Essential oil components of turmeric inhibit hepatic lipidification and liver fibrosis in a diet-induced NASH model rats.

In this study, the fraction extracted from turmeric powder with 50% ethanol and fractionated with n-hexane were administered to diet-induced NASH model rats. NASH model was prepared with SD rats by feeding an originally designed choline-deficient, high-fat, high-fructose (HFF-CD) diet for 10 weeks. To the HFF-CD diet, hexane fraction and 50% ethanol fraction after hexane fractionation were added at 100 mg/kg body weight. 10 weeks later, blood samples and liver were collected for the following parameters: lipid weights, serum ALT, AST, TG, liver TG, TBARS levels, lipid metabolism-related gene expression and histopathological examination of the liver. As the results, the hexane fraction and 50% ethanol fraction showed a decrease in lipid weight, a decrease in hepatic TG, and activation of PPAR-α in the lipid metabolism-related gene test. These results suggest that the hexane fraction of turmeric has an inhibitory effect on fat accumulation in the liver by promoting lipid metabolism in NASH model rats.

Asparagus falcatus L. (Asparagaceae) leaf extracts attenuate doxorubicin-induced renal toxicity via antioxidant, anti-inflammatory, and anti-apoptotic pathways.

The search for therapeutic agents that improve kidney function against doxorubicin-induced renal toxicity is important. Herein, the potential nephroprotective activity by Asparagus falcatus L. (AF, Asparagaceae) leaf extracts against doxorubicin-induced renal toxicity (5 mg/kg, ip) in Wistar rats (n = 6/group) after oral administration of hexane (55 mg/kg), ethyl acetate (35 mg/kg), butanol (75 mg/kg), and aqueous (200 mg/kg) extracts of AF for 28 consecutive days was investigated. It was noticed that the treatment with the selected extracts of AF significantly attenuated doxorubicin-induced elevations of serum creatinine, urea nitrogen, ß2-microglobulin, cystatin C, and proteinuria in experimental rats. The histology showed attenuation of the features of acute tubular injury. Treatment regimens significantly reversed the doxorubicin-induced reduction in total antioxidant status, glutathione peroxidase, and glutathione reductase activity in renal tissue homogenates. A suppression in lipid peroxidation was noted with hexane, ethyl acetate, and butanol extracts of AF. Moreover, a reduction in the concentration of the pro-inflammatory mediator TNF-α (p < 0.05), and immunohistochemical expression of COX-2 were observed. The immunohistochemical expression of pro-apoptotic Bax protein was decreased and the anti-apoptotic BCL-2 was increased in renal tissues following the treatments. In conclusion, it was revealed that, hexane, ethyl acetate, butanol, and aqueous extracts of AF attenuate doxorubicin-induced renal toxicity in Wistar rats through antioxidant, anti-inflammatory, and anti-apoptotic pathways. The plant, AF could be recommended as a promising therapeutic agent to minimize renal toxicity induced by doxorubicin in cancer patients, however, subsequent clinical trials are warranted.

Permixon®, hexane-extracted Serenoa repens, inhibits human prostate and bladder smooth muscle contraction and exerts growth-related functions in human prostate stromal cells.

AIMS: Recently, the European Association of Urology recommended hexane-extracted fruit of Serenoa repens (HESr) in their guidelines on management of non-neurogenic male lower urinary tracts symptoms (LUTS). Despite previously lacking recommendations, Permixon® is the most investigated HESr in clinical trials, where it proved effective for male LUTS. In contrast, underlying mechanisms were rarely addressed and are only marginally understood. We therefore investigated effects of Permixon® on human prostate and detrusor smooth muscle contraction and on growth-related functions in prostate stromal cells. MAIN METHODS: Permixon® capsules were dissolved using n-hexane. Contractions of human prostate and detrusor tissues were induced in organ bath. Proliferation (EdU assay), growth (colony formation), apoptosis and cell death (flow cytometry), viability (CCK-8) and actin organization (phalloidin staining) were studied in cultured human prostate stromal cells (WPMY-1). KEY FINDINGS: Permixon® inhibited α1-adrenergic and thromboxane-induced contractions in prostate tissues, and methacholine-and thromboxane-induced contractions in detrusor tissues. Endothelin-1-induced contractions were not inhibited. Neurogenic contractions were inhibited in both tissues in a concentration-dependent manner. In WPMY-1 cells, Permixon® caused concentration-dependent breakdown of actin polymerization, inhibited colony formation, reduced cell viability, and proliferation, without showing cytotoxic or pro-apoptotic effects. SIGNIFICANCE: Our results provide a novel basis that allows, for the first time, to fully explain the ubiquitous beneficial effects of HESr in clinical trials. HESr may inhibit at least neurogenic, α1-adrenergic and thromboxane-induced smooth muscle contraction in the prostate and detrusor, and in parallel, prostate stromal cell growth. Together, this may explain symptom improvements by Permixon® in previous clinical trials.

Simultaneous degradation of n-hexane and production of biosurfactants by Pseudomonas sp. strain NEE2 isolated from oil-contaminated soils.

The presence of surfactants in biofilters could enhance hydrophobic VOC removal. In this study, blood agar plate, methylene blue agar plate and a culture with n-hexane as the only carbon source were used to screen strains that could biodegrade n-hexane and produce biosurfactants simultaneously. The effects of n-hexane concentration on n-hexane removal and biosurfactant production were also investigated. Results showed that such a strain identified to be Pseudomonas sp. Strain NEE2 was successfully isolated from oil-polluted soils. The biosurfactants production by this strain were dependent on the initial concentration of n-hexane (132-2640 mg/L). At the concentration of 2640 mg/L of n-hexane, the biosurfactants promoted n-hexane removal. At 132 mg/L of n-hexane, n-hexane removal efficiency on day 2 exceeded 60%. The synergistic mechanisms of n-hexane removal and biosurfactant production by Pseudomonas sp. Strain NEE2 were discussed including the enhanced mass transfer from gas to liquid phase, within the biofilm phase and biodegradation at the presence of biosurfactants as well as the consequently enhanced production of the biosurfactants. These results in this study proved that it is possible for microorganisms utilizing the synergistic effect of hydrophobic VOC degradation and biosurfactant production for cost-effective hydrophobic VOC removal in biofilters.

Methanogenic biodegradation of paraffinic solvent hydrocarbons in two different oil sands tailings.

Microbial communities drive many biogeochemical processes in oil sands tailings and cause greenhouse gas emissions from tailings ponds. Paraffinic solvent (primarily C5-C6; n- and iso-alkanes) is used by some oil sands companies to aid bitumen extraction from oil sands ores. Residues of unrecovered solvent escape to tailings ponds during tailings deposition and sustain microbial metabolism. To investigate biodegradation of hydrocarbons in paraffinic solvent, mature fine tailings (MFT) collected from Albian and CNRL ponds were amended with paraffinic solvent at ~0.1wt% (final concentration: ~1000mgL-1) and incubated under methanogenic conditions for ~1600d. Albian and CNRL MFTs exhibited ~400 and ~800d lag phases, respectively after which n-alkanes (n-pentane and n-hexane) in the solvent were preferentially metabolized to methane over iso-alkanes in both MFTs. Among iso-alkanes, only 2-methylpentane was completely biodegraded whereas 2-methylbutane and 3-methylpentane were partially biodegraded probably through cometabolism. 16S rRNA gene pyrosequencing showed dominance of Anaerolineaceae and Methanosaetaceae in Albian MFT and Peptococcaceae and co-domination of "Candidatus Methanoregula" and Methanosaetaceae in CNRL MFT bacterial and archaeal communities, respectively, during active biodegradation of paraffinic solvent. The results are important for developing future strategies for tailings reclamation and management of greenhouse gas emissions.

Comparative investigation on a hexane-degrading strain with different cell surface hydrophobicities mediated by starch and chitosan.

Bioremediation usually exhibits low removal efficiency toward hexane because of poor water solubility, which limits the mass transfer rate between the substrate and microorganism. This work aimed to enhance the hexane degradation rate by increasing cell surface hydrophobicity (CSH) of the degrader, Pseudomonas mendocina NX-1. The CSH of P. mendocina NX-1 was manipulated by treatment with starch and chitosan solution of varied concentrations, reaching a maximum hydrophobicity of 52%. The biodegradation of hexane conformed to the Haldane inhibition model, and the maximum degradation rate (ν max) of the cells with 52% CSH was 0.72 mg (mg cell)-1·h-1 in comparison with 0.47 mg (mg cell)-1·h-1 for cells with 15% CSH. The production of CO2 by high CSH cells was threefold higher than that by cells at 15% CSH within 30 h, and the cumulative rates of O2 consumption were 0.16 and 0.05 mL/h, respectively. High CSH was related to low negative charge carried by the cell surface and probably reduced the repulsive electrostatic interactions between hexane and microorganisms. The FT-IR spectra of cell envelopes demonstrated that the methyl chain was inversely proportional to increasing CSH values, but proteins exhibited a positive effect to CSH enhancement. The ratio of extracellular proteins and polysaccharides increased from 0.87 to 3.78 when the cells were treated with starch and chitosan, indicating their possible roles in increased CSH.

Sequential biodegradation of complex naphtha hydrocarbons under methanogenic conditions in two different oil sands tailings.

Methane emissions in oil sands tailings ponds are sustained by anaerobic biodegradation of unrecovered hydrocarbons. Naphtha (primarily C6-C10; n- iso- and cycloalkanes) is commonly used as a solvent during bitumen extraction process and its residue escapes to tailings ponds during tailings deposition. To investigate biodegradability of hydrocarbons in naphtha, mature fine tailings (MFT) collected from Albian and CNRL tailings ponds were amended with CNRL naphtha at ∼0.2 wt% (∼2000 mg L-1) and incubated under methanogenic conditions for ∼1600 d. Microbial communities in both MFTs started metabolizing naphtha after a lag phase of ∼100 d. Complete biodegradation/biotransformation of all n-alkanes (except partial biodegradation of n-octane in CNRL MFT) followed by major iso-alkanes (2-methylpentane, 3-methylhexane, 2- and 4-methylheptane, iso-nonanes and 2-methylnonane) and a few cycloalkanes (derivatives of cyclopentane and cyclohexane) was observed during the incubation. 16S rRNA gene pyrosequencing showed dominance of Peptococcaceae and Anaerolineaceae in Albian MFT and Anaerolineaceae and Syntrophaceae in CNRL MFT bacterial communities with co-domination of Methanosaetaceae and "Candidatus Methanoregula" in archaeal populations during active biodegradation of hydrocarbons. The findings extend the known range of hydrocarbons susceptible to methanogenic biodegradation in petroleum-impacted anaerobic environments and help refine existing kinetic model to predict greenhouse gas emissions from tailings ponds.

Long-Term Incubation Reveals Methanogenic Biodegradation of C5 and C6 iso-Alkanes in Oil Sands Tailings.

iso-Alkanes are major components of petroleum and have been considered recalcitrant to biodegradation under methanogenic conditions. However, indigenous microbes in oil sands tailings ponds exposed to solvents rich in 2-methylbutane, 2-methylpentane, 3-methylpentane, n-pentane, and n-hexane produce methane in situ. We incubated defined mixtures of iso- or n-alkanes with mature fine tailings from two tailings ponds of different ages historically exposed to different solvents: one, ~10 years old, receiving C5-C6 paraffins and the other, ~35 years old, receiving naphtha. A lengthy incubation (>6 years) revealed iso-alkane biodegradation after lag phases of 900-1800 and ~280 days, respectively, before the onset of methanogenesis, although lag phases were shorter with n-alkanes (~650-1675 and ~170 days, respectively). 2-Methylpentane and both n-alkanes were completely depleted during ~2400 days of incubation, whereas 2-methylbutane and 3-methylpentane were partially depleted only during active degradation of 2-methylpentane, suggesting co-metabolism. In both cases, pyrotag sequencing of 16S rRNA genes showed codominance of Peptococcaceae with acetoclastic (Methanosaeta) and hydrogenotrophic (Methanoregula and Methanolinea) methanogens. These observations are important for predicting long-term greenhouse-gas emissions from oil sands tailings ponds and extend the known range of hydrocarbons susceptible to methanogenic biodegradation in petroleum-impacted anaerobic environments.

Biodegradation of oil spill by petroleum refineries using consortia of novel bacterial strains.

Feasibility study carried out at the site prior to the full scale study showed that the introduced bacterial consortium effectively adapted to the local environment of the soil at bioremediation site. The soil samples were collected from the contaminated fields after treatment with bacterial consortium at different time intervals and analyzed by gas chromatography after extraction with hexane and toluene. At time zero (just before initiation of bioremediation), the concentration of total petroleum hydrocarbons in the soil (25-cm horizon) of plot A, B, C and D was 30.90 %, 18.80 %, 25.90 % and 29.90 % respectively, after 360 days of treatment with microbial consortia was reduced to 0.97 %, 1.0 %, 1.0 %, and 1.1 % respectively. Whereas, only 5 % degradation was observed in the control plot after 365 days (microbial consortium not applied).

Biodegradation of methyl tert-butyl ether by cometabolism with hexane in biofilters inoculated with Pseudomonas aeruginosa.

Biodegradation of methyl tert-butyl ether (MTBE) vapors by cometabolism with gaseous hexane (n-hexane > 95%) was investigated using Pseudomonas aeruginosa utilizing short chain aliphatic hydrocarbon (C(5)-C(8)). Kinetic batch experiments showed that MTBE was degraded even when hexane was completely exhausted with a cometabolic coefficient of 1.06 ± 0.16 mg MTBE mg hexane(-1). Intermediate tert-butyl alcohol (TBA) accumulation was observed followed by its gradual consumption. A maximum MTBE elimination capacity (EC(MAX)) of 35 g m(-3) h(-1) and removal efficiency (RE) of 70% were attained in mineral medium amended biofilters having an empty bed residence time (EBRT) of 1 min. For these experimental conditions, a maximum hexane EC of approximately 60 g m(-3) h(-1) was obtained at a load of 75 g m(-3) h(-1). Experiments under transient conditions revealed a competitive substrate interaction between MTBE and hexane. Biomass densities between 5.8 and 12.6 g L(biofilter) (-1) were obtained. Nevertheless, production of biopolymers caused non-uniform distribution flow rates that reduced the performance. Residence time distribution profiles showed an intermediate dispersion flow rate with a dispersion coefficient of 0.8 cm(2) s(-1).

Identification of a eukaryotic reductive dechlorinase and characterization of its mechanism of action on its natural substrate.

Chlorinated compounds are important environmental pollutants whose biodegradation may be limited by inefficient dechlorinating enzymes. Dictyostelium amoebae produce a chlorinated alkyl phenone called DIF which induces stalk cell differentiation during their multicellular development. Here we describe the identification of DIF dechlorinase. DIF dechlorinase is active when expressed in bacteria, and activity is lost from Dictyostelium cells when its gene, drcA, is knocked out. It has a K(m) for DIF of 88 nM and K(cat) of 6.7 s(-1). DrcA is related to glutathione S-transferases, but with a key asparagine-to-cysteine substitution in the catalytic pocket. When this change is reversed, the enzyme reverts to a glutathione S-transferase, thus suggesting a catalytic mechanism. DrcA offers new possibilities for the rational design of bioremediation strategies.

Biological treatment of mixtures of toluene and n-hexane vapours in a hollow fibre membrane bioreactor.

Membrane bioreactors are gaining interest for the control of contaminated air streams. In this study, the removal of toluene and n-hexane vapours in a hollow fibre membrane bioreactor (HFMB) was investigated. The focus was on quantifying the possible interactions occurring during the simultaneous biotreatment of the two volatile pollutants. Two lab-scale units fitted with microporous polypropylene hollow fibre membranes were connected in series and inoculated with activated sludge. Contaminated air was passed through the lumen at gas residence times ranging from 2.3 to 9.4 s while a pollutant-degrading biofilm developed on the shell side of the fibres. When toluene was treated alone, very high elimination capacities (up to 750 g m(-3) h(-1) based on lumen volume, or 1.25 g m(-2) h(-1) when normalized by the hollow fibre membrane area) were reached. When toluene and hexane were treated simultaneously, toluene biodegradation was partially inhibited by n-hexane, resulting in lower toluene removal rates. On the other hand, hexane removal was only marginally affected by the presence of toluene and was degraded at very high rates (upwards of 440 g m(-3) h(-1) or 0.73 g m(-2) h(-1) without breakthrough). Overall, this study demonstrates that mixtures of toluene and n-hexane vapours can be effectively removed in hollow fibre membrane bioreactors and that complex biological interactions may affect one or more of the pollutants undergoing treatment in gas-phase membrane bioreactors.

Antioxidant and anti-inflammatory effects of Scoparia dulcis L.

Different extracts were obtained from Scoparia dulcis L. (Scrophulariaceae) by successive extraction with hexane, chloroform, and methanol. These extracts exhibited significant antioxidant capacity in various antioxidant models mediated (xantine oxidase and lipoxygenase) or not mediated (2,2-diphenyl-picrylhydrazyl, ferric-reducing antioxidant power, ß-carotene bleaching, lipid peroxidation) by enzymes. The antioxidant activity of the extracts was related to their phytochemical composition in terms of polyphenol and carotenoid contents. The chloroform extract was richest in phytochemicals and had the highest antioxidant activity in the different antioxidant systems. All the extracts exhibited less than 50% inhibition on xanthine oxidase but more than 50% inhibition on lipid peroxidation and lipoxygenase. The extracts strongly inhibited lipid peroxidation mediated by lipoxygenase.

[Effects of garlic oil, age and sex on n-hexane metabolism in rats].

OBJECTIVE: To investigate effects of garlic oil (GO), age and sex on n-hexane metabolism in rats. METHODS: The Wistar rats were used as experimental animals. (1) Intragastric administration: n-hexane group (3000 mg/kg n-hexane), GO treated group (80 mg/kg GO ig. an hour earlier than 3000 mg/kg n-hexane), then blood was taken from tails of rats at 8, 12, 16, 20, 24, 28, 32 h points after n-hexane administration. (2) Intraperitoneal injection: n-hexane group (1000 mg/kg n-hexane), GO treated group (80 mg/kg GO ig. an hour earlier than 1000 mg/kg n-hexane), then took blood was taken from tails of rats at 8, 12, 16, 20, 24, 28 h points after n-hexane injection. (3) 7 rats each group of 6, 8, 10 weeks age were administrated by 3000 mg/kg n-hexane intragastrically, then were taken blood from tails at 16, 20, 24 h points after administration. (4) 7 male and 7 female rats of 8 weeks age were administrated by 3000 mg/kg n-hexane intragastrically, then were taken blood from tails at 16, 20, 24, 28 h points after administration. The gas chromatography was used to determine the metabolite 2, 5-hexanedione concentration of n-hexane in serum and 2, 5-hexanedione concentration was compared between GO and no GO treated rats, different ages and different sexes. RESULTS: (1) Intragastric administration: 2, 5-hexanedione concentrations in serum of n-hexane group and GO treated group had the peak 19.2 and 12.3 µg/ml at 20h and 24 h points. Compared with n-hexane group, the serum 2, 5-hexanedione concentration of GO treated group was lower at time points prior to peak and 2, 5-hexanedione eliminating process was slower after peak. (2) Intraperitoneal injection: effects of GO on the serum 2, 5-hexanedione concentrations was very similar to intragastric administration, 2, 5-hexanedione concentrations in serum of n-hexane group and GO treated group had the peak 15.0 and 6.7 µg/ml at 12 h and 16 h points. (3) Comparison of the serum 2, 5-hexanedione concentrations of different weeks age rats: The serum 2, 5-hexanedione concentrations of 6, 8, 10 weeks age rats were 25.5, 15.0, 12.8 µg/ml each (8, 10 weeks age significantly lower than 6 weeks age) at 16 h point; at 20 h point, they were 24.7, 18.3, 15.0 µg/ml each (10 weeks age significantly lower than 6 weeks age); at 24 h point, they were 11.0, 14.7, 8.1 µg/ml each (10 weeks age significantly lower than 8 weeks age). (4) Comparisons of the serum 2, 5-hexanedione concentrations of different sex rats: the serum 2, 5-hexanedione concentrations of male and female rats were 22.5, 17.2 µg/ml each at 16 h point (different significantly); at 20, 24, 28 h points, they were 27.6, 22.9 µg/ml, 24.6, 19.1 µg/ml, 19.1, 13.8 µg/ml each (different non-significantly). CONCLUSION: GO reduces production of 2, 5-hexanedione in serum generated by n-hexane in rats; the metabolic capacity of low age rats on n-hexane is stronger than high age ones.

Effect of surfactant and oil additions in the biodegradation of hexane and toluene vapours in batch tests.

The biological treatment of gaseous emissions of hydrophobic volatile organic compounds (VOCs) results in low rates of elimination partially because of the low solubility of VOCs in water. Recently, the use of two-phase partition bioreactors (TPPBs) was proposed to increase the bioavailability and consequently the elimination capacities of this kind of VOC. In the present study, TPPBs operating in a batch feed mode were tested for biodegradation of hexane and toluene vapours with a microbial consortium. The results obtained were compared with single-phase systems (control experiments). The liquid phase used was silicone oil (organic phase) with the surfactant Pluronic F-68. Experiments were named F1 and F2 for one and two phases, respectively, and F(1S) and F(2S) when the surfactant was included. The maximum specific rates (S(rates)) of hydrocarbon consumption for hexane and toluene were 539 and 773 mg(hydrocarbon)/(g(protein) x h), respectively. For both substrates, the systems that showed the highest S(rates) of hydrocarbon consumption were F2 and F(2S). In experiment F(1S) the surfactant Pluronic F-68 increased the solubility of hydrocarbons in the liquid phase, but did not increase the S(rates). The maximum percentages of mineralization were 51% and 72% for hexane and toluene, respectively. The results showed that simultaneous addition of silicone oil and surfactant favours the mineralization, but not the rate ofbiodegradation, of toluene and hexane vapours.

Treatment of dynamic mixture of hexane and benzene vapors in a Trickle Bed Air Biofilter integrated with cyclic adsorption/desorption beds.

One of the main challenges that face successful biofiltration is the erratic loading pattern and long starvation periods. However, such patterns are common in practical applications. In order to provide long-term stable operation of a biofilter under these conditions, a cyclic adsorption/desorption beds system with flow switching was installed prior to a biofilter. Different square waves of a mixture containing n-hexane and benzene at a 2:1 ratio were applied to the cyclic adsorption/desorption beds and then fed to a biofilter. The performance of this integrated system was compared to a biofilter unit receiving the same feed of both VOCs. The cyclic adsorption/desorption beds unit successfully achieved its goal of stabilizing erratic loading even with very sharp peaks at the influent concentration equalizing influent concentrations ranging from 10-470 ppmv for n-hexane to 30-1410 ppmv for benzene. The study included different peak concentrations with durations ranging from 6 to 20 min. The cyclic beds buffered the fluctuating influent load and the followed biofilter had all the time a continuous stable flow. Another advantage achieved by the cyclic adsorption/desorption beds was the uninterrupted feed to the biofilter even during the starvation where there was no influent in the feed. The results of the integrated system with regard to removal efficiency and kinetics are comparable to published results with continuous feed studies at the same loading rates. The removal efficiency for benzene had a minimum of 85% while for n-hexane ranged from 50% to 77% according to the loading rate. The control unit showed very erratic performance highlighting the benefit of the utilization of the cyclic adsorption/desorption beds. The biofilter was more adaptable to concentration changes in benzene than n-hexane.

The engagement of selectins and their ligands in colorectal cancer liver metastases.

he colonization of the liver by colorectal cancer (CRC) cells is a complicated process which includes many stages, until macrometastases occur. The entrapment of malignant cells within the hepatic sinusoids and their interactions with resident non-parenchymal cells are considered very important for the whole metastatic sequence. In the sinusoids, cell connection and signalling is mediated by multiple cell adhesion molecules, such as the selectins. The three members of the selectin family, E-, P- and L-selectin, in conjunction with sialylated Lewis ligands and CD44 variants, regulate colorectal cell communication and adhesion with platelets, leucocytes, sinusoidal endothelial cells and stellate cells. Their role in CRC liver metastases has been investigated in animal models and human tissue, in vivo and in vitro, in static and shear flow conditions, and their key-function in several molecular pathways has been displayed. Therefore, trials have already commenced aiming to exploit selectins and their ligands in the treatment of benign and malignant diseases. Multiple pharmacological agents have been developed that are being tested for potential therapeutic applications.

Determination of 2,5-hexanedione in urine by headspace solid-phase microextraction and gas chromatography.

2,5-Hexanedione (2,5-HD) is the most important metabolite of n-hexane and methyl ethyl ketone in human urine. Urinary 2,5-HD is used as a biomarker for biological monitoring of workers exposed to n-hexane. A simple method using headspace solid-phase microextraction (HS-SPME) and gas chromatography (GC) equipped with a flame-ionization detector (FID) was developed. The parameters that affect the HS-SPME-GC-FID process were optimized (i.e., fiber coating, sample volume, adsorption and heating time, salt addition, and extraction temperature). The assay presented linearity in the range of 0.075 to 20.0 mg/L, precision (coefficient of variation < 7.0%), and detection limit of 0.025 mg/L for 2,5-HD in urine. The method was successfully applied to the analysis of 2,5-HD in urine samples from eight workers occupationally exposed to n-hexane in shoemaker's glue.

Fungal removal of gaseous hexane in biofilters packed with poly(ethylene carbonate) pine sawdust or peat composites.

The removal of volatile organic compounds (VOC) in biofilters packed with organic filter beds, such as peat moss (PM) and pine sawdust (PS), frequently presents drawbacks associated to the collapse of internal structures affecting the long-term operation. Poly(ethylene ether carbonate) (PEEC) groups grafted to these organic carriers cross linked with 4,4'-methylenebis(phenylisocyanate) (MDI) permitted fiber aggregation into specific shapes and with excellent hexane sorption performance. Modified peat moss (IPM) showed very favorable characteristics for rapid microbial development. Water-holding capacity in addition to hexane adsorption almost equal to the dry samples was obtained. Pilot scale hexane biofiltration experiments were performed with the composites after inoculation with the filamentous fungus Fusarium solani. During the operation of the biofilter under non-aseptic conditions, the addition of bacterial antibiotics did not have a relevant effect on hexane removal, confirming the role of fungi in the uptake of hexane and that bacterial growth was intrinsically limited by an adequate performance of the composites. IPM biofilter had a start-up period of 8-13 days with concurrent CO(2) production of approximately 90 g m(-3) h(-1) at day 11. The final pressure drop after 70 days of operation was 5.3 mmH(2)O m(-1) reactor. For modified pine sawdust (IPS) packed biofilter, 5 days were required to develop an EC of about 100 g m(-3) h(-1) with an inlet hexane load of approximately 190 g m(-3) h(-1). Under similar conditions, 12-17 days were required to observe a significant start-up in the reference perlite biofilter to reach gradually an EC of approximately 100 g m(-3) h(-1) at day 32. Under typical biofiltration conditions, the physical-chemical properties of the modified supports maintained a minimum water activity (a(w)) of 0.925 and a pH between 4 and 5.5, which allowed the preferential fungal development and limited bacterial growth.

Solid/gas biocatalysis: an appropriate tool to study the influence of organic components on kinetics of lipase-catalyzed alcoholysis.

The influence of the addition of an extra component in a gaseous reaction medium, on the kinetics of alcoholysis of methyl propionate and n-propanol catalyzed by immobilized lipase B from Candida antarctica was studied in a continuous solid/gas reactor. In this reactor, the solid phase is composed of a packed enzymatic sample, which is percolated by gaseous nitrogen, simultaneously carrying gaseous substrates and additional components to the enzyme while removing reaction products. The system permits to set thermodynamic activity of all gaseous components (substrates or not) independently at the desired values. This allows in particular to study the influence of an extra added component at a constant thermodynamic activity value, contrary to classical solid/liquid system, which involves large variations of thermodynamic activity of added solvent, when performing full kinetic studies. Alcohol inhibition constant (K(I)) and methyl propionate and propanol dissociation constants (K(MP) and K(P)) have been determined in the solid/gas reactor in the presence of 2-methyl-2-butanol, and compared with values previously obtained in the absence of added component and in the presence of water. Complementary experiments were carried out in the presence of an apolar compound (hexane) and led to the conclusion that the effect of added organic component on lipase-catalyzed alcoholysis is related to their competitive inhibitory character towards first substrate methyl propionate. The comparison of data obtained in liquid or with gaseous 2-methyl-2-butanol shows that lower K(MP) and K(I) are found in gaseous medium, which would correspond on the one hand to a lower acylation rate k(2), and on the other hand to a higher binding rate k(1) between substrate and free enzyme in gaseous medium.