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

Joint action of six-component mixtures based on concentration response curves morphological parameter in acute and long-term toxicity assay

Previous studies found that the multi-component mixtures with hormesis concentration-response curves (CRCs) were divided into three types according to the combined toxicity analysis of the segment-based method and σ2(k∙ECx) (the variance of k∙ECx). In this study, the acute and long-term toxicity of six pollutants and 12 six-component mixtures were assessed using microplate toxicity analyses (MTA). The functional relationship between σ2(k·ECx) and effect ratio (ERx) was determined by means of the independent action (IA) and the ER model to systematically investigate the correlation between mixture types in acute and long-term toxicity. The results indicated that across the entire concentration range, the mixture type of acute toxicity was consistent with short time exposure (0.25 h) measured in the long-term toxicity experiment. In the inhibition effect range, the types of mixtures of acute toxicity remained consistent with the chronic toxicity (exposure for 24 h) in 11 of the 12 mixtures. This study clarified the changes in the joint action of multi-component mixtures on Aliivibrio fischeri in terms of acute and long-term toxicity. The chronic toxicity of the mixtures can be predicted from the acute toxicity results, which provides a theoretical basis for the biological toxicity evaluation of multi-component mixtures.

Removal of Ibuprofen in Water by Bioaugmentation with Labrys neptuniae CSW11 Isolated from Sewage Sludge-Assessment of Biodegradation Pathway Based on Metabolite Formation and Genomic Analysis

Ibuprofen (IBP) is one of the most consumed drugs in the world. It is only partially removed in wastewater treatment plants (WWTPs), being present in effluent wastewater and sewage sludge, causing the widespread introduction of IBP as an emergent xenobiotic in different environmental compartments. This study describes the use of Labrys neptuniae CSW11, recently described as an IBP degrader, through bioaugmentation processes for the removal of IBP from water under different conditions (additional carbon sources, various concentrations of glucose and IBP). L. neptuniae CSW11 showed very good results in a wide range of IBP concentrations, with 100% removal in only 4 days for 1 and 5 mg L-1 IBP and 7 days for 10 mg L-1, and up to 48.4% removal in 28 days for IBP 100 mg L-1 when using glucose 3 g L-1 as an additional carbon source. Three IBP metabolites were identified during the biotransformation process: 1-hydroxyibuprofen (1-OH-IBP), 2-hydroxyibuprofen (2-OH-IBP), and carboxyibuprofen (CBX-IBP), whose concentrations declined drastically in the presence of glucose. IBP metabolites maintained a certain degree of toxicity in solution, even when IBP was completely removed. The results indicate that L. neptuniae CSW11 can be quite effective in degrading IBP in water, but the bioaugmentation method should be improved using CSW11 in consortia with other bacterial strains able to degrade the toxic metabolites produced. A genome-based analysis of L. neptuniae CSW11 revealed different enzymes that could be involved in IBP biodegradation, and a potential metabolic pathway was proposed based on the metabolites observed and genome analysis.

Impact of permanent dam opening on the fate of polycyclic aromatic compounds in industrial sludges accumulated on river banks: In situ approach

The impact of permanent dam opening on the fate of organic contaminants was studied in the specific case of the Orne River industrial deposits. In the downstream part of the Orne River, the river banks were mainly constituted of steelmaking wastes accumulated for decades. Coring was performed before and after the permanent dam opening (performed in November 2019). The core layers were analysed for grain size, element content, mineralogy and polyclic aromatic compound (PAC) concentrations and distributions. The fine grain size, the high iron content (20-35 %), the presence of high temperature iron phases, the high zinc and lead contents were the main characteristics of these steelmaking sludges and came along with high polycyclic aromatic hydrocarbon (PAH) concentrations. The relative enrichment in low molecular weight PAHs associated to the abundance of furans signed the contribution of coal tar in specific layers. Element and grain size results revealed the erosion of about 12 cm of material during the first year of opening. Oxidative conditions were clearly demonstrated by the presence of gypsum along the entire length of the cores collected in 2020 and the years after. Comparing PAC features in the cores collected before and after dam opening, PAH concentrations did not show significant variations, but the molecular distribution of PACs presented significant changes, mainly in the first 30 cm. Indeed, the depletion of oxygenated PACs suggested the preferential leaching of these polar molecules. Leaching might have been enhanced by opening circumstances and/or the intense flood occurring few months after dam opening. Several PAC ratios were used to confirm the leaching and oxidative processes.

Occurrence, fate, and potential impacts of wood preservatives in the environment: Challenges and environmentally friendly solutions

Wood preservation has gained global prevalence in recent years, primarily owing to the renewable nature of wood and its capacity to act as a carbon sink. Wood, in its natural form, lacks intrinsic resilience and is prone to decay if left untreated; hence, wood preservatives (WPs) are used to improve wood's longevity. The fate and potential hazards of wood preservatives to human health, ecosystems, and the environment are complex and depend on various aspects, including the type of the preservative compounds, their physicochemical properties, application methods, exposure pathways, environmental conditions, and safety measures and guidelines. The occurrence and distribution of WPs in environmental matrices such as soil and water can result in hazardous pollutants seeping into surface water, groundwater, and soil, posing health hazards, and polluting the environment. Bioremediation is crucial to safeguarding the environment and effectively removing contaminants through hydrolytic and/or photochemical reactions. Phytoremediation, vermicomposting, and sustainable adsorption have demonstrated significant efficacy in the remediation of WPs in the natural environment. Adsorbents derived from biomass waste have been acknowledged for their ability to effectively remove WPs, while also offering cost-efficiency and environmental sustainability. This paper aims to identify wood preservatives' sources and fate in the environment and present a comprehensive overview of the latest advancements in environmentally friendly methods relevant to the removal of the commonly observed contaminants associated with WPs in environmental matrices.

Ibuprofen-enhanced biodegradation in solution and sewage sludge by a mineralizing microbial consortium. Shift in associated bacterial communities

Ibuprofen (IBP) is a widely used drug of environmental concern as emerging contaminant due to its low elimination rates by wastewater treatment plants (WWTPs), leading to the contamination of the environment, where IBP is introduced mainly from wastewater discharge and sewage sludge used as fertilizer. This study describes the application of a consortium from sewage sludge and acclimated with ibuprofen (consortium C7) to accelerate its biodegradation both in solution and sewage sludge. 500 mg L-1 IBP was degraded in solution in 28 h, and 66% mineralized in 3 days. IBP adsorbed in sewage sludge (10 mg kg-1) was removed after bioaugmentation with C7 up to 90% in 16 days, with a 5-fold increase in degradation rate. This is the first time that bioaugmentation with bacterial consortia or isolated bacterial strains have been used for IBP degradation in sewage sludge. The bacterial community of consortium C7 was significantly enriched in Sphingomonas wittichii, Bordetella petrii, Pseudomonas stutzeri and Bosea genosp. after IBP degradation, with a special increase in abundance of S. wittichii, probably the main potential bacterial specie responsible for IBP mineralization. Thirteen bacterial strains were isolated from C7 consortium. All of them degraded IBP in presence of glucose, especially Labrys neptuniae. Eight of these bacterial strains (B. tritici, L. neptuniae, S. zoogloeoides, B. petrii, A. denitrificans, S. acidaminiphila, P. nitroreducens, C. flaccumfaciens) had not been previously described as IBP-degraders. The bacterial community that makes up the indigenous consortium C7 appears to have a highly efficient biotic degradation potential to facilitate bioremediation of ibuprofen in contaminated effluents as well as in sewage sludge generated in WWTPs.

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.

Application of Ozonation-Biodegradation Hybrid System for Polycyclic Aromatic Hydrocarbons Degradation

Creosote, a mixture of polycyclic aromatic hydrocarbons (PAHs), was and is a wood impregnate of widespread use. Over the years the accumulation of creosote PAHs in soils and freshwaters has increased, causing a threat to ecosystems. The combined ozonation-biodegradation process is proposed to improve the slow and inefficient biodegradation of creosote hydrocarbons. The impact of different ozonation methods on the biodegradation of model wastewater was evaluated. The biodegradation rate, the changes in chemical oxygen demand, and the total organic carbon concentration were measured in order to provide insight into the process. Moreover, the bacteria consortium activity was monitored during the biodegradation step of the process. The collected data confirmed the research hypothesis, which was that the hybrid method can improve biodegradation. The pre-ozonation followed by inoculation with a bacteria consortium resulted in a significant increase in the biodegradation rate. It allows for the shortening of the time required for the consortium to reach maximum degradation effectiveness and cell activity. Hence, the study gives an important and useful perspective for the decontamination of creosote-polluted ecosystems.

Mechanisms of biostimulant-enhanced biodegradation of PAHs and BTEX mixed contaminants in soil by native microbial consortium

Despite the co-occurrence of polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene, and xylene (BTEX) in the field, to date, knowledge on the bioremediation of benzene and benzo[a]pyrene (BaP) mixed contaminants is limited. In this study, the mechanisms underlying the biodegradation of benzene and BaP under individual and co-contaminated conditions followed by the enhanced biodegradation using methanol, ethanol, and vegetable oil as biostimulants were investigated. The results demonstrated that the benzene biodegradation was highly reduced under the co-contaminated condition compared to the individual benzene contamination, whereas the BaP biodegradation was slightly enhanced with the co-contamination of benzene. Moreover, biostimulation significantly improved the biodegradation of both contaminants under co-contaminated conditions. A trend of significant reduction in the bioavailable BaP contents was observed in all biostimulant-enhanced groups, implying that the bioavailable BaP was the preferred biodegradable BaP fraction. Furthermore, the enzymatic activity analysis revealed a significant increase in lipase and dehydrogenase (DHA) activities, as well as a reduction in the catalase and polyphenol oxidase, suggesting that the increased hydrolysis of fats and proton transfer, as well as the reduced oxidative stress, contributed to the enhanced benzene and BaP biodegradation in the vegetable oil treatment. In addition, the microbial composition analysis results demonstrated that the enriched functional genera contributed to the increased biodegradation efficiency, and the functional genera in the microbial consortium responded differently to different biostimulants, and competitive growth was observed in the biostimulant-enhanced treatments. In addition, the enrichment of Pseudomonas and Rhodococcus species was noticed during the biostimulation of benzene and BaP co-contamination soil, and was positively correlated with the DHA enzyme activities, indicating that these species encode DHA genes which contributed to the higher biodegradation. In conclusion, multiple lines of evidence were provided to shed light on the mechanisms of biostimulant-enhanced biodegradation of PAHs and BTEX co-contamination with native microbial consortiums.

Assessment of bioremediation potential of petroleum-contaminated soils from the shanbei oilfield of China revealed by qPCR and high throughput sequencing

With the crude oil exploration activities in the Shanbei oilfield of China, the risk of soil contamination with crude oil spills has become a major concern. This study aimed at assessing the bioremediation potential of the petroleum polluted soils by investigating the expression of key functional genes decoding alkane and aromatic component degradation using an array of primers and real-time quantitative PCR (qPCR), and the functional microbiomes were determined using a combination of substrate-induced metabolic responses and high throughput sequencing. The results showed that the species that were more inclined to degrade aliphatic fraction of crude oil included Acinetobacter, Stenotrophomonas, Neorhizobium and Olivebacter. And Pseudomonas genus was a highly specific keystone species with the potential to degrade PAH fraction. Both aliphatic and PAH-degrading genes were upregulated when the soil petroleum contents were less than 10,000 mg/kg but downregulated when the oil contents were over 10,000 mg/kg. Bioremediation potential could be feasible for medium pollution with petroleum contents of less than 10,000 mg/kg. Optimization of the niche of Acinetobacter, Stenotrophomonas, Pseudomonas, Neorhizobium and Olivebacter species was beneficial to the biodegradation of refractory hydrocarbon components in the Shanbei plateau oilfield.

Dissipation of a mix of priority PAHs in soils by using availability enhancers. Effect of aging and pollutant interactions

A remediation strategy using three non-toxic availability enhancers (two cyclodextrins and a rhamnolipid biosurfactant) was applied to various soils artificially contaminated with a mix of Polycyclic Aromatic Hydrocarbons (PAHs) considered priority pollutants at two levels of contamination: only with 7 low molecular weight PAHs (LMW PAHs, 5 with 3-ring and 2 with 4-ring - fluoranthene and pyrene) or with 14 PAHs (from 3 to 6 rings). Natural attenuation of PAHs in all soils showed degradation capacity for the LMW PAHs, with a final content of LMW PAHs <5% of their initial concentration. Conversely, the rest of PAHs (high molecular weight PAHs, HMW) remained in the soils (61% - 83.5%), indicating abiotic dissipation of HMW PAHs due to formation of non-extractable residues in soils. The influence of the presence of HMW PAHs on the degradation of the 7 LMW PAHs was also tested, showing a general decrease in the time to obtain 50% dissipation (DT₅₀), statistically significant for acenaphthene, acenaphthylene and fluorene. Availability enhancers showed different effects on PAHs dissipation. 2-hydroxypropyl-β-cyclodextrin (HP) decreased DT₅₀ of some of the lighter PAHs, whereas the rhamnolipid (RL) caused a slight DT₅₀ increase due to its initial toxicity on native soil microorganisms, but showing later high degradation rate for LMW PAHs. On the contrary, randomly methylated-β-cyclodextrin (RAMEB) slowed down PAHs degradation due to its high adsorption onto soil surface, blocking the desorption of PAHs from the soils. The high number of experimental factors not studied simultaneously before (soil type, co-contamination, availability enhancers and incubation time) allowed to conduct a statistical analysis which supported the conclusions reached. Principal Component Analysis separated the studied PAHs in 3 groups, in relation with their molecular weight and Kow. The first principal component was related with LMW PAHs, and separate the inefficient RAMEB from the other availability enhancers.

Bioremediation of PAHs and heavy metals co-contaminated soils: Challenges and enhancement strategies

Systemic studies on the bioremediation of co-contaminated PAHs and heavy metals are lacking, and this paper provides an in-depth review on the topic. The released sources and transport of co-contaminated PAHs and heavy metals, including their co-occurrence through formation of cation-π interactions and their adsorption in soil are examined. Moreover, it is investigated that co-contamination of PAHs and heavy metals can drive a synergistic positive influence on bioremediation through enhanced secretion of extracellular polymeric substances (EPSs), production of biosynthetic genes, organic acid and enzymatic proliferation. However, PAHs molecular structure, PAHs-heavy metals bioavailability and their interactive cytotoxic effects on microorganisms can exert a challenging influence on the bioremediation under co-contaminated conditions. The fluctuations in bioavailability for microorganisms are associated with soil properties, chemical coordinative interactions, and biological activities under the co-contaminated PAHs-heavy metals conditions. The interactive cytotoxicity caused by the emergence of co-contaminants includes microbial cell disruption, denaturation of DNA and protein structure, and deregulation of antioxidant biological molecules. Finally, this paper presents the emerging strategies to overcome the bioavailability problems and recommends the use of biostimulation and bioaugmentation along with the microbial immobilization for enhanced bioremediation of PAHs-heavy metals co-contaminated sites. Better knowledge of the bioremediation potential is imperative to improve the use of these approaches for the sustainable and cost-effective remediation of PAHs and heavy metals co-contamination in the near future.

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.

Microbial Consortia Are Needed to Degrade Soil Pollutants

Soil pollution is one of the most serious environmental problems globally due to the weak self-purification ability, long degradation time, and high cost of cleaning soil pollution. The pollutants in the soil can be transported into the human body through water or dust, causing adverse effects on human health. The latest research has shown that the clean-up of soil pollutants through microbial consortium is a very promising method. This review provides an in-depth discussion on the efficient removal, bio-adsorption, or carbonated precipitation of organic and inorganic pollutants by the microbial consortium, including PAHs, BPS, BPF, crude oil, pyrene, DBP, DOP, TPHP, PHs, butane, DON, TC, Mn, and Cd. In view of the good degradation ability of the consortium compared to single strains, six different synergistic mechanisms and corresponding microorganisms are summarized. The microbial consortium obtains such activities through enhancing synergistic degradation, reducing the accumulation of intermediate products, generating the crude enzyme, and self-regulating, etc. Furthermore, the degradation efficiency of pollutants can be greatly improved by adding chemical materials such as the surfactants Tween 20, Tween 80, and SDS. This review provides insightful information regarding the application of microbial consortia for soil pollutant removal.

Recent Advances in the Study of the Remediation of Polycyclic Aromatic Compound (PAC)-Contaminated Soils: Transformation Products, Toxicity, and Bioavailability Analyses

Polycyclic aromatic compounds (PACs) encompass a diverse group of compounds, often found in historically contaminated sites. Different experimental techniques have been used to remediate PACs-contaminated soils. This brief review surveyed over 270 studies concerning remediation of PACs-contaminated soils and found that, while these studies often measured the concentration of 16 parent polycyclic aromatic hydrocarbons (PAHs) pre- and post-remediation, only a fraction of the studies included the measurement of PAC-transformation products (PAC-TPs) and other PACs (n = 33). Only a few studies also incorporated genotoxicity/toxicity/mutagenicity analysis pre- and post-remediation (n = 5). Another aspect that these studies often neglected to include was bioavailability, as none of the studies that included measurement of PAH-TPs and PACs included bioavailability investigation. Based on the literature analysis, future remediation studies need to consider chemical analysis of PAH-TPs and PACs, genotoxicity/toxicity/mutagenicity, and bioavailability analyses pre- and post-remediation. These assessments will help address numerous concerns including, among others, the presence, properties, and toxicity of PACs and PAH-TPs, risk assessment of soil post-remediation, and the bioavailability of PAH-TPs. Other supplementary techniques that help assist these analyses and recommendations for future analyses are also discussed.

Extraction of nonylphenol, pyrene and phenanthrene from sewage sludge and composted biosolids by cyclodextrins and rhamnolipids

Sewage sludge generated by Waste Water Treatment Plants (WWTPs) are frequently used as organic amendments in agriculture, but they contain pollutants such as Potentially Toxic Elements (PTEs) and organic contaminants which contaminate the agricultural soils. The study presented here is part of a larger study based on the application of environmentally friendly chemical and biological techniques to decrease the content of organic pollutants in sewage sludge before agricultural application. The aim of this study was to evaluate the performance of biodegradable extractants, such as some cyclodextrins (CDs), β-cyclodextrin (BCD), hydroxypropyl-β-cyclodextrin (HPBCD) and randomly methylated-β-cyclodextrin (RAMEB), and a biosurfactant (rhamnolipid, RL) on the removal and availability of pyrene (PYR), phenanthrene (PHE) and nonylphenol (NP) from several biosolids samples in order to improve their subsequent biodegradation. The influence of pollutants retention time on biosolids was studied, as well as the effect of each extractant on PTEs solubilization. Results obtained were pollutant and extractant-dependent. BCD extracted similar amounts of pollutants compared to water, whereas HPBCD and RAMEB actually increased the availability of the three pollutants in most of the samples and aging times. RL seems to be the best election for Polycyclic Aromatic Hydrocarbons (PAHs) extraction from biosolids, with percentages of extraction multiplied by more than 80 and 40 times for PHE and PYR, respectively, relative to water extraction. The extraction enhancement was the highest for NP, the most hydrophobic pollutant, reaching more than 500-fold higher with HPBCD and RAMEB. PTEs extractability was not affected by the different CDs used, but RL caused an increment in their soluble content what could endanger a subsequent biodegradation of the organic pollutants.

Modification of the Bacterial Cell Wall—Is the Bioavailability Important in Creosote Biodegradation?

Creosote oil, widely used as a wood preservative, is a complex mixture of different polycyclic aromatic compounds. The soil contamination result in the presence of a specific microcosm. The presented study focuses on the most active strains involved in bioremediation of long-term creosote-contaminated soil. In three soil samples from different boreholes, two Sphingomonas maltophilia (S. maltophilia) and one Paenibacillus ulginis (P. ulginis) strain were isolated. The conducted experiments showed the differences and similarities between the bacteria strains capable of degrading creosote from the same contaminated area. Both S. maltophilia strains exhibit higher biodegradation efficiency (over 50% after 28 days) and greater increase in glutathione S-transferase activity than P. ulginis ODW 5.9. However, S. maltophilia ODW 3.7 and P. ulginis ODW 5.9 were different from the third of the tested strains. The growth of the former two on creosote resulted in an increase in cell adhesion to Congo red and in the total membrane permeability. Nevertheless, all three strains have shown a decrease in the permeability of the inner cell membrane. That suggests the complex relationship between the cell surface modifications and bioavailability of the creosote to microorganisms. The conducted research allowed us to broaden the current knowledge about the creosote bioremediation and the properties of microorganisms involved in the process.

Bacteria involved in biodegradation of creosote PAH - A case study of long-term contaminated industrial area

Polycyclic aromatic hydrocarbons (PAH) contained in creosote oil are particularly difficult to remove from the soil environment. Their hydrophobic character and low bioavailability to soil microorganisms affects their rate of biodegradation. This study was performed on samples of soil that were (for over forty years) subjected to contamination with creosote oil, and their metagenome and physicochemical properties were characterized. Moreover, the study was undertaken to evaluate the biodegradation of PAHs by autochthonous consortia as well as by selected bacteria strains isolated from long-term contaminated industrial soil. From among the isolated microorganisms, the most effective in biodegrading the contaminants were the strains Pseudomonas mendocina and Brevundimonas olei. They were able to degrade more than 60% of the total content of PAHs during a 28-day test. The biodegradation of these compounds using AT7 dispersant was enhanced only by Serratia marcescens strain. Moreover, the addition of AT7 improved the effectiveness of fluorene and acenaphthene biodegradation by Serratia marcescens 6-fold. Our results indicated that long-term contact with aromatic compounds induced the bacterial strains to use the PAHs as a source of carbon and energy. We observed that supplementation with surfactants does not increase the efficiency of hydrocarbon biodegradation.

Preparation of Lignin Nanoparticles with Entrapped Essential Oil as a Bio-Based Biocide Delivery System

Lignin isolated from beech sawdust was used for the preparation of lignin nanoparticles (LNPs) with entrapped essential oil (EO) from cinnamon bark (Cinnamomum zeylanicum Blume), common thyme (Thymus vulgaris L.), and wild thyme (Thymus serpyllum L.) using a fast antisolvent method. Analysis of EO-loaded LNPs by pyrolysis-gas chromatography-mass spectrometry and Fourier transform infrared spectroscopy confirmed molecular interaction between EOs and LNPs. Quantification of EO incorporation into the LNPs and their in vitro release profiles were assessed by reversed phase high-performance liquid chromatography. Utilized EOs were, to different extents, successfully entrapped inside LNPs, which were attributed to extensive π-stacking between aromatic compounds in EOs like cinnamaldehyde, thymol, and carvacrol on one side and aromatic lignin units on the other side. In vitro release of common thyme and wild thyme EOs from EO-loaded LNPs was strongly delayed compared to the use of pure oil, giving a promising outlook for the development of new bio-based biocide delivery systems for wood preservation.

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.