Toluene degradation via a unique metabolic route in indigenous bacterial species

Simultaneous biofiltration of H2S, NH3, and toluene using compost made of chicken manure and sugarcane bagasse as packing material

Offensive odors from wastewater treatment plants (WWTP) are caused by volatile inorganic compounds such as hydrogen sulfide and ammonia and volatile organic compounds (VOCs), such as toluene. To treat these pollutants, biofiltration is an effective and economical technology used worldwide due to its low investment and environmental impact. In this work, a laboratory-scale prototype biofilter unit for the simultaneous biofiltration of hydrogen sulfide, ammonia, and toluene was evaluated by simulating the emission concentrations of the El Salitre WWTP Bogotá, Colombia, using a compost of chicken manure and sugarcane bagasse as packing material for the biofilter. The prototype biofilter unit was set to an operation flow rate of 0.089 m3/h, an empty bed residence time (EBRT) of 60 s, and a volume of 0.007 m3 (6.6 L). The maximum removal efficiency were 96.9 ± 1.2% for H2S, at a loading rate of 4.7 g/m3 h and a concentration of 79.1 mg/m3, 68 ± 2% for NH3, at a loading rate of 1.2 g/m3 h and a concentration of 2.0 mg/m3, and 71.5 ± 4.0% for toluene, at a loading rate of 1.32 g/m3 h and a concentration of 2.3 mg/m3. The removal efficiency of the three compounds decreased when the toluene concentration was increased above 40 mg/m3. However, a recovery of the system was observed after reducing the toluene concentration and after 7 days of inactivity, indicating an inhibitory effect of toluene. These results demonstrate the potential use of the prototype biofilter unit for odor treatment in a WWTP.

Molecular and metabolic characterization of petroleum hydrocarbons degrading Bacillus cereus

Hydrocarbon constituents of petroleum are persistent, bioaccumulated, and bio-magnified in living tissues, transported to longer distances, and exert hazardous effects on human health and the ecosystem. Bioaugmentation with microorganisms like bacteria is an emerging approach that can mitigate the toxins from environmental sources. The present study was initiated to target the petroleum-contaminated soil of gasoline stations situated in Lahore. Petroleum degrading bacteria were isolated by serial dilution method followed by growth analysis, biochemical and molecular characterization, removal efficiency estimation, metabolites extraction, and GC-MS of the metabolites. Molecular analysis identified the bacterium as Bacillus cereus, which exhibited maximum growth at 72 hours and removed 75% petroleum. Biochemical characterization via the Remel RapID™ ONE panel system showed positive results for arginine dehydrolase (ADH), ornithine decarboxylase (ODC), lysine decarboxylase (LDC), o-nitrophenyl-β-D-galactosidase (ONPG), p-nitrophenyl-β-D-glucosidase (βGLU), p-nitrophenyl-N-acetyl-β-D-glucosaminidase (NAG), malonate (MAL), adonitol fermentation (ADON), and tryptophane utilization (IND). GC-MS-based metabolic profiling identified alcohols (methyl alcohol, o-, p- and m-cresols, catechol, and 3-methyl catechol), aldehydes (methanone, acetaldehyde, and m-tolualdehyde), carboxylic acid (methanoic acid, cis,cis-muconic acid, cyclohexane carboxylic acid and benzoic acid), conjugate bases of carboxylic acids (benzoate, cis,cis-muconate, 4-hydroxybenzoate, and pyruvate) and cycloalkane (cyclohexene). It suggested the presence of methane, methylcyclohexane, toluene, xylene, and benzene degradation pathways in B. cereus.

Zinc and copper supplements enhance trichloroethylene removal by Pseudomonas plecoglossicida in water

The effects of two microelements, zinc and copper, on the aerobic co-metabolic removal of trichloroethylene (10 mg/L) by the isolate Pseudomonas plecoglossicida were investigated. The strain was previously isolated from a petroleum-contaminated site using toluene (150 mg/L) as substrate. Different concentrations (1, 10 and 100 mg/L) of microelements provided with SO42- and Cl- were tested. The results showed the supplement of Zn2+ and Cu2+ at the low concentration (1 mg/L) significantly enhanced cell growth. The removal efficiencies for toluene and trichloroethylene were also enhanced at the low concentration (1 mg/L) of Zn2+ and Cu2+. Compared to the control without zinc supplement, higher concentrations of zinc (10 and 100 mg/L) enhanced the removal efficiencies for both toluene and trichloroethylene in the first three days but showed some inhibitory effect afterward. However, the higher concentrations of Cu2+ (10 and 100 mg/L) always showed inhibitory to the toluene removal while showing inhibitory to the TCE removal after three days. For both Zn2+ and Cu2+, the anions SO42- and Cl- did not show significant difference in their effects on the toluene removal. A possible mechanism for Zn2+ and Cu2+ to enhance the removal of toluene and trichloroethylene would be their involvement in toluene oxygenase-based transformation processes. In addition, high concentrations of Zn2+ and Cu2+ ions could be removed from the liquid by the cells accordingly. The results imply a potential of supplementing low concentrations of zinc and copper to enhance bioremediation of the sites co-contaminated with toluene and trichloroethylene.

Metabolic capacity to alter polycyclic aromatic hydrocarbons and its microbe-mediated remediation

The elimination of contaminants caused by anthropogenic activities and rapid industrialization can be accomplished using the widely used technology of bioremediation. Recent years have seen significant advancement in our understanding of the bioremediation of coupled polycyclic aromatic hydrocarbon contamination caused by microbial communities including bacteria, algae, fungi, yeast, etc. One of the newest techniques is microbial-based bioremediation because of its greater productivity, high efficiency, and non-toxic approach. Microbes are appealing candidates for bioremediation because they have amazing metabolic capacity to alter most types of organic material and can endure harsh environmental conditions. Microbes have been characterized as extremophiles that can survive in a variety of environmental circumstances, making them the treasure troves for environmental cleanup and the recovery of contaminated soil. In this study, the mechanisms underlying the bioremediation process as well as the current situation of microbial bioremediation of polycyclic aromatic hydrocarbon are briefly described.

In Vitro, In Silico, and In Vivo Studies of Cardamine hirsuta Linn as a Potential Antidiabetic Agent in a Rat Model

Diabetes mellitus (T2DM) is a multifaceted metabolic disorder with no definite treatment. In silico characterization can help to explain the interaction between molecules and predict 3D structures. The aim of the present study was to evaluate the hypoglycemic activities of the hydro-methanolic extract of Cardamine hirsuta in a rat model. In vitro antioxidant and α-amylase inhibitory assays were evaluated in the present study. Phyto-constituents were quantified using RP-UHPLC-MS analysis. Molecular docking of compounds into the binding site of different molecular targets, i.e., tumor necrosis factor (TNF-α), glycogen synthase kinase 3 β (GSK-3β), and AKT, was carried out. Acute toxicity model, in vivo antidiabetic effect, and the influence on biochemical and oxidative stress parameters were also investigated. T2DM was induced in adult male rats by streptozotocin using a high-fat diet model. Three different doses (125, 250, and 500 mg/kg BW) were orally gavaged for 30 days. Mulberrofuran-M and quercetin3-(6″caffeoylsophoroside) have demonstrated remarkable binding affinity toward TNF-α and GSK-3β, respectively. 2,2-Diphenyl-1-picrylhydrazyl and α-amylase inhibition assay exhibited IC50 values of 75.96 and 73.66 μg/mL, respectively. In vivo findings exhibited that 500 mg/kg body weight (BW) dose of the extract significantly decreased the blood glucose level, improved biochemical parameters as well as oxidative stress by reduction of lipid peroxidation, and increased high-density lipoproteins. Moreover, activities of glutathione-s-transferase, reduced glutathione, superoxide dismutase were enhanced, and cellular architecture in the histopathological examination was restored in treatment groups. The present study affirmed the antidiabetic activities of mulberrofuran-M and quercetin3-(6″caffeoylsophoroside) present in the hydro-methanolic extract of C. hirsuta, possibly due to the reduction in oxidative stress and α-amylase inhibition.

Advanced treatment of toluene emissions with a cutting-edge algal bacterial photo-bioreactor: Performance assessment in a circular economy perspective

A novel approach for the treatment of VOCs (by using toluene used as a model compound) and the simultaneous conversion of carbon dioxide into valuable biomass has been investigated by using a combination of an activated sludge moving bed bioreactor (MBBR) and an algal photo-bioreactor (PBR). The first unit (MBBR, R1) promoted toluene removal up to 99.9 % for inlet load (IL) of 119.91 g m^-3 d^-1. The CO₂ resulting from the degradation of toluene was then fixed in PBR (R2), with a fixation rate up to 95.8 %. The CO₂ uptake was promoted by algae, with average production of algal biomass in Stage VI of 1.3 g L^-1 d^-1. In the contest of the circular economy, alternative sources of nutrients have been assessed, using synthetic urban wastewater (UWW) and dairy wastewater (DWW) for liquid renewal. The produced biomass with DWW showed a high lipid content, with a maximum productivity of 450.25 mg of lipids L^-1 d^-1. The solution proposed may be thus regarded as a sustainable and profitable strategy for VOCs treatment in a circular economy perspective.

Anaerobic mineralization of toluene by enriched soil-free consortia with solid-phase humin as a terminal electron acceptor

The anaerobic biodegradation of toluene proceeds very slowly owing to limited electron acceptors in contaminated aquifer. The liquid reagents traditionally used to enhance this process readily migrate away from the contaminated site, and continuous addition would cause secondary pollution. In our previous study, the reduced solid-phase humic substances (humin), which are redox active, were found to act as electron donors to promote the microbial reactions. Here, we provide new evidence that humin can promote the anaerobic biodegradation of toluene as a terminal electron acceptor. When inoculating nitrate-reducing (NR) and iron-reducing (IR) consortia with toluene degradation activities, the average toluene degradation rates reached 21.20 ± 1.18 μmol/(L·d) and 15.43 ± 0.41 μmol/(L·d) in the presence of a sediment humin (HMcj), and 94.69% ± 4.26% and 93.20% ± 3.73% of the electrons released from toluene oxidation to CO₂ could be recovered by the reduction of HMcj, respectively. Spectroscopy analyses revealed that quinone moieties and nitrogen-containing moieties may be the electron-accepting groups of HMcj. Based on 16S rRNA sequencing, Cellulomonas spp. were the possible functional bacteria in the culture with NR consortium as the inoculum, while Azospira spp., Cellulomonas spp. and Bacillus spp. were the possible functional bacteria in the culture with IR consortium as the inoculum. Further Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) analyses indicated that toluene oxidation and extracellular electron transfer functions were more abundant in HMcj amended cultures, suggesting a possible enhancement mechanism by HMcj. Additionally, experiments using natural groundwater illustrated that toluene degradation was highly dependent on its concentration, HMcj dosage, pH, and salinity. The study of a column filled with HMcj-coated quartz sand demonstrated a desirable level of toluene degradation in a continuous-flow mode without the presence of other electron acceptors. This study provided an effective and green approach for the remediation of the toluene-contaminated groundwater.

Multifold Enhanced Raman Detection of Organic Molecules as Environmental Water Pollutants

Organic molecules, including the benzene series, have been identified as pollutants in environmental water. Due to their very low solubility, they have very small concentrations in water, and they are difficult to be detected by conventional techniques. In particular, there is a lack of real-time, accurate, and rapid detection methods for such molecules in water. However, they are detrimental to human health in many aspects. Toluene has been an important indicator of such environmental pollution detections. In this work, we propose a 3D SERS scheme consisting of a hollow fiber that is coated on the inner wall with densely arranged silver nanoparticles, which supplies multifold Raman enhancement by the plasmonic microcavity. Strong confinement of excitation laser energy and strongly enhanced Raman signals with the bidirectional collection are utilized to achieve high-sensitivity detection of toluene molecules in water. Raman signal with a reasonable signal-to-noise ratio has been measured for a concentration of 0.53 mg/L, indicating a detection limit even lower than this value for such a Raman spectroscopic technique. The corresponding enhancement factor is higher than 6 × 10³ with respect to the available systems. Thus, this device not only enables direct trace detection and real-time monitoring of the water-polluting status by organic molecules but also supplies a practical approach for biological sensing.

Nitrogen-Doped Porous Carbon from Biomass with Efficient Toluene Adsorption and Superior Catalytic Performance

The chemical composition and surface groups of the carbon support affect the adsorption capacity of toluene. To investigate the effect of catalyst substrate on the catalytic performance, two different plant biomasses, banana peel and sugarcane peel, were used as carbon precursors to prepare porous carbon catalyst supports (Cba, Csu, respectively) by a chemical activation method. After decorating PtCo₃ nanoparticles onto both carbon supports (Cba, Csu), the PtCo₃-su catalyst demonstrated better catalytic performance for toluene oxidation (T₁₀₀ = 237 °C) at a high space velocity of 12,000 h^-1. The Csu support possessed a stronger adsorption capacity of toluene (542 mg g^-1), resulting from the synergistic effect of micropore volume and nitrogen-containing functional groups, which led to the PtCo₃-su catalyst exhibiting a better catalytic performance. Moreover, the PtCo₃-su catalyst also showed excellent stability, good water resistance properties, and high recyclability, which can be used as a promising candidate for practical toluene catalytic combustion.

Bioremediation of Soil from Petroleum Contamination

Petroleum is the most common global fossil fuel. It is a complex multi-component system mainly composed of various hydrocarbons such as alkanes, cycloalkanes, mono-, bi- and polyaromatic compounds, resins and asphaltenes. In spite of humanity’s need for petroleum, it negatively affects the environment due to its toxicity. The ecological problem is especially serious at petroleum mining sites or during petroleum transportation. Since it is not possible to replace petroleum with less toxic fuel, ways to reduce the toxic impact of petroleum hydrocarbons on the environment need to be developed. This review addresses bioremediation, a biological approach to petroleum degradation, which is mainly performed by microbes. The pathways of degradation of alkanes, alkenes and aromatic hydrocarbons are presented in detail. The effects of temperature, aeration and the presence of biogenic elements on microbial degradation of petroleum are discussed. Plant–microbe interactions involved with the bioremediation of petroleum-polluted soils are specifically addressed. The data presented in this review point to the great potential of bioremediation practices for cleaning soils of petroleum.

Long-term degradation of toluene and phenol in soil: Identification of transformation products and pathways via HRMS-based suspect and non-target screening

In this study, the long-term fate of toluene and phenol in the soil was investigated, and the transformation products (TPs) and pathways of these compounds were studied by a high resolution mass spectrometry (HRMS)-based suspect and non-target screening approach for the first time, and 9 and 12 transformation products were identified for toluene and phenol, respectively in the lab-exposed soil samples. Salicylaldehyde, 4-hydroxybenzaldehyde, and benzaldehyde were identified in toluene-contaminated field soil samples for the first time, and the main mechanisms involved in the biodegradation and detoxification of toluene and phenol in soil were oxidation, carboxylation, dehydroxylation, and ring fission amongst others. 2-oxoglutarate, TP165-A, TP165-B, TP172, and TP195 were identified as novel phenol transformation products, while salicylaldehyde, 2-oxoglutarate, TP165-A, and TP165-B were identified as novel toluene transformation products, providing new possible evidence for additional degradation pathways, which could give new insights into the fate of toluene and phenol during the natural attenuation process in the environment. Finally, salicylaldehyde, 4-OH-benzaldehyde, and 4-OH-benzoic acid which were detected at Level 1 identification confidence were suggested as indicator chemicals of toluene and phenol exposure in the contaminated field.

Mn2O3/γ-Al2O3 catalysts synergistic double dielectric barrier discharge (DDBD) degradation of toluene, ethyl-acetate and acetone

Mn₂O₃/γ-Al₂O₃ catalysts was combined with double dielectric barrier discharge (DDBD) for degradation of acetone, toluene and ethyl acetate. Mn₂O₃/γ-Al₂O₃ catalysts with different Mn loading were synthesized by hydrothermal method. XRD, SEM, XPS and H₂-TPR were applied to characterize the catalysts. Among the catalysts prepared, the Mn₂O₃/γ-Al₂O₃ catalysts with 5 wt% Mn loading presented the best performance in multicomponent VOCs degradation, which the highest removal efficiency (58.8% for acetone, 96.3% for toluene and 85.8% for ethyl acetate), the best carbon balance (87.5%) and CO₂ selectivity (51.9%) were obtained at a specific input energy (SIE) of 700 J L^-1. The formation of ozone was obviously inhibited with the introduction of Mn₂O₃/γ-Al₂O₃ catalysts. The higher Mn³⁺/Mn ratio, higher O₂/O^2- ratio and excellent low-temperature reducibility were beneficial for the VOCs degradation. Highly dispersed Mn₂O₃ crystals on the surface of γ-Al₂O₃ also might be an explanation for the improvement of VOCs degradation. According to the result of GC-MS, the variety of organic by-products gradually decreased with the increase of SIE, and the degradation mechanism of the mixed VOCs in plasma and on catalyst surface was discussed.

A fixed-film bioscrubber of Microbacterium esteraromaticum SBS1-7 for toluene/styrene biodegradation

In the present study, a fixed-film bioscrubber (FFBS) of BTEX-degrading bacterium Microbacterium esteraromaticum SBS1-7 with 'AQUAPOROUSGEL® or APG' supporting material was continuously fed with toluene- or styrene-contaminated gas stream for 172 days. Response Surface Methodology (RSM) was used to optimize the biofilm formation on APG as well as the toluene biodegradation in mineral salt medium (MM). The results suggested that 1000 ppm of yeast extract (YE) was necessary for biofilm formation of SBS1-7. The optimized combination of YE and toluene concentration exhibiting the highest biofilm formation and toluene removal was further employed in an up-scale FFBS operation. The maximum Elimination Capacity (EC_max) of 203 g·m^-3·h^-1 was obtained at the toluene Inlet Loading Rate (ILR) of 295 g·m^-3·h^-1. FFBS of SBS1-7 was able to withstand a 5-day shutdown and required only 24 h to recover. Moreover, when the inlet Volatile Organic Compound was shifted to styrene, FFBS required only 24 h for adaptation and the system was able to efficiently remove ~95% of styrene after that. Finally, the performance of the bioscrubber when operated in 2 different modes of operation (FFBS vs Biotricking Filter or BTF) were compared. This study evidently demonstrated the robustness and stability of FFBS with M. esteraromaticum SBS1-7.

Biodegradation of polystyrene by deep-sea Bacillus paralicheniformis G1 and genome analysis

Polystyrene (PS) films were subjected to in vitro biodegradation by Bacillus paralicheniformis G1 (MN720578) isolated from 3538 m depth sediments of the Arabian Sea. The growth of the isolate was most favourable at pH 7.5, 30 °C and 4% salinity. A series of batch experiments were conducted to investigate the degradation of PS films up to 60 days. The results of this study indicated that the strain degraded 34% of PS film within 60 days of incubation. The complete genome sequence consists of 4,281,959 bp with 45.88% GC content and encodes 4213 protein coding genes. A high number of genes encoding monooxygenase, dioxygenase, peroxidase, esterase and hydrolase involved in the degradation of synthetic polymers were identified. Also genes associated with flagellum dependent motility, chemotaxis, biofilm formation and siderophores biosynthesis were identified in this deep-sea strain G1. This study suggests that B. paralicheniformis G1 could be a potential species for degradation of PS and its genome analysis provides insight into the molecular basis of biodegradation.

Transcriptomic Analysis for the Identification of Metabolic Pathway Genes Related to Toluene Response in Ardisia pusilla

Toluene is an industrial raw material and solvent that can be found abundantly in our daily life products. The amount of toluene vapor is one of the most important measurements for evaluating air quality. The evaluation of toluene scavenging ability of different plants has been reported, but the mechanism of plant response to toluene is only partially understood. In this study, we performed RNA sequencing (RNA-seq) analysis to detect differential gene expression in toluene-treated and untreated leaves of Ardisiapusilla. A total of 88,444 unigenes were identified by RNA-seq analysis, of which 49,623 were successfully annotated and 4101 were differentially expressed. Gene ontology analysis revealed several subcategories of genes related to toluene response, including cell part, cellular process, organelle, and metabolic processes. We mapped the main metabolic pathways of genes related to toluene response and found that the differentially expressed genes were mainly involved in glycolysis/gluconeogenesis, starch and sucrose metabolism, glycerophospholipid metabolism, carotenoid biosynthesis, phenylpropanoid biosynthesis, and flavonoid biosynthesis. In addition, 53 transcription factors belonging to 13 transcription factor families were identified. We verified 10 differentially expressed genes related to metabolic pathways using quantitative real-time PCR and found that the results of RNA-seq were positively correlated with them, indicating that the transcriptome data were reliable. This study provides insights into the metabolic pathways involved in toluene response in plants.

A metabolic investigation of arterialized venous flaps in rabbits using mass spectrometry-based metabolomics

An arterialized venous flap (AVF) is an ideal choice of flap to repair wounds. However, the survival of these flaps remains the source of some concern. This study used metabolomic analysis to investigate the mechanisms underlying survival in AVF flaps in order to guide the clinical application of these flaps. Thirty-six male Japanese rabbits were randomly divided into a sham group and an AVF group. They were used for histology and hemodynamic investigations. Three days after surgery, tissue samples were analyzed by mass spectroscopy-based metabolomics. The results of the study revealed a reduction in blood flow, infiltration of inflammatory cells, and necrosis of flaps in the AVF group. In addition, notable changes were evident in the levels of several metabolites in the AVF group, including lactic acid, acetoacetic acid, inositol phosphate, arachidonic acid, and other metabolites. Our results indicate that the AVF group experienced changes in several biological pathways, including energy metabolism, cell membrane stability, and inflammatory response. There is a significant metabolic difference between AVFs and physiological flaps. The dysregulation in certain metabolites may be related to the specific hemodynamics and insufficient energy metabolism of the AVFs.

Bacterial Biodiversity of Extra Virgin Olive Oils and Their Potential Biotechnological Exploitation

Bacterial diversity of 15 extra virgin olive oils, obtained from different Italian varieties, including Frantoio, Coratina, Bosana, and Semidana, was analyzed in this study. All bacterial isolates were genotyped using RAPD and REP-PCR method and grouped by means of cluster analyses. Sequencing of 16S rDNA of 51 isolates, representative of 36 clusters, led to the identification of Bacillus spp., Brevibacillus spp., Micrococcus spp., Staphylococcus spp., Pantoea spp., Kocuria spp., Lysinbacillus spp., and Lactobacillus spp., most of which reported for first time in olive oils. Phenotypic characterization of the 51 isolates, some of which ascribed to potentially probiotic species, indicate that two of them have beta-glucosidase activity while 37% present lipolytic activity. Preliminary evaluation of probiotic potential indicates that 31% of the isolates show biofilm formation ability, 29% acidic pH resistance, and 25% bile salt resistance. Finally, 29% of the isolates were sensitive to antibiotics while the remaining 71%, that include bacterial species well-recognized for their ability to disseminate resistance genes in the environment, showed a variable pattern of antibiotic resistance. The results obtained underline that microbial diversity of extra virgin olive oils represents an unexpected sink of microbial diversity and poses safety issues on the possible biotechnological exploitation of this microbial biodiversity.

Search for new cultured lipophilic bacteria in industrial fat-containing wastes

Fat-containing wastes that are generated as a result of industrial production of food products and are being accumulated in large quantities in wastewater and sewage treatment plants and present a serious environmental problem. Microorganisms that decompose various types of lipids may be potential candidates for creation of commercial bioformulations for fat destruction. The aim of the study was to obtain pure cultures of lipophilic bacteria from fat-containing wastes, to study their diversity and activity for the development of a biological product. As a result, 30 strains of different phylogenetic groups with lipolytic activity was obtained. The most isolated strains were represented by enterobacteria and pseudomonas members within the Gammaproteobacteria. Almost half of the isolated strains were closely related to conditionally pathogenic microorganisms such as Serratia, Klebsiella etc. Non-pathogenic strains and promising for biotechnology ones belonged to Pseudomonas citronellolis, P. nitroreducens, P. synxantha, P. extremaustralis, Bacillus subtilis, B. amyloliquefaciens, Brevibacillus brevis and Microvirgula sp.