decade's update on the publications involving enantioseparation by electrophoresis for capillary and microchip systems. It also brings a critical discussion on GAC principles and new green metrics in the context of developing an enantioseparation method. Chemical and green features of native and modified cyclodextrins are discussed. Still, given the employment of greener substances, ionic liquids and deep-eutectic solvents are highlighted, and some new selectors are proposed. For all the mentioned selectors, green features about their production, application, and disposal are considered. Sample preparation and BGE composition in GAC perspective, as well as greener derivatization possibilities, were also addressed. Therefore, one of the goals of this review is to aid the electrophoretic researchers to look where they have not.

Preparation of aromatic β-cyclodextrin nano/microcapsules and corresponding aromatic textiles: A review

Fragrance finishing of textiles is receiving substantial interest, with aromatherapy being one of the most popular aspects of personal health care. However, the longevity of aroma on textiles and presence after subsequent launderings are major concerns for aromatic textiles directly loaded with essential oils. These drawbacks can be weakened by incorporating essential oil-complexed β-cyclodextrins (β-CDs) onto various textiles. This article reviews various preparation methods of aromatic β-cyclodextrin nano/microcapsules, as well as a wide variety of methods for the preparation of aromatic textiles based on them before and after forming, proposing future trends in preparation processes. The review also covers the complexation of β-CDs with essential oils, and the application of aromatic textiles based on β-CD nano/microcapsules. Systematic research on the preparation of aromatic textiles facilitates the realization of green and simple industrialized large-scale production, providing needed application potential in the fields of various functional materials.

Genome analysis for the identification of genes involved in phenanthrene biodegradation pathway in Stenotrophomonas indicatrix CPHE1. Phenanthrene mineralization in soils assisted by integrated approaches

Phenanthrene (PHE) is a highly toxic compound, widely present in soils. For this reason, it is essential to remove PHE from the environment. Stenotrophomonas indicatrix CPHE1 was isolated from an industrial soil contaminated by polycyclic aromatic hydrocarbons (PAHs) and was sequenced to identify the PHE degrading genes. Dioxygenase, monooxygenase, and dehydrogenase gene products annotated in S. indicatrix CPHE1 genome were clustered into different trees with reference proteins. Moreover, S. indicatrix CPHE1 whole-genome sequences were compared to genes of PAHs-degrading bacteria retrieved from databases and literature. On these basis, reverse transcriptase-polymerase chain reaction (RT-PCR) analysis pointed out that cysteine dioxygenase (cysDO), biphenyl-2,3-diol 1,2-dioxygenase (bphC), and aldolase hydratase (phdG) were expressed only in the presence of PHE. Therefore, different techniques have been designed to improve the PHE mineralization process in five PHE artificially contaminated soils (50 mg kg^-1), including biostimulation, adding a nutrient solution (NS), bioaugmentation, inoculating S. indicatrix CPHE1 which was selected for its PHE-degrading genes, and the use of 2-hydroxypropyl-β-cyclodextrin (HPBCD) as a bioavailability enhancer. High percentages of PHE mineralization were achieved for the studied soils. Depending on the soil, different treatments resulted to be successful; in the case of a clay loam soil, the best strategy was the inoculation of S. indicatrix CPHE1 and NS (59.9% mineralized after 120 days). In sandy soils (CR and R soils) the highest percentage of mineralization was achieved in presence of HPBCD and NS (87.3% and 61.3%, respectively). However, the combination of CPHE1 strain, HPBCD, and NS showed to be the most efficient strategy for sandy and sandy loam soils (LL and ALC soils showed 35% and 74.6%, respectively). The results indicated a high degree of correlation between gene expression and the rates of mineralization.

Novel nonylphenol-degrading bacterial strains isolated from sewage sludge: Application in bioremediation of sludge

Nonylphenol (NP) is an anthropogenic pollutant frequently found in sewage sludge due to the insufficient degrading effectiveness of conventional WWTPs and has attracted attention as an endocrine disruptor. The aim of this study was to isolate specific NP-degrading bacteria from sewage sludge to be used in the degradation of this contaminant through bioaugmentation processes in aqueous solution and sewage sludge. Up to eight different bacterial strains were isolated, six of them not previously described as NP degraders. Bacillus safensis CN12 presented the best NP degradation in solution, and glucose used as an external carbon source increased its effect, reaching DT₅₀ degradation values (time to decline to half the initial concentration of the pollutant) of only 0.9 days and a complete degradation in <7 days. Four NP metabolites were identified throughout the biodegradation process, showing higher toxicity than the parent contaminant. In sewage sludge suspensions, the endogenous microbiota was capable of partially degrading NP, but a part remained adsorbed as bound residue. Bioaugmentation was used for the first time to remove NP from sewage sludge to obtain more environmentally friendly biosolids. However, B. safensis CN12 was not able to degrade NP due to its high adsorption on sludge, but the use of a cyclodextrin (HPBCD) as availability enhancer allowed us to extract NP and degrade it in solution. The addition of glucose as an external carbon source gave the best results since the metabolism of the sludge microbiota was activated, and HPBCD was able to remove NP from sewage sludge to the solution to be degraded by B. safensis CN12. These results indicate that B. safensis CN12 can be used to degrade NP in water and sewage sludge, but the method must be improved using consortia of B. safensis CN12 with other bacterial strains able to degrade the toxic metabolites produced.

Bioremediation of a trifluralin contaminated soil using bioaugmentation with novel isolated bacterial strains and cyclodextrin

Trifluralin (TFL) is a highly persistent with a strong adsorption capacity on soil particles herbicide. This study was to isolate microbial consortia and bacterial strains from a soil with a historical application of pesticides to evaluate their potential to degrade TFL in soil. Different bioremediation techniques were considered for increasing the effectiveness of TFL degradation in soil. These techniques consisted of: i) biostimulation, using a nutrients solution (NS); ii) bioaugmentation, using a natural microbial consortium (NMC), seven individual bacterial strains isolated from NMC, and an artificial bacterial consortium formed by the seven TFL-degrading bacterial strains (ABC); iii) bioavailability enhancement, using a biodegradable compound, a randomly methylated cyclodextrin, RAMEB. Biostimulation using NS leads up to 34 % of soil TFL biodegraded after 100 d. When the contaminated soil was inoculated with NMC or ABC consortia, TFL loss increased up to 62 % and 74 %, respectively, with DT₅₀ values (required time for the pollutant concentration to decline to half of its initial value) of 5.9 and 11 d. In the case of soil inoculation with the isolated individual bacterial strains, the extent of TFL biodegradation ranged widely from 2.3 % to 55 %. The most efficient bacterial strain was Arthrobacter aurescens CTFL7 which had not been previously described in the literature as a TFL-degrading bacterium. Bioaugmentation with CTFL7 bacterium was also tested in the presence of RAMEB, provoking a drastic increase in herbicide biodegradation up to 88 %, achieving a DT₅₀ of only 19 d. Cyclodextrins had never been tested before for enhancement of TFL biodegradation. An ecotoxicity assay was performed to confirm that the proposed bioremediation techniques were also capable to reduce toxicity. A Microtox® test showed that after application A. aurescens CTF7 and A. aurescens CTF7 + RAMEB, the TFL-contaminated soil, which initially presented acute toxicity, became non-toxic at the end of the biodegradation experiments.

Cyclodextrin-enabled green environmental biotechnologies

Most of the organic compounds contaminating the environment can form inclusion complexes with cyclodextrins resulting in enhanced solubility (a benefit in soil remediation) or just the opposite: reduced mobility by sorption (a benefit in wastewater treatment). Combining biotechnologies with cyclodextrin, a renewable and biodegradable material, green environmental technologies of high efficiency were developed. For instance, the cyclodextrin-enabled soil washing/flushing technologies combined with bioremediation have been demonstrated in full-scale field experiments. The efficiency of tertiary wastewater treatment by sorption of non-biodegradable xenobiotics, such as residual pharmaceutics, was proved. The biofilm formation in fouling processes can be prevented or reduced either by applying cyclodextrin-based coatings or by manipulation of quorum sensing (bacterial communication) via capturing signal molecules.

Enhanced Biodegradation of Phenylurea Herbicides by Ochrobactrum anthrophi CD3 Assessment of Its Feasibility in Diuron-Contaminated Soils

The phenylurea herbicides are persistent in soil and water, making necessary the de-velopment of techniques for their removal from the environment. To identify new options in this regard, bacterial strains were isolated from a soil historically managed with pesticides. Ochrobactrum anthropi CD3 showed the ability to remove completely herbicides such as diuron, linuron, chlorotoluron and fluometuron from aqueous solution, and up to 89% of isoproturon. In the case of diuron and linuron, their main metabolite, 3,4-dichloroaniline (3,4-DCA), which has a higher toxicity than the parent compounds, was formed, but remained in solution without further degradation. O. anthropi CD3 was also tested for bioremediation of two different agricultural soils artificially contaminated with diuron, employing bioremediation techniques: (i) biostimulation, using a nutrient solution (NS), (ii) bioaugmentation, using O. anthropi CD3, and iii) bioavailability enhancement using 2-hydroxypropyl-β-cyclodextrin (HPBCD). When bioaugmentation and HPBCD were jointly applied, 50% of the diuron initially added to the soil was biodegraded in a range from 4.7 to 0.7 d. Also, 3,4-DCA was degraded in soil after the strain was inoculated. At the end of the soil biodegradation assay an ecotoxicity test confirmed that after inoculating O. anthropi CD3 the toxicity was drastically reduced.

A review on remediation technologies using functionalized Cyclodextrin

Modern lifestyle and alleviated anthropogenic activities have increased the pollutant load, ultimately causing stress on the environment. In industrialization, many harmful compounds are released into the environment polluting air, water, and soil, triggering adverse impacts on the ecosystem and human beings. Therefore, the development of advanced remediation technologies turns out as a significant environmental priority. Less polar cyclic oligosaccharide Cyclodextrin (CD) with cavity binding organic compounds attracted attention by helping effectively as environmental application. The formation of inclusion complexes and modified Cyclodextrin by cross-linking or surface modification enhances their capacity to abate pollutant effectively from the environment. Modification results in the formation of several novel materials such as CD-based composites, nanocomposites, crosslinked polymer or hydrogels, potent cross-linkers, CD-based membranes, and CD immobilized supports. Several environmental remediation technologies based on Cyclodextrin and modified Cyclodextrin have been discussed in detail in this review. Various environmental applications of Cyclodextrin and its derivatives have been discussed, along with their formation, properties, and characterization. Effective removal of organic pollutants, inorganic pollutants, micropollutants, volatile compounds etc., has been explained using several remediation technologies. Based on CD innocuity, this is referred to as the green process. The reversible equilibrium corresponded by the inclusion phenomenon sets a significant trend in the field of CD environmental application to develop techniques by incorporating supramolecular chemistry as well as irreversible methods such as biodegradation and advanced oxidation. It helps in the complete removal of pollutants and ultimately recycling the CD.

Recent Advances in Biopolymeric Membranes towards the Removal of Emerging Organic Pollutants from Water

Herein, this paper details a comprehensive review on the biopolymeric membrane applications in micropollutants' removal from wastewater. As such, the implications of utilising non-biodegradable membrane materials are outlined. In comparison, considerations on the concept of utilising nanostructured biodegradable polymeric membranes are also outlined. Such biodegradable polymers under considerations include biopolymers-derived cellulose and carrageenan. The advantages of these biopolymer materials include renewability, biocompatibility, biodegradability, and cost-effectiveness when compared to non-biodegradable polymers. The modifications of the biopolymeric membranes were also deliberated in detail. This included the utilisation of cellulose as matrix support for nanomaterials. Furthermore, attention towards the recent advances on using nanofillers towards the stabilisation and enhancement of biopolymeric membrane performances towards organic contaminants removal. It was noted that most of the biopolymeric membrane applications focused on organic dyes (methyl blue, Congo red, azo dyes), crude oil, hexane, and pharmaceutical chemicals such as tetracycline. However, more studies should be dedicated towards emerging pollutants such as micropollutants. The biopolymeric membrane performances such as rejection capabilities, fouling resistance, and water permeability properties were also outlined.

Pesticide remediation with cyclodextrins: a review

The aim of this review is to highlight and provide an update on the current development of pesticide remediation methods, focusing on the utilization of different cyclodextrin (CD) molecules. Because of less environmental impact and non-toxic nature, CDs are beneficial for pesticide remediation, reducing environmental risk and health hazards. They are advantageous for the removal of pesticides from contaminated areas, as well as for better pesticide formulation and, posing significant effects on the hydrolysis or degradation of pesticides. The review focuses on the current trend and innovations regarding the methods and strategies employed for using CDs in designing pesticide remediation. Nowadays, in addition to the conventional experimental techniques, molecular simulation approaches are significantly contributing to the study of such phenomena and hence are recognized as a widely used tool.

Effect and mechanism of cyclodextrins on nitrate reduction and bio-activity by S.oneidensis.MR-1

Cyclodextrins (CDs) have been widely used due to the excellent solubilization of hydrophobic organics. However, their effect on the biotransformation process of hydrophilic pollutants is unclear. This study first evaluated the effect and mechanism of CDs on nitrate reduction by S.oneidensis.MR-1. The three CDs (α-CD, β-CD and γ-CD) all accelerated nitrate reduction, among which β-CD had the best effect. The nitrate reduction rate was increased by 21.8% with 0.5 mM β-CD. As for the mechanism, β-CD increased the biomass, membrane permeability and EPS of S.oneidensis.MR-1. The nitrate reductase activity was also increased by 1.34-fold with 0.5 mM β-CD. The current exchange density and the electron transfer system activity were increased by 11.4% and 99.5% in the β-CD-supply system, respectively. It confirmed that β-CD enhanced the biological and electrochemical characteristics and then enhanced bio-activity. This study provides a new understanding of CDs in microbial remediation and broadens the practical application.

Utilization of biodegradable chitosan-derived sponges as oil retainers

An innovative approach of chitosan-derived biodegradable sponges with high sorption capacity, excellent recyclability, and inherent oleophilic properties have been developed for the first time to remove the crude oil polluting the environment. Chitosan-nitrogen mustard ionic carbonate-β-cyclodextrin (CH-NMIC-CD), chitosan-nitrogen mustard ionic carbonate (CH-NMIC), and chitosan (CH) sponges with macropores were prepared using tripolylphosphate (TPP) by adopting subsequent lyophilization. Detailed characterization such as FTIR, TGA, XRD, and SEM has been done to confirm the formation, stability, crystalline nature, and morphology of the prepared sponges. The FTIR spectra confirmed the successful incorporation of NMIC in CH-NMIC-CD and CH-NMIC and the presence of β-CD in the (CH-NMIC-CD). It was found from the TGA results that the presence of β-CD makes the sponge CH-NMIC-CD stable. SEM analysis showed the morphology of the sponges found to be highly porous with interconnected macropores. The oil absorption capacity was 12.30 g_oil/g_ns higher for the sponge CH-NMIC-CD followed by CH-NMIC and CH. The sponges showed reusability excellently even after consecutive sorption-desorption separation cycles for five times. Moreover, the sponges were completely biodegraded within 25 days. The finding holds a promising future to use CH-NMIC-CD sponges in pollutant entrapment particularly in the removal of crude oil and allied area.

Bioaugmentation of PAH-Contaminated Soils With Novel Specific Degrader Strains Isolated From a Contaminated Industrial Site. Effect of Hydroxypropyl-β-Cyclodextrin as PAH Bioavailability Enhancer

A PAHs-contaminated industrial soil was analyzed using PCR amplification of the gene 16S ribosomal RNA for the detection and identification of different isolated bacterial strains potentially capable of degrading PAHs. Novel degrader strains were isolated and identified as Achromobacter xylosoxidans 2BC8 and Stenotrophomonas maltophilia JR62, which were able to degrade PYR in solution, achieving a mineralization rate of about 1% day^-1. A. xylosoxidans was also able to mineralize PYR in slurry systems using three selected soils, and the total extent of mineralization (once a plateau was reached) increased 4.5, 21, and 57.5% for soils LT, TM and CR, respectively, regarding the mineralization observed in the absence of the bacterial degrader. Soil TM contaminated with PYR was aged for 80 days and total extent of mineralization was reduced (from 46 to 35% after 180 days), and the acclimation period increased (from 49 to 79 days). Hydroxypropyl-ß-cyclodextrin (HPBCD) was used as a bioavailability enhancer of PYR in this aged soil, provoking a significant decrease in the acclimation period (from 79 to 54 days) due to an increase in PYR bioavailable fraction just from the beginning of the assay. However, a similar global extension of mineralization was obtained. A. xylosoxidans was then added together with HPBCD to this aged TM soil contaminated with PYR, and the total extent of mineralization decreased to 25% after 180 days, possibly due to the competitive effect of endogenous microbiota and the higher concentration of PYR in the soil solution provoked by the addition of HPBCD, which could have a toxic effect on the A. xylosoxidans strain.

Natural and assisted dissipation of polycyclic aromatic hydrocarbons in a long-term co-contaminated soil with creosote and potentially toxic elements

An enhanced bioremediation strategy was applied to an industrial soil co-contaminated with Polycyclic Aromatic Hydrocarbons (PAHs) and Potentially Toxic Elements (PTEs). Hydroxypropyl-β-cyclodextrin (HPBCD) and a natural mixture of two rhamnolipids (RL) were added to increase PAHs bioavailability, and combined with a microbial consortium (MC) to biodegrade soil PAHs. Bioavailability of only six PAHs (3-, 4-ring PAHs) increased when using HPBCD, with a maximum increase about 2.8-fold higher. The highest dose of HPBCD (5%) enhanced PAH degradation, with the best results for 4-ring PAHs with treatments of HPBCD + MC (up to 48% degradation for pyrene and 43% for fluoranthene), whereas dissipation for 5-ring PAHs was very low and for 6-ring was negligible. The use of RL increased the bioavailability of 13 of the 16 PAHs studied, reaching up to 60-fold higher values for phenanthrene or 18-fold higher for acenaphtene. RL addition did not show degradation improvement in any situation, and even inhibited the scarce degradation observed in the control treatment. The high increase in availability of both PAHs and mainly PTEs when using RL as amendment could make them toxic for microorganisms. In fact, Microtox Acute Toxicity test using Aliivibrio fischeri and the absence of colony forming units (CFUs) of indigenous bacteria demonstrated the extremely high levels of toxicity in RL treated soil.

Degradation kinetics of chlorpyrifos and diazinon in volcanic and non-volcanic soils: influence of cyclodextrins

The intensive use of insecticides such as chlorpyrifos (CPF) and diazinon (DZN) in the agricultural activities worldwide has produced contamination of soils and/or transport to non-target areas including their distribution to surface and groundwaters. Cyclodextrins (CDs) have been proposed as an alternative in remediation technologies based on the separation of contaminants from soils because they could allow a higher bioavailability for their degradation with a low environmental impact. In this work, the degradation pattern of CPF and DZN and the formation and dissipation of the major degradation products 3,5,6-trichloro-2-pyridinol (TCP) and 2-isopropyl-6-methyl-4-pyrimidinol (IMPH) was established in four agricultural volcanic and non-volcanic soils belonging to Andisol, Ultisol, and Mollisol orders. Both pesticides were highly adsorbed in these soils, consequently, with a greater probability of contaminating them. In contrast, the adsorption of their two main metabolites was low or null; therefore, they are potential groundwater contaminants. The degradation processes were studied in the natural and amended soils with β-cyclodextrin (β-CD) and methyl-β-cyclodextrin (Mβ-CD) for CPF and DZN, respectively. A slow degradation of CPF and DZN was obtained for volcanic soils with observable residues until the end of the incubation time (150-180 days). In Mollisols, the higher degradation rate of CPF was favored by the neutral to basic pH, and for DZN it was related to the lower adsorption and higher bioavailability. The amendment of soils with CDs produced slower degradation rates which led to a greater concentration of the compounds at the end of the incubation time. This effect was more pronounced for DZN. The exception was the Andisol, with no significant changes for both compounds regarding the unamended soil. No residues of TCP were observed for this soil in both conditions during the whole incubation time; nevertheless, the accumulation of TCP was significant in the Ultisol and Mollisols, but the concentrations were lower for the amended soils. The accumulation of IMPH was important in Mollisol amended soils; however, their residues were observed in the volcanic soils during the whole incubation period in the natural and amended soils. An important enhancement of the microbial activity occurred in the system β-CD/CPF in Mollisols, without a more effective degradation of the insecticide. The opposite effect was observed in the system Mβ-CD/DZN mainly in the oxidative activity in all soils. The higher degradation of DZN and IMPH in natural Mollisols was related to the higher hydrolytic and oxidative activities. The stability of the inclusion complexes formed could play an important role for explaining the results obtained with the amendments.

Enhanced reductive de-chlorination of a solvent contaminated aquifer through addition and apparent fermentation of cyclodextrin

In a field study, aqueous cyclodextrin (CD) was investigated for its ability to extract chlorinated volatile organic compounds (cVOC), such as trichloroethylene (TCE), 1,1,1-trichloroethane (TCA), and dichloroethene (DCE) through in-situ flushing of a sandy aquifer. After cessation of aquifer flushing, a plume of CD was left. Changes in CD, cVOC, and inorganic terminal electron acceptors (TEAs) (DO, nitrate, sulfate, iron) were monitored in four rounds of wellwater sampling (20, 210, 342, and 425days after cessation of active pumping). Post-CD flushing VOC levels rebounded (850% for TCE, 190% for TCA, and 53% for DCE) between the first two sampling rounds, apparently due to rate-limited desorption from aquifer media and dissolution from remaining NAPL. However, substantial reduction in the mass of TCE (6.3 to 0.11mol: 98%) and TCA (2.8 to 0.73mol: 74%) in groundwater was observed between 210 and 425days. DCE should primarily be produced from the degradation of TCE and is expected to subsequently degrade to chloroethene. Since DCE levels decreased only slightly (0.23 to 0.17mol: 26%), its degradation rate should be similar to that produced from the decaying TCE. Cyclodextrin was monitored starting from day 210. The mass of residual CD (as measured by Total Organic Carbon) decreased from 150mol (day 210) to 66 (day 425) (56% decrease). The naturally anaerobic zone within the aquifer where residual CD mass decreased coincided with a loss of other major potential TEAs: nitrate (97% loss), sulfate (31%) and iron (31%). In other studies, TCE and 1,1,1-TCA have been found to be more energetically favorable TEAs than sulfate and iron and their degradation via reductive dechlorination has been found to be enhanced by the fermentation of carbohydrates. Such processes can explain these observations, but more investigation is needed to evaluate whether residual levels of CD can facilitate the anaerobic degradation of chlorinated VOCs.

Advanced technologies for the remediation of pesticide-contaminated soils

The occurrence of pesticides in soil has become a highly significant environmental problem, which has been increased by the vast use of pesticides worldwide and the absence of remediation technologies that have been tested at full-scale. The aim of this review is to give an overview on technologies really studied and/or developed during the last years for remediation of soils contaminated by pesticides. Depending on the nature of the decontamination process, these techniques have been included into three categories: containment-immobilization, separation or destruction. The review includes some considerations about the status of emerging technologies as well as their advantages, limitations, and pesticides treated. In most cases, emerging technologies, such as those based on oxidation-reduction or bioremediation, may be incorporated into existing technologies to improve their performance or overcome limitations. Research and development actions are still needed for emerging technologies to bring them for full-scale implementation.

Nootkatone encapsulation by cyclodextrins: Effect on water solubility and photostability

Nootkatone (NO) is a sesquiterpenoid volatile flavor, used in foods, cosmetics and pharmaceuticals, possessing also insect repellent activity. Its application is limited because of its low aqueous solubility and stability; this could be resolved by encapsulation in cyclodextrins (CDs). This study evaluated the encapsulation of NO by CDs using phase solubility studies, Isothermal Titration Calorimetry, Nuclear Magnetic Resonance spectroscopy and molecular modeling. Solid CD/NO inclusion complex was prepared and characterized for encapsulation efficiency and loading capacity using UV-Visible. Thermal properties were investigated by thermogravimetric-differential thermal analysis and release studies were performed using multiple headspace extraction. Formation constants (K_f) proved the formation of stable inclusion complexes. NO aqueous solubility, photo- and thermal stability were enhanced and the release could be insured from solid complex in aqueous solution. This suggests that CDs are promising carrier to improve NO properties and, consequently, to enlarge its use in foods, cosmetics, pharmaceuticals and agrochemicals preparations.

Natural attenuation of fluorene and pyrene in contaminated soils and assisted with hydroxypropyl-β-cyclodextrin. Effect of co-contamination

The objectives of this study were to investigate the mutual effect of the PAHs fluorene and pyrene on their respective biodegradation and dissipation processes in an agricultural soil, and to determine the effect of hydroxypropyl-β-cyclodextrin (HPBCD), used to increase the bioavailability of PAHs, on such processes. Fluorene dissipation was primarily due to abiotic processes, although a small contribution from biodegradation was also observed. Therefore, fluorene dissipation did not increase with HPBCD and its presence did not significantly alter the dehydrogenase activity. In contrast to fluorene, pyrene dissipation depended primarily on biotic factors, with endogenous soil microorganisms capable of degrading pyrene, with large increases in dehydrogenase activity. HPBCD increased biodegradation rate of pyrene. The co-contamination of soil with both PAHs did not affect fluorene evolution, but significantly inhibited pyrene biodegradation. The different abilities of soil bacterial consortia to catabolize these PAHs are discussed. Additionally, the possibility that the abiotic loss of fluorene through volatilization had a significant effect on the microbial community biodegradation of both fluorene and pyrene is examined.

Assisted attenuation of a soil contaminated by diuron using hydroxypropyl-β-cyclodextrin and organic amendments

Diuron desorption and mineralisation were studied on an amended and artificially contaminated soil. The amendments used comprised two different composted organic residues i.e., sewage sludge (SS) mixed with pruning wastes, and urban solid residues (USR), and two different solutions (with inorganic salts as the micronutrients and hydroxypropyl-β-cyclodextrin (HPBCD)). After applying micronutrients to activate the soil flora, 15.5% mineralisation could be reached after 150 days, indicating that the soil has a potential capacity to mineralise the herbicide through biostimulation-assisted attenuation. Diuron mineralisation was also improved when HPBCD solutions were applied. Indeed, the extent of herbicide mineralisation reached 29.7% with this application. Moreover, both the lag phase and the half-life time (DT50) were reduced to 33 and 1,778 days, respectively, relative to the application of just micronutrients (i.e., 39 and 6297 days, respectively). Organic amendments were also applied (i.e., USR and SS) on the contaminated soil: it was found that the diuron mineralisation rate was improved as the amendment concentration increased. The joint application of all treatments investigated at the best conditions tested was conducted to obtain the best diuron mineralisation results. The micronutrient amendment plus 4% USR or SS amendment plus HPBCD solution (10-fold diuron initially spiked) caused an extent of diuron mineralisation 33.2 or 46.5%, respectively.

Effect of contact time and the use of hydroxypropyl-β-cyclodextrin in the removal of fluorene and fluoranthene from contaminated soils

Sorption-desorption experiments of fluorene (FLU) and fluoranthene (FLT) in soils were carried out and correlated to their removal from aged contaminated soils using aqueous solutions in the absence and in the presence of hydroxypropyl-β-cyclodextrin (HPBCD) as the extraction agent. FLU became more resistant to extraction in aged contaminated soils due to its initial adsorption onto the mineral and amorphous soil organic matter (SOM) domains, sites of lower binding energy from which, due to its small size, it could spread towards the condensed SOM as the contact time increased. Therefore, FLU will not be easily desorbed from aged contaminated soils due to physical entrapment mechanisms, even when using HPBCD as extractant, presenting FLU low risks to the environment. On the contrary, FLT was extracted from aged soils in the presence of HPBCD in solutions to a much greater extent than in its absence. Due to its more hydrophobic character FLT sorption in soils was relatively quicker, remaining more or less fixed on hydrophobic sites of the organic matter (OM) with different energies, and therefore the amount of FLT extracted was almost constant for different ageing times. During extraction experiments, the influence of the OM quality of the soils was also highlighted because an inverse proportionality between OM content of soil and extractability of sorbed FLT was observed. It was concluded that soils with lower OM content that had more diagenetically processed OM could block the extraction of FLT more effectively than soils with higher OM content that are less humified. This indicates the need to use not only adsorption-desorption data in contaminant fate and transport models, but also extraction studies in aged contaminated soils and other complementary analytical approaches when assessing soil contamination-related risks.

Potential of activated carbon to recover randomly-methylated-β-cyclodextrin solution from washing water originating from in situ soil flushing

Despite the overall high efficacy of cyclodextrins to accelerate the treatment of soil aquifer remediation by in-situ soil flushing, the use in practice remains limited because of the high costs of cyclodextrin and high concentrations needed to significantly reduce the treatment time. The current study tested the potential of activated carbon to treat washing water originating from soil flushing in order to selectively separate hydrocarbon contaminants from washing water containing cyclodextrin and subsequently reuse the cyclodextrin solution for reinfiltration. A high recovery of the cyclodextrin from the washing water would reduce the costs and would make the technique economically feasible for soil remediation. This study aimed to investigate whether cyclodextrin can pass through the activated carbon filter without reducing the cyclodextrin concentration when the contaminated washing water is treated and whether the presence of cyclodextrin negatively affects the purification potential of activated carbon to remove the organic pollutants from the pumped soil water. Lab-scale column experiments showed that with the appropriate activated carbon 100% of cyclodextrin (randomly-methylated-β-cyclodextrin) can be recovered from the washing water and that the effect on the efficiency of activated carbon to remove the hydrocarbon contaminants remains limited. These results show that additional field tests are useful to make in-situ soil flushing with cyclodextrin both a technical and an economical interesting technique. These results might stimulate the application of cyclodextrin in soil treatment technology.

Decontamination of polycyclic aromatic hydrocarbons and nonylphenol from sewage sludge using hydroxypropyl-β-cyclodextrin and evaluation of the toxicity of leachates

A decontamination technique based in cyclodextrin extraction has been developed to eliminate nonylphenol (NP) and 16 polycyclic aromatic hydrocarbons (PAHs; the US Environmental Protection Agency priority pollutants list) from sewage sludge. In a first step, PAHs and NP were characterised in six sludges to determine contamination levels according to limit values proposed by the European Union Sludge Directive draft. There were few variations in the total PAHs content with levels of 1.88 to 3.05 mg kg(-1). Three-ring PAHs predominated, but fluoranthene and pyrene were also present. None of the sludge exceeded the PAHs limit proposed by the European Union's draft Directive. On the contrary, NP content in four of the six sludges was over the recommended limits of 50 mg kg(-1) for NP ethoxylates. With the aim of obtaining NP values below the concentration limits proposed to use the sewage sludge as agricultural amendments, a preliminary study using hydroxypropyl-β-cyclodextrin (HPBCD) extractions as a decontamination technique was carried out. About 90% of NP content was removed with only one extraction with HPBCD, whereas after three sequential extractions using an aqueous solution without HPBCD, the NP extraction percentage was less than 1%. Simultaneously, PAHs extraction percentages obtained with HPBCD were also much higher than when aqueous solution was used, especially in the case of two- and three-ring PAHs. Finally, the potential environmental hazard of HPBCD leachates to aquatic organisms (Daphnia magna) was tested. These results indicate that the treatment of sewage sludge with cyclodextrin could allow their safe use as fertiliser in agriculture.

Mathematical model for cyclodextrin alteration of bioavailability of organic pollutants

While many cyclodextrin-based applications have been developed to assess or enhance bioavailability of organic pollutants, the choice of cyclodextrin (CD) is largely empirical, with little consideration of pollutant diversity and environmental matrix effects. This study aimed at developing a mathematical model for quantifying CD alteration of bioavailability of organic pollutants. Cyclodextrin appears to have multiple effects, together contributing to its bioavailability-enhancing property. Cyclodextrin is adsorbed onto the adsorbent matrix to different extents. The adsorbed CD is capable of sequestrating organic pollutants, highlighting the role of a pseudophase similar to solid environmental matrix. Aqueous CD can reduce adsorption of organic pollutants via inclusion complexation. The two effects cancel each other to a certain degree, which determines the levels of organic pollutants dissolved (comprising freely dissolved and CD-included forms). Additionally, the CD-included form is nearly identical in biological activity to the free form. A mathematical model of one variable (i.e., CD concentration) was derived to quantify effects of CD on the bioavailability of organic pollutants. Model analysis indicates that alteration of bioavailability of organic pollutants by CD depends on both CD (type and level) and environmental matrix. The selection of CD type and amendment level for a given application may be predicted by the model.

Electrokinetic remediation and microbial community shift of β-cyclodextrin-dissolved petroleum hydrocarbon-contaminated soil

Electrokinetic (EK) migration of β-cyclodextrin (β-CD), which is inclusive of total petroleum hydrocarbon (TPH), is an economically beneficial and environmentally friendly remediation process for oil-contaminated soils. Remediation studies of oil-contaminated soils generally prepared samples using particular TPHs. This study investigates the removal of TPHs from, and electromigration of microbial cells in field samples via EK remediation. Both TPH content and soil respiration declined after the EK remediation process. The strains in the original soil sample included Bacillus sp., Sporosarcina sp., Beta proteobacterium, Streptomyces sp., Pontibacter sp., Azorhizobium sp., Taxeobacter sp., and Williamsia sp. Electromigration of microbial cells reduced the biodiversity of the microbial community in soil following EK remediation. At 200 V m(-1) for 10 days, 36% TPH was removed, with a small population of microbial cells flushed out, demonstrating that EK remediation is effective for the present oil-contaminated soils collected in field.

Benzo[a]pyrene degradation using simultaneously combined chemical oxidation, biotreatment with Fusarium solani and cyclodextrins

The interest of simultaneously combining chemical (Fenton's reaction) and biological treatments for the degradation of a high molecular weight polycyclic aromatic hydrocarbon benzo[a]pyrene (BaP) has been studied in laboratory tests. An optimal concentration of 1.5x10(-3) M H(2)O(2) as Fenton's reagent was firstly determined as being compatible with the growth of Fusarium solani, the Deuteromycete fungus used in the biodegradation process. For the enhancement of BaP solubilisation, cyclodextrins were also used in the performed tests. The best degradation performance was achieved through the use of 5x10(-3) M hydroxypropyl-beta-cyclodextrin (HPBCD) in comparison with randomly methylated-beta-cyclodextrin (RAMEB). When Fenton's treatment was combined with biodegradation, a beneficial effect on BaP degradation (25%) was obtained in comparison with biodegradation alone (8%) or with chemical oxidation alone (16%) in the presence of HPBCD for 12 days of incubation.

Development of an innovative soil remediation: "Cyclodextrin-enhanced combined technology"

This paper introduces an in situ "Cyclodextrin-enhanced soil bioremediation technology" which is a combination of 1. in situ bioventilation for biodegradation in the unsaturated soil zone; 2. physico-chemical treatment of the pumped ground water; 3. impulsive flushing for the three-phase soil. For enhancement of biodegradation and solubilization randomly methylated beta-cyclodextrin (RAMEB) was used. An additional aim of this study was to prove the importance of the technology monitoring which was used for characterisation of the soil processes by an integrated methodology. It consists of physico-chemical, biological and ecotoxicological methods specific for the contaminants. For technology monitoring the mobile soil phases--soil gas and ground water--were analysed. Sampling of the whole soil was carried out at the start and end of the technology application. RAMEB resulted in the enhanced removal of pollutants both from the saturated and unsaturated soil zones. Moreover, the biodegradation was more effective than the pump and treat technology, proved by the establishment of the carbon material balance in all soil phases.

Cyclodextrins: a new efficient absorbent to treat waste gas streams

Volatile Organic Compounds (VOCs) in the air provoke health and environmental concerns. This paper focuses on the absorption method to treat industrial polluted air loaded with VOCs. The key variable of this treatment being the choice of a suitable liquid absorbent, the aim of this research work is to investigate the effectiveness and the regeneration of a new potential family of absorbent: cyclodextrins (CDs). All CDs derivatives tested are able to decrease the Henry's law constant of toluene: a reduction of volatility up to 95% may be obtained, depending on CD nature and concentration. Moreover, absorption experiments show that beta-CD, which presents the highest absorption ability, is 250 time more efficient than water. The absorption efficiency is not totally correlated with static experiments, suggesting that, in addition to Henry's law constants and inclusion compounds stability, toluene diffusion into such solutions has to be taken into account. It is also to be noted that salt and pH variations seem to have little influence on the absorption capacity of CDs, which may be of great interest for industrial applications. Finally, since production of solid compounds was not observed during these experiments and since temperature decreases the capture ability in a drastic way, regeneration of the washing solution can be achieved by heating the solution in combination with air stripping.

Conjugates of poly(DL-lactic acid) with ethylenediamino or diethylenetriamino bridged bis(beta-cyclodextrin)s and their nanoparticles as protein delivery systems

Some biodegradable amphiphilic copolymers were synthesized by conjugating poly(DL-lactic acid) (PLA) onto ethylenediamino or diethylenetriamino bridged bis(beta-cyclodextrin)s (bis-CDs). Double emulsion (DE) and nanoprecipitation (NP) methods were used to fabricate the nanoparticles of these copolymers entrapping bovine serum albumin (BSA) as a model protein. Effects of the experimental parameters, such as copolymer composition, BSA concentration, copolymer concentration and poly(vinyl alcohol) concentration, on particular size and encapsulation efficiency (EE) were investigated. Their EE to BSA could reach 83.5% at an optimized condition owing to the cooperative binding effect of the CD moiety with BSA. The core-corona structure of copolymer micelles fabricated from the nanoprecipitation was studied on the basis of 1H NMR and other measurements at various temperatures. The results showed that the core-corona structure kept stable below 50 degrees C (lower than Tg). And increase of the micelle association number occurred above the Tg because the size of the NPs became larger and proton signals of the liquid-like PLA cores could be observed in 1H NMR in D2O at 60 degrees C. The release profiles of NPs showed a burst effect followed by a continuous release. Sodium dodecyl sulfate polyacrylamide gel electrophoresis, circular dichroic and fluorescence spectra were further used to identify the stability of BSA released from the NPs. The nanoparticles from the conjugates have a promising potential in nasal delivery system.