Concentrations Of N-butanol Research Articles

Room temperature n-butanol detection by Ag-modified In2O3 gas sensor with UV excitation

The aim of this study is to develop a sensor for the detection of n-butanol gas at room temperature, which in turn facilitates sensor integration. To this end, porous In2O3 nanosheets were prepared in this experiment, along with noble metal Ag modification and UV excitation, to achieve effective monitoring of low concentrations of n-butanol at room temperature. The material composition and structure were analyzed by various analysis techniques. The addition of precious metals promotes the absorption of UV light by the material. The n-butanol gas sensitivity test was completed on individual samples under 365 nm UV. The response of 5wt% Ag/In2O3 to 10 ppm n-butanol under UV irradiation reaches 127.5% at room temperature, which is twice as much as pure In2O3. The sensor showed a well regular answer at different concentrations of n-butanol. This paper also discusses the sensing mechanism for the improved gas-sensitive behavior of Ag/In2O3, which mainly benefits from the chemical and electron sensitizing of Ag. The results show that the Ag/In2O3 material excited by ultraviolet light in this paper lays a certain foundation for the preparation of room temperature n-butanol gas sensor.

Biofunctionalized magnetic nanoparticles incorporated MoS2 nanocomposite for enhanced n-butanol sensing at room temperature

N-butanol is well known to be a flammable and harmful liquid that is a potential threat to human health and property. Therefore, it is important to monitor the concentration of n-butanol in the surroundings. The need for highly efficient toxic gas detection is urgent and has been driving the research on gas sensors for practical applications. Molybdenum disulfide (MoS2) has been attracting significant interest for gas detection at room temperature. Herein, we report biofunctionalized magnetic nanoparticles incorporated MoS2 for sensing n-butanol. The biosynthesized magnetite nanoparticles (CT-Fe3O4) were synthesized by the addition of Cinnamomum Tamala (CT) leaf extract, and subsequently, the nanocomposite was synthesized using a hydrothermal method. Highly sensitive sensors based on MoS2-CT-Fe3O4 were fabricated and tested for sensing different concentrations of n-butanol. The nanocomposites showed a good sensing performance (Δ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Delta$$\\end{document} R/Rair %) of 72% towards 20 ppm of n-butanol, indicating the potential use of MoS2-CT-Fe3O4 nanocomposite for sensing n-butanol at room temperature.

Ag modified ZnO nanoflower gas sensitive sensor for selective detection of n-butanol

Ag modified ZnO nanoflowers were successfully prepared by sunlight induced solvent reduction method. The samples were characterized by x-ray diffractometer, field emission scanning electron microscope, transmission electron microscope and energy dispersive x-ray spectrum, and the results confirmed the presence of Ag nanoparticles on the ZnO nanoflower. The gas sensing performance of the materials was studied at different operating temperatures and different n-butanol concentrations. The results showed that the Ag modified ZnO nanoflower sensor responded to 50 ppm n-butanol up to 147.17 at 280 °C, and the Ag modified ZnO nanoflower sensor exhibited excellent repeatability, stability and response recovery time. In addition, different target gases were employed for the selectivity study of the Ag modified ZnO nanoflower. It can be found that the Ag modified ZnO nanoflower had good selectivity for n-butanol. The improved response of the Ag modified ZnO nanoflower sensor was attributed to the catalytic effect of Ag nanoparticles. The results indicate that the Ag modified ZnO nanoflower will become a very promising sensing material for n-butanol gas detection.

Effects of Dichloromethane and N-Butanol Fractions of Nigella sativa on ACHN and GP-293 Cell Line Morphology, Viability, and Apoptosis.

Renal cell carcinoma (RCC) is among the top death-causing cancers. Medicinal herbs can also have beneficial effects on RCC treatment. In this project, we aimed to study the antitumor effect of dichloromethane and N-butanol fractions of hydroalcoholic extract of Nigella sativa (N. sativa) on the morphology, viability, and apoptosis of ACHN (human renal adenocarcinoma) and GP-293 (normal renal epithelial) cell lines. In this experimental study, N-butanol and dichloromethane fractions of N. sativa were obtained, and ACHN and GP293 cell lines were treated with various concentrations of dichloromethane (0-100 μg/mL) and N-butanol (0-12.5 μg/mL) fractions for 24, 48, and 72 hours. Then, morphological changes, viability, and apoptosis were investigated. Our results indicated that dichloromethane and N-butanol fractions cause morphological changes and significant decreases in the percentage of live cells in the ACHN cell line, in a dose- and time-dependent manner. In the GP-293 cell line, however, a lower toxicity was observed in comparison with that found for ACHN. The results of flow cytometry showed an apoptotic effect of dichloromethane and N-butanol fractions on the ACHN cell line but a higher rate of apoptosis induction for the total extract compared to the two fractions in the renal cancer cell line compared to the normal cell line. Our findings demonstrated that these two fractions of N. sativa induce inhibitory effects on the ACHN cell line morphology and viability. These effects were lower than those induced by the total extract. In addition, the two fractions caused more marked effects in the renal cancer cell line compared with the GP-293 cell line.

Diesel blends with high concentrations of biodiesel and n-butanol: Effects on regulated pollutants and polycyclic aromatic hydrocarbons

Despite advances in alternative energy production (including electric vehicles and hydrogen fuel cells), fossil fuels remain ubiquitous and an ongoing threat to the environment. Alternative biofuels such as biodiesel and n-butanol have garnered substantial attention in recent years as additives to fossil diesel as a means to control emissions such as nitrous oxides (NOx) and carbon monoxide (CO). In addition, as biodiesel and alcohols do not contain aromatic hydrocarbons in their chemical structures, they provide potential additional advantages for reducing toxic emissions, including polycyclic aromatic hydrocarbons (PAHs); however, this is often only demonstrated for relatively low blend ratios (<20 %). In this study, the effects of neat diesel, waste oil biodiesel, and n-butanol blends on engine function, regulated, and unregulated emissions were investigated for blends containing 50/50 vol% diesel/biodiesel (D50B50), 50/25/25 vol% diesel/biodiesel/n-butanol (D50B25Bu25), and 50/50 vol% diesel/n-butanol (D50Bu50), in addition to neat standard road diesel (D100) and waste oil derived biodiesel (B100). In these blends NOx was reduced by up to 28.1 % relative to D100 for loads above idle, while increasing exhaust gas temperatures up to 33.5 % and increasing unburned hydrocarbons (HC) and CO by up to 84.2 % and 93.8 %, respectively. Measured against neat diesel, biodiesel and the diesel-biodiesel-butanol blend reduced PAH toxicity by up to 46.4 %, while diesel-biodiesel and diesel-butanol blends showed an increase up to 14.3% and 504%, respectively, due to higher concentrations of 5-ring PAHs. It has been concluded that in addition to fuel aromaticity, other factors such as fuel properties affecting the diesel combustion process (i.e. cetane number), can cause PAH formation.

HIGH-PERFORMANCE THIN-LAYER CHROMATOGRAPHY (HPTLC) METHOD DEVELOPMENT AND VALIDATION FOR DETERMINATION OF REMOGLIFLOZIN ETABONATE AND VILDAGLIPTIN IN BULK AND ITS TABLET FORMULATION

Objective: Within the scope of this investigation, an HPTLC technique for measuring the concentrations of Remogliflozin etabonate (REMO) and Vildagliptin (VIL) in a commercial product named REMO-V, which contains 100 mg of REMO and 50 mg of Vildagliptin (VIL), was developed. Methods: It was necessary to evaluate the new approach for linearity, precision, specificity, and robustness in order to ensure that it operated properly. The chromatograms were created using a mobile phase containing Chloroform as follows: The concentrations of toluene, methanol, and n-butanol (4.5:4:1:0.5, v/v) were measured on a pre-coated TLC aluminum pre-coated plate (60F 254), and the absorbance at 233 nm was used to determine the amount of each component present. It was necessary to conduct forced degradation testing on bulk medicinal material in order to demonstrate the new method's capacity to demonstrate how stable and specific it is. Results: The Rf values for Remogliflozin etabonate (0.63), Vildagliptin (0.75), and Remogliflozin etabonate (0.63), respectively, were 0.63 and 0.75. On the REMO side, the linearity of the technique was found to be between 20 and 60 g/band; on the VIL side, it was found to be between 10 and 30 g/band. Having R2 values of 0.9939 for both REMO and VIL, it is clear that there is significant linearity in the way they interact with one another. These are the lower limits of detection and quantification for REMO, which were 0.09 for VIL and 0.38 for REMO, respectively, when compared to the upper limits of detection and quantification for VIL. The lower detection and quantification limits for VIL are also the same as for other pathogens. RSD was less than 2 percent in this study. Thus, the approach was shown to be accurate and exact for both interday and intraday accuracy, indicating that it is reliable. The amount of REMO or VIL that might be recovered is as follows: 98.7 percent to 101.27 percent, and 97.37 percent to 100.83 percent were the results. Conclusion: It was discovered that the method for determining Remogliflozin and Vildagliptin was easy, accurate, and stable in both its pure form and its tablet dose form and that it could be used to both (REMO-V, Glenmark, Ltd)

Room-temperature sensing performance of Pt nanoparticles modified In2O3@ZnS core-shell hollow nanospheres to n-butanol

Room-temperature detection is a great pursuit of goal for semiconductor sensors, aiming to lower energy consumption, prolong the lifetime of sensors, and mitigate safety risks. In this study, room-temperature sensing materials, made of novel Pt nanoparticles modified In2O3@ZnS core-shell hollow nanospheres (Pt-In2O3@ZnS CSHNs), were synthesized by simple hydrothermal and in-situ reduction methods without using any surfactants or toxic organic solvents. The effects of the morphology and composition on gas sensing performance were systematically investigated by adjusting the content of Pt nanoparticles. These materials exhibited excellent sensing performance towards n-butanol at (near) room temperature (~25 °C). The optimal working temperature of Pt-In2O3@ZnS CSHNs (50 °C) was decreased by 210 °C than that of In2O3@ZnS (1:1) CSHNs (260 °C) towards 100 ppm of n-butanol. In particular, the 5% Pt-In2O3@ZnS CSHNs showed an excellent sensing response towards different concentrations of n-butanol at room temperature. The highest sensing response of Pt-In2O3@ZnS CSHNs was up to 7.1 (at 50 °C) and 6.2 (at 25 °C) for 100 ppm n-butanol with a short response time. Further studies demonstrated that such enhanced performances were possibly owing to the “catalytic sensitization” effect driven by Pt NPs and the “electronic sensitization” effect triggered through the formation of Pt-ZnS Schottky junction and In2O3/ZnS n-n heterojunction. This study may shed light on promising gas sensing materials to achieve the room-temperature detection of n-butanol in practical application.

Dielectric Dispersion Response of Binary Mixtures of n-Butanol and Valeronitrile

Complex permittivity spectra of various concentrations (0.0 → 1.0) of n-Butanol and its mixtures with Valeronitrile were obtained in the radio and microwave frequency range (0.2 GHz to 20 GHz) using Vector network analyzer (VNA). Complex permittivity data points were fitted into Havriliak-Negami Model. CNLS fitting using LEVMW software used to obtain dielectric parameters. Excess static dielectric constant and excess inverse relaxation time for the binary mixtures were calculated and fitted in Redlich-Kister polynomial to derive the binary coefficients and standard deviations. Variation of these parameters were discussed in terms molecular interaction between molecular species.

One-dimensional In2O3 nanorods as sensing material for ppb-level n-butanol detection

Effectively and quantificationally detecting hazardous gas n-butanol is very significant in daily life, which can bring about a safe living condition for humans. In this study, the one-dimensional In2O3 nanorods were successfully synthesized via hydrothermal route and post-heat treatment. Noticeably, one-dimensional nanorods structures were obtained and the products presented a superior growth orientation along with (222) plane. Additionally, systematical gas-sensing measurements of the sensor made from In2O3 nanorods towards hazardous n-butanol gas were conducted. Results exhibited that the fabricated sensor showed excellent n-butanol sensing properties, with aspects to a superior response value of 342.20 with concentration 100 ppm at 240 °C, remarkable selectivity, fast response/recovery times (77.5/34.2 s) and good stability. More interestingly, the detection limit of sensor as low as 500 ppb and a good linearity relationship between response values and n-butanol concentrations was presented. Gas-sensitive properties of this sensor are better than previously reported in n-butanol detection. All results demonstrate that one-dimensional In2O3 nanorod is a promising sensor material to practical applications in effectively detecting n-butanol gas.

Combustion characteristics of compression ignition engine fuelled with rapeseed oil–diesel fuel–n-butanol blends

Liquid biofuels for compression ignition engines are often based on vegetable oils. In order to be used in compression ignition engine the vegetable oils have to be processed because of their high viscosity or it is also possible to use vegetable oils in fuel blends. In order to decrease the viscosity of the fuel blends containing crude vegetable oil the alcohol-based fuel admixtures can be used. The paper describes the effect of rapeseed oil–diesel fuel–n-butanol blends on combustion characteristics and solid particles production of turbocharged compression ignition engine. The 10% and 20% concentrations of n-butanol in the fuel blend were measured and analysed. The engine Zetor 1204, located in tractor Zetor Forterra 8641 with the power of 60kW and direct injection was used for the measurement. The engine was loaded through power take off shaft of the tractor using mobile dynamometer MAHA ZW500. The measurement was carried out in stabilized conditions at 20%, 60% and 100% engine load. The engine speed was kept at 1950 rpm. Tested fuel blends showed lower production of solid particles than diesel fuel and lower peak cylinder pressure and with increasing concentration of n-butanol in the fuel blend the ignition delay was prolonged and premixed phase of combustion was increased.

Calorimetric determination of the thermodynamics of alcohol-surfactant mixed micelle formation: Temperature and concentration effects

The thermodynamic parameters of surfactant/alcohol mixed micelles were determined in mixtures of sodium dodecyl sulfate (SDS) and dodecyltrimethylammonium bromide (DTAB) in a series of solvents composed of varying concentrations of n-propanol (C3OH), n-butanol (C4OH), and n-pentanol (C5OH). Conductivity studies were used to determine CMC values and the degrees of counterion binding. Isoperibol solution calorimetry was used to directly determine CMC values and enthalpy of micellization (ΔmicH). From these experimentally determined values, the Gibbs energy and entropy of micellization were calculated as a function of temperature and alcohol concentration. In general, CMC values decreased with increasing alcohol carbon chain length and concentration but increased with temperature. The effects of temperature, alcohol carbon chain length, and alcohol concentration on the energetics of these mixed micellar systems are explained in terms of the relative contributions to ΔmicH by alkyl chain interactions, hydrophobic effects, and electrostatic contributions.

The effects of n-butanol on oxidative stress and apoptosis in zebra fish (Danio rerio) larvae

In recent years, n-butanol has growing use in many areas, including the food industry. In this study, acute toxic effects of n-butanol to zebrafish (Danio rerio) larvae by applying different concentrations (10, 50, 250, 500, 750, 1000 and 1250 mg/L) to embryos were evaluated. For this purpose the data of oxidative stress, antioxidant - acetyl cholinesterase enzyme activities, malondialdehyde level and apoptosis were taken into consideration.At the end of the 96 h, antioxidant (Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx)) and acetylcholinesterase (AChE) enzyme activities were decreased, however lipid peroxidation level, apoptotic cells, and reactive oxygen species increased (p < .05).As a result, it has been observed that high concentrations of n-butanol with its amphiphilic structure causes quite intense toxic effects in zebrafish embryos.

Effect of n-butanol/diesel blends on performance, emission, noise and vibration characteristics of a diesel engine generator

Simple diesel engine generators in general are noisy and pollute air. It is urgently needed to find alternative fuels applicable for new as well as old engines without structural modifications and along with keeping the environment clean. Diesel-alcohol blends could be such alternatives fuels. For that purpose, in this study tests were carried out using diesel fuel first then, were carried out using three of n-butanol/diesel blends on volume bases with n-butanol concentrations of 5, 10 and 15%, identified as nBu5, nBu10 and nBu15. The engine under study is a single cylinder, four stroke, air cooled diesel engine generator and the tests have been carried out at a fixed 3000 rpm and five different load conditions without any hardware modifications. Total noise, engine block vibration, NOx, HC, CO, BSFC, BTE and EGT have been observed of diesel and n-butanol/diesel blends. The following conclusions can be drawn with nbutanol/ diesel fuel blends against diesel fuel; (i) According to engine performance test results; a little higher specific fuel consumption was observed with corresponding slight increase of brake thermal efficiency and little lower exhaust gas temperatures. (ii) According to engine emission test results; the NOx was slightly reduced, this reduction being higher the higher the percentage of butanol in the blend. The CO emissions were reduced, on the contrary, HC emissions were increased, this increase being higher the higher the percentage of butanol in the blend. According to engine vibration and noise test results; Noise and vibration characteristics are somewhat better especially at lesser loads.

Effects of acetic acid addition methods on butyl acetate enzymatic synthesis

Butyl acetate is a versatile chemical due to its excellent solvency for polymers, resins, and oils. In this work, the butyl acetate synthesis was studied by the esterification of n-butanol with acetic acid using the commercial immobilized lipase Novozym® 435. The acetic acid and n-butanol concentrations have to be limited in the enzymatic synthesis of this ester due to the deleterious effects caused by these reagents on the enzyme. Three methods of acetic acid addition (single, stepwise and continuous addition) were investigated to minimize the acid concentration. A significant drop on acid conversion was observed in the presence of a higher concentration of the reagents when single or stepwise acid addition was used. However, a solvent-free system using a continuous addition of acetic acid favored butyl acetate synthesis, reaching a conversion of 84% at 60 °C, employing 5 wt% of enzyme and n-butanol/acetic acid final molar ratio equal to 1/1.

A Pseudomonas putida efflux pump acts on short-chain alcohols

BackgroundThe microbial production of biofuels is complicated by a tradeoff between yield and toxicity of many fuels. Efflux pumps enable bacteria to tolerate toxic substances by their removal from the cells while bypassing the periplasm. Their use for the microbial production of biofuels can help to improve cell survival, product recovery, and productivity. However, no native efflux pump is known to act on the class of short-chain alcohols, important next-generation biofuels, and it was considered unlikely that such an efflux pump exists.ResultsWe report that controlled expression of the RND-type efflux pump TtgABC from Pseudomonas putida DOT-T1E strongly improved cell survival in highly toxic levels of the next-generation biofuels n-butanol, isobutanol, isoprenol, and isopentanol. GC-FID measurements indicated active efflux of n-butanol when the pump is expressed. Conversely, pump expression did not lead to faster growth in media supplemented with low concentrations of n-butanol and isopentanol.ConclusionsTtgABC is the first native efflux pump shown to act on multiple short-chain alcohols. Its controlled expression can be used to improve cell survival and increase production of biofuels as an orthogonal approach to metabolic engineering. Together with the increased interest in P. putida for metabolic engineering due to its flexible metabolism, high native tolerance to toxic substances, and various applications of engineering its metabolism, our findings endorse the strain as an excellent biocatalyst for the high-yield production of next-generation biofuels.

ACETONE-CHLOROFORM-n-BUTANOL MIXTURE SEPARATION BY THE EXTRACTIVE DISTILLATION IN SCHEMES OF TWO-OUTLET COLUMNS

Extractive distillation of acetone-chloroform-n-butanol mixture with dimethylformamide in two-outlet column schemes is considered. Optimal parameters according to the total energy consumption criterion in the column boilers of the three extractive distillation schemes for this mixture separation are determined. Calculations were carried out in a design-verification version at 1000 kg/hr of the initial mixture with the concentrations of acetone, chloroform and n-butanol 71.3, 14.7 and 14.0% wt., respectively. Dimethylformamide concentration in the entrainer flow was set to 99.99 wt%. The main component concentration in the product stream was 99.9 wt% for chloroform and 99.5 wt%. for acetone and n-butanol. The parameters to be optimized were: the number of plates in the columns, the temperature and flow rate of dimethylformamide, reflux ratios, distillate flow rates and the position of the feed plates in the columns. The optimum location of the entrainer feed plate was found additionally in the extractive distillation column. Separation product concentrations served as the constraints of the optimization. The optimization was carried out in Aspen Plus with the use of a combination of Sensitivity Analysis and sequential quadratic programming (SQP). It is established that scheme P5 has the lowest energy consumption. In the first column of this scheme, n-butanol is separated, and then the azeotrope-forming components (acetone and chloroform) are separated by the extractive distillation subsystem. Energy consumptions for two other schemes (P1 and P2), in which dimethylformamide is used in the first column of the sequence, are significantly higher than for scheme P5 - by 69.1% and by 49.3%, respectively. The data obtained will be used: to synthesize and optimize the extractive distillation schemes including the subsystems with coupled thermal and material flows to separate the acetone-chloroform-n-butanol mixture; to estimate the energy efficiency of those schemes and to obtain the criterion for estimating the energy efficiency of systems with coupled thermal and material flows in the extractive distillation of multicomponent mixtures.

PUPAL EMERGENCE INHIBITION ACTIVITY OF ACALYPHA INDICA LEAF EXTRACT AGAINST DENGUE VECTOR, AEDES ALBOPICTUS MOSQUITO

Objective: To investigate the larvicidal activities of six varying extracts of Acalypha indica (A. indica) leaves from family Euphorbiaceae against the dengue mosquito vector, Aedesalbopictus (Ae. albopictus) in laboratory.Methods: Leaves from the study plants were separated, air dried in room temperature, grounded and extracted with different solvents (petroleum ether, chloroform, ethyl acetate, n-butanol, ethanol and aqueous) by solvent apparatus and aqueous extract by maceration method. The extra solvents were evaporated to obtain crude extracts by using rotary evaporator. The crude extracts of six different solvents were dissolved in dimethyl sulphoxide (DMSO) to prepare test dosages of 1000, 2000, 3000, 4000 and 5000 ppm. Third instar larvae of Ae. albopictus were exposed to 1000, 2000, 3000, 4000 and 5000 ppm concentrations of petroleum ether, chloroform, ethyl acetate, n-butanol, ethanol and aqueous extracts of A. indica and compared with control to determine the larvicidal effects. Larval bioassays were carriedout according to World Health Organisation (WHO) procedures. The rate of larval mortality was recorded after 24h and 48 h of time exposure. Three duplicate trials were made for each tested dosage. IC50 and IC90 values were calculated by using probit analysis.Results: Based on probit analysis result the 24h and 48h LC50 and LC90 of petroleum ether extract of A. indica against Ae. albopictus was found to be 2805.43 ppm and 2376.11 ppm, 3825.14 ppm and 3327.8 ppm, respectively. An LC50 and LC90 value of chloroform extracts of A. indicaa gainst third instar larvae was found to be 2276.5 ppm and 4015.8 ppm (24h), 2213.36 ppm and 3430.43 ppm (48h), respectively. An LC50 value of 4472.17 ppm and 2469.61 ppm, and LC90 value of 4215.84 ppm was obtained on ethylacetate extract treatment against Ae. albopictus for 24h and 48h exposure, respectively. The 24h and 48 h LC50 and LC90 values of n-butanol extracts of A. indica was found to be 2777.88 ppm and 3628.19 ppm, 2225.61 ppm and 2518.86 ppm, respectively. In the present study, the larvicidal bioassays demonstrated that the n-butanolextract was most effective with 100% mortality against larvae of Ae. albopictus at 3000, 4000 and 5000 ppm compared to other extracts. All other extracts (petroleum ether, chloroform and ethyl acetate) of A. indica at high concentration (4000 ppm and 5000 ppm) manifested a significant (P&lt;0.01 and 0.05) knock down effect of 100% moratality after 24h and 48h exposure. While the third instar lavae of Ae. albopictus were found to be most susceptabile and produced no mortality to ethanol and aqueous extract at varying parts per million. Conclusion: A. indica leaf extract was tested for the first time against dengue vector Ae. albopictus and the results revealed that A. indica can be used to control dengue vector. Further this extract needs to be evaluated under field conditions for proper exploitation of Ae. albopictus mosquito larvae. Thus, the present study provided a first report on A. indica as a prompting mosquito larvicidal activity and can be considered for further investiagtions such as formulation of bioinsecticides to control Ae. albopictus populations

Effect of Biofuels on Biodegradation of Benzene and Toluene at Gasoline Spill Sites.

The risk that benzene and toluene from spills of gasoline will impact drinking water wells is largely controlled by the natural anaerobic biodegradation of benzene and toluene. Benzene and toluene, as well as ethanol and other biofuels, are degraded under anaerobic conditions to the same pool of degradation products. Biodegradation of biofuels may produce concentrations of degradation products that make the thermodynamics for degradation of benzene and toluene infeasible under methanogenic conditions and produce larger plumes of benzene and toluene. This study evaluated the concentrations of fuel alcohols that are necessary to inhibit the anaerobic degradation of benzene and toluene under methanogenic conditions. At two ethanol spill sites, concentrations of ethanol greater ≥42 mg/L inhibited the anaerobic degradation of toluene. The pH and concentrations of acetate, dissolved inorganic carbon, and molecular hydrogen were used to calculate the Gibbs free energy for the biodegradation of toluene. In general, the anaerobic biodegradation of toluene was not thermodynamically feasible in water with ≥42 mg/L ethanol. In a microcosm study, when the concentrations of ethanol were ≥14 mg/L or the concentrations of n-butanol were ≥16 mg/L, the biodegradation of the alcohols consistently produced concentrations of hydrogen, dissolved inorganic carbon, and acetate that would preclude natural anaerobic biodegradation of benzene and toluene by syntrophic organisms. In contrast, iso-butanol and n-propanol only occasionally produced conditions that would preclude the biodegradation of benzene and toluene.

Growth of Pseudomonas taiwanensis VLB120∆C biofilms in the presence of n-butanol.

SummaryBiocatalytic processes often encounter problems due to toxic reactants and products, which reduce biocatalyst viability. Thus, robust organisms capable of tolerating or adapting towards such compounds are of high importance. This study systematically investigated the physiological response of Pseudomonas taiwanensis VLB120∆C biofilms when exposed to n‐butanol, one of the potential next generation biofuels as well as a toxic substance using microscopic and biochemical methods. Initially P. taiwanensis VLB120∆C biofilms did not show any observable growth in the presence of 3% butanol. Prolonged cultivation of 10 days led to biofilm adaptation, glucose and oxygen uptake doubled and consequently it was possible to quantify biomass. Complementing the medium with yeast extract and presumably reducing the metabolic burden caused by butanol exposure further increased the biomass yield. In course of cultivation cells reduced their size in the presence of n‐butanol which results in an enlarged surface‐to‐volume ratio and thus increased nutrient uptake. Finally, biofilm enhanced its extracellular polymeric substances (EPS) production when exposed to n‐butanol. The predominant response of these biofilms under n‐butanol stress are higher energy demand, increased biomass yield upon medium complements, larger surface‐to‐volume ratio and enhanced EPS production. Although we observed a distinct increase in biomass in the presence of 3% butanol it was not possible to cultivate P. taiwanensis VLB120∆C biofilms at higher n‐butanol concentrations. Thereby this study shows that biofilms are not per se tolerant against solvents, and need to adapt to toxic n‐butanol concentrations.

Characterization of the effects of n-butanol on the cell envelope of E. coli.

Biofuel alcohols have severe consequences on the microbial hosts used in their biosynthesis, which limits the productivity of the bioconversion. The cell envelope is one of the most strongly affected structures, in particular, as the external concentration of biofuels rises during biosynthesis. Damage to the cell envelope can have severe consequences, such as impairment of transport into and out of the cell; however, the nature of butanol-induced envelope damage has not been well characterized. In the present study, the effects of n-butanol on the cell envelope of Escherichia coli were investigated. Using enzyme and fluorescence-based assays, we observed that 1% v/v n-butanol resulted in the release of lipopolysaccharides from the outer membrane of E. coli and caused 'leakiness' in both outer and inner membranes. Higher concentrations of n-butanol, within the range of 2-10% (v/v), resulted in inner membrane protrusion through the peptidoglycan observed by characteristic blebs. The findings suggest that strategies for rational engineering of butanol-tolerant bacterial strains should take into account all components of the cell envelope.