Identification of metabolites produced during the complete biodegradation of 1-butyl-3-methylimidazolium chloride by an enriched activated sludge microbial community

A novel insight on the intensification mechanism of sludge dewaterability by ionic liquids

The huge output of sewage sludge has caused a remarkable environmental burden. Sludge dewatering is considered as an important way to reduce the sludge volume. Five imidazole-based ionic liquids were used to improve the dewaterability of sewage sludge. 1-ethyl-3-methylimidazolium dihydrogen phosphate ([Emim][H₂PO₄]) was screened out as a potential conditioner of sludge due to its excellent dewatering performance and reusability. The solid content of sludge filter cake after treatment with [Emim][H₂PO₄] was about 10% higher than that of sludge treated by cationic polyacrylamides (CPAM). The intensification mechanism of ionic liquids to the improvement of sludge dewatering performance was studied. The presence of acidic ionic liquids [Emim][H₂PO₄] resulted the increase of zeta potential from -14.57 ± 0.81 mV to -5.60 ± 0.30 mV and led to the protonation of biopolymers. Acidic ionic liquids [Emim][H₂PO₄] inactivated the microorganism and led to a porous and unconsolidated structure of the solid sludge particles. All these effects were conducive to destroy the microstructure of sludge and release water. However, [Emim]Cl, [Bmim][OTf] and [Hmim][OTf] showed little effect on the protonation of ionizable functional groups at near-neutral environment. The dissolution of biopolymer decreased the zeta potential and strengthened the electrostatic repulsion. So, they showed weaker intensification effects than CPAM.

Evaluating the hazardous impact of ionic liquids - Challenges and opportunities

Ionic liquids (ILs), being related to the design of new environmentally friendly solvents, are widely considered for applications within the "green chemistry" concept. Due to their unique properties and wide diversity, ILs allow tailoring new separation procedures and producing new materials for advanced applications. However, despite the promising technical performance, environmental concerns highlighted in recent studies focused on the toxicity and biodegradability of ILs and their metabolites have revealed that ILs safety labels are not as benign as previously claimed. This review refers to the fundamentals about the properties and applications of ILs also in the context of their potential environmental effect. Toxicological issues and harmful effects related to the use of ILs are discussed, including the evaluation of their biodegradability and ecological impact on diverse organisms and ecosystems, also with respect to bacteria, fungi, and cell cultures. In addition, this review covers the tools used to assess the toxicity of ILs, including the predictive computational models and the results of studies involving cell membrane models and molecular simulations. Summing up the knowledge available so far, there are still no reliable criteria for unequivocal attribution of toxicity and environmental impact credentials for ILs, which is a challenging research task.

Isolation and identification of a novel bacterium, Pseudomonas sp. ZyL-01, involved in the biodegradation of CL-20

Hexanitrohexaazaisowurtzitane (CL-20) is a compound with a polycyclic cage and an N-nitro group that has been shown to play an unfavorable role in environmental fate, biosafety, and physical health. The aim of this study was to isolate the microbial community and to identify a single microbial strain that can degrade CL-20 with desirable efficiency. Metagenomic sequencing methods were performed to investigate the dynamic changes in the composition of the community diversity. The most varied genus among the microbial community was Pseudomonas, which increased from 1.46% to 44.63% during the period of incubation (MC0-MC4). Furthermore, the new strain was isolated and identified from the activated sludge by bacterial morphological and 16s rRNA sequencing analyses. The CL-20 concentrations decreased by 75.21 μg/mL and 74.02 μg/mL in 48 h by MC4 and Pseudomonas sp. ZyL-01, respectively. Moreover, ZyL-01 could decompose 98% CL-20 of the real effluent in 14 day's incubation with the glucose as carbon source. Finally, a draft genome sequence was obtained to predict possible degrading enzymes involved in the biodegradation of CL-20. Specifically, 330 genes that are involved in energy production and conversion were annotated by Gene Ontology functional enrichment analysis, and some of these candidates may encode enzymes that are responsible for CL-20 degradation. In summary, our studies indicate that microbes might be a valuable biological resource for the treatment of environmental contamination caused by CL-20 and that Pseudomonas sp. ZyL-01 might be a promising candidate for eradicating CL-20 to achieve a more biosafe environment and improve public health.

Cation and anion effect on the biodegradability and toxicity of imidazolium- and choline-based ionic liquids

This work studies the effect of the cation and anion on the biodegradability and inhibition of imidazolium- and choline-based ionic liquids (ILs) using activated sludge. Six commercial ILs, formed by combination of 1-Butyl-3-methylimidazolium (Bmim⁺) and N,N,N-trimethylethanolammonium (Choline⁺) cations and chloride (Cl^-), acetate (Ac^-) and bis(trifluoromethanesulfonyl)imide (NTf₂^-) anions were evaluated, all representative counter-ions with markedly different toxicity and biodegradability. Inherent and fast biodegradability tests were used to evaluate both the microorganism inhibition and the IL biodegradability. In addition, the ecotoxicological response (EC₅₀) of the ILs was studied using activated sludge and Vibrio fischeri (Microtox® test). Bmim⁺ and NTf₂^- can be considered as non-biodegradable, whereas aerobic microorganisms easily degraded Choline⁺ and Ac^-. The biodegradation pattern of each cation/anion is nearly unaffected by counter-ion nature. Moreover, concentrations of CholineNTf₂ higher than 50 mg/L caused a partial inhibition on microbial activity, in good concordance with its low EC₅₀ (54 mg/L) measured by respiration inhibition test, which alerts on the negative environmental impact of NTf₂-containing ILs on the performance of sewage treatment plants.

In vitro toxicological evaluation of ionic liquids and development of effective bioremediation process for their removal

The present study deals with the cyto-genotoxicological impact of ionic liquids, 1-butyl-3-methylimidazolium bromide, trihexyl tetradecylphosphonium dicyanamide, 1-decyl-3-methylimidazolium tetrafluoroborate, benzyldimethyltetradecylammonium chloride, and 1-butyl-4-methylpyridinium chloride, on animal cells and their biodegradation. The long alkyl chain containing ionic liquids were found to be more toxic whereas benzene functional group in benzyldimethyltetradecylammonium chloride enhances its toxicity. Aerobic bacterial granules, a bacterial consortium, were developed that have promising ability to break down these organic pollutants. These aerobic bacterial granules have been applied for the biodegradation of ionic liquids. The biological oxygen demand (5 days) and chemical oxygen demand parameters confirmed that the biodegradation was solely due to aerobic bacterial granules which further decreased the time period needed for regular biodegradation by biological oxygen demand (28 days). The high resolution mass spectrometry analysis further approved that the degradation of ionic liquids was mainly via removal of the methyl group. Elevated N-demethylase enzyme activity supports the ionic liquids degradation which may be occurring through demethylation mechanism. The amplicon sequencing of aerobic bacterial granules gives insight into the involvement of the bacterial community in the biodegradation process.

Biodegradation and toxicity of emerging contaminants: Isolation of an exopolysaccharide-producing Sphingomonas sp. for ionic liquids bioremediation

Ionic liquids (ILs) have been characterized as contaminants of emerging concern (CEC) that often resist biodegradation and impose toxicity upon environmental release. Sphingomonas sp. MKIV has been isolated as an extreme microorganism capable for biodegradation of major classes of ILs. Six imidazolium-, pyridinium- and ammonium-based ILs (pyridinium trifluoromethanesulfonate [Py][CF₃SO₃], 1-(4-pyridyl)pyridinium chloride [1-4PPy][Cl], 1-butyl-3-methylimidazolium bromide [BMIM][Br], 1-butyl-3-methylimidazolium methanesulfonate [BMIM][MeSO₄], tetrabutylammonium iodide [n-Bu₄N][I] and tetrabutylammonium hexafluorophosphate [n-Bu₄N][PF₆]) were used for microbial growth. The strain achieved 91% and 87% removal efficiency for cultures supplemented with 100 mg L^-1 of [BMIM][MeSO₄] and [n-Bu₄N][I] respectively. The metabolic activity of MKIV was inhibited following preliminary stages of cultures conducted using [BMIM][MeSO₄], [BMIM][Br], [Py][CF₃SO₃] and [n-Bu₄N][PF₆], indicating potential accumulation of inhibitory metabolites. Thus, a comprehensive toxicological study of the six ILs on Aliivibrio fischeri, Daphnia magna and Raphidocelis subcapitata was conducted demonstrating that the compounds impose moderate and low toxicity. The end-products from [BMIM][MeSO₄] and [n-Bu₄N][I] biodegradation were assessed using Aliivibrio fischeri, exhibiting increased environmental impact of the latter following biotreatment. MKIV produced 19.29 g L^-1 of biopolymer, comprising mainly glucose and galacturonic acid, from 25 g L^-1 of glucose indicating high industrial significance for bioremediation and exopolysaccharide production.

Alkaline Technosol contaminated by former mining activity and its culturable autochthonous microbiota

Technosols or technogenic substrates contaminated by potentially toxic elements as a result of iron mining causes not only contamination of the surrounding ecosystem but may also lead to changes of the extent, abundance, structure and activity of soil microbial community. Microbial biomass were significantly inhibited mainly by exceeding limits of potentially toxic metals as arsenic (in the range of 343-511 mg/kg), copper (in the range of 7980-9227 mg/kg), manganese (in the range of 2417-2670 mg/kg), alkaline and strong alkaline pH conditions and minimal contents of organic nutrients. All of the 14 bacterial isolates, belonged to 4 bacterial phyla, Actinobacteria, Firmicutes; β- and γ-Proteobacteria. Thirteen genera and 20 species of microscopic filamentous fungi were recovered. The most frequently found species belonged to genera Aspergillus (A. clavatus, A. niger, A. flavus, A. versicolor, Aspergillus sp.) with the dominating A. niger in all samples, and Penicillium (P. canescens, P. chrysogenum, P. spinulosum, Penicillium sp.). Fungal plant pathogens occurred in all surface samples. These included Bjerkandera adustata, Bionectria ochloleuca with anamorph state Clonostachys pseudochloleuca, Lewia infectoria, Phoma macrostoma and Rhizoctonia sp.