Biocidal Properties of Anti-Icing Additives for Aircraft Fuels

The biocidal and biostatic activities of seven glycol monoalkyl ether compounds were evaluated as part of an effort to find an improved anti-icing additive for jet aircraft fuel. Typical fuel contaminants, Cladosporium resinae, Gliomastix sp., Candida sp., Pseudomonas aeruginosa, and a mixed culture containing sulfate-reducing bacteria were used as assay organisms. Studies were carried out over 3 to 4 months in two-phase systems containing jet fuel and aqueous media. Diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, and 2-methoxyethanol were generally biocidal in aqueous concentrations of 10 to 17% for all organisms except Gliomastix, which required 25% or more. 2-Ethoxyethanol, 2-propoxyethanol, and 2-butoxyethanol were biocidal at progressively lower concentrations down to 1 to 2% for 2-butoxyethanol. The enhanced antimicrobial activity of these three compounds was attributed to cytoplasmic membrane damage because of the correlation between surface tension measurements and lytic activity with P. aeruginosa cells. The mechanism of action of the less active compounds appeared to be due to osmotic (dehydrating) effects. When all requirements are taken into account, diethylene glycol monomethyl ether appears to be the most promising replacement for the currently used additive, 2-methoxyethanol.     

Toxic effects of some alcohol and ethylene glycol derivatives on Cladosporium resinae.

Eleven commercially available alcohol and ethylene glycol derivatives were tested for their toxicity toward a problem organism in jet fuel, Cladosporium resinae. In the presence of glucose, 20% (vol/vol) ethylene glycol monomethyl ether prevented spore germination and mycelial growth, and 10% (vol/vol) 2-ethoxybutanol, 10% 2-isopropoxyethanol, 10% 3-methoxybutanol, 5% 2-butyloxyethanol, 5% ethylene glycol dibutyl ether, and 5% diethylene glycol monobutyl ether were found to have similar effects. In a biphasic kerosene-water system, 3-methoxybutanol, 2-butyloxyethanol, and diethylene glycol monobutyl ether were again found to be more toxic than ethylene glycol monomethyl ether. Considerable potassium efflux, protein leakage, and inhibition of endogenous respiration were observed in the presence of the more toxic compounds. 2-Butyloxyethanol also caused loss of sterols from cells.     

Effect of the fuel system icing inhibitor diethylene glycol monomethyl ether on the biodegradation of jet fuel in soil

Microbial degradation of jet fuel leads to the accumulation of sludge in fuel distribution systems and storage tanks. To prevent this phenomenon, the biocidal anti-icing inhibitor diethylene glycol monomethyl ether (DiEGME) is routinely added to the fuel. The fate of DiEGME in soil and its consequent effect on the biodegradation of jet fuel by indigenous soil microflora have not been investigated. The aim of this work was to study the kinetics of biodegradation of jet fuel in dark rendzina soil, as affected by the presence of DiEGME. Our data show that the degradability in soil of jet fuel amended with DiEGME was tenfold higher than that of non-amended fuel. Consequently, there was an increase in the jet-fuel-utilizing soil microbial populations during the 100 days of incubation of soil samples amended with jet fuel containing DiEGME. Gas chromatograms of distilled fractions of jet fuel extracted from the soil demonstrated that most of the light fractions' extracts could not be detected at the end of the 100-day incubation. The relative concentration of aromatic compounds in the soil contaminated with DiEGME-amended jet fuel increased during incubation, demonstrating the lower biodegradation rate of these components compared with other fuel components. DiEGME was partially degraded by the general microbial population of the soil. Maximal DiEGME degradation was obtained with specific jet-fuel-utilizing microbial strains – Pseudomonas aeruginosa and Cladosporium resinae – that were added to a carbon-free mineral medium. The degradation rate of DiEGME by specific strains or by soil mixed populations bore an inverse relationship to the DiEGME concentration. The finding that DiEGME can be degraded by indigenous soil microorganisms may have facilitated its utilization also by jet-fuel-degrading microorganisms.     

Corrosion of aluminum alloy 2024 by microorganisms isolated from aircraft fuel tanks

Microorganisms frequently contaminate jet fuel and cause corrosion of fuel tank metals. In the past, jet fuel contaminants included a diverse group of bacteria and fungi. The most common contaminant was the fungus Hormoconis resinae. However, the jet fuel community has been altered by changes in the composition of the fuel and is now dominated by bacterial contaminants. The purpose of this research was to determine the composition of the microbial community found in fuel tanks containing jet propellant-8 (JP-8) and to determine the potential of this community to cause corrosion of aluminum alloy 2024 (AA2024). Isolates cultured from fuel tanks containing JP-8 were closely related to the genus Bacillus and the fungi Aureobasidium and Penicillium. Biocidal activity of the fuel system icing inhibitor diethylene glycol monomethyl ether is the most likely cause of the prevalence of endospore forming bacteria. Electrochemical impedance spectroscopy and metallographic analysis of AA2024 exposed to the fuel tank environment indicated that the isolates caused corrosion of AA2024. Despite the limited taxonomic diversity of microorganisms recovered from jet fuel, the community has the potential to corrode fuel tanks.     

Corrosion of aluminum alloy 2024 by microorganisms isolated from aircraft fuel tanks

Abstract

Microorganisms frequently contaminate jet fuel and cause corrosion of fuel tank metals. In the past, jet fuel contaminants included a diverse group of bacteria and fungi. The most common contaminant was the fungus Hormoconis resinae. However, the jet fuel community has been altered by changes in the composition of the fuel and is now dominated by bacterial contaminants. The purpose of this research was to determine the composition of the microbial community found in fuel tanks containing jet propellant-8 (JP-8) and to determine the potential of this community to cause corrosion of aluminum alloy 2024 (AA2024). Isolates cultured from fuel tanks containing JP-8 were closely related to the genus Bacillus and the fungi Aureobasidium and Penicillium. Biocidal activity of the fuel system icing inhibitor diethylene glycol monomethyl ether is the most likely cause of the prevalence of endospore forming bacteria. Electrochemical impedance spectroscopy and metallographic analysis of AA2024 exposed to the fuel tank environment indicated that the isolates caused corrosion of AA2024. Despite the limited taxonomic diversity of microorganisms recovered from jet fuel, the community has the potential to corrode fuel tanks.     

Effects of polyurethane foams on microbial growth in fuel-water systems

Four, open-cell, ester-base polyurethane foams were examined for their effect on growth of fuel-utilizing organisms in jet fuel-water systems. Three foams contained a potential biocide, tetraethylthiuram E (0.66%), sodium omadine (0.07%), or zinc omadine (0.07%), all w/v. These were compared with a control foam which did not contain an additive. Each foam was examined in fuel-water systems containing JP-4 fuel, JP-4 fuel plus 0.1% anti-icing additive (AIA), or JP-5 fuel. Pure cultures of a fuel-grown bacterium, Pseudomonas aeruginosa, and of a fuel-grown fungus, Hormodendrum (Cladosporium) sp., served as test organisms. In control cultures without foam and in cultures containing control foam, P. aeruginosa achieved maximum stationary-phase populations of approximately 10⁸ viable cells per ml, and Hormodendrum sp. produced an extensive mycelial mat. In the three fuel systems examined, tetraethylthiuram E- and sodium omadine-containing foams had little effect on growth of the bacterium; foam with zinc omadine decreased the rate of bacterial growth but had little effect on total populations. Tetraethylthiuram E decreased the rate of fungal growth and showed its greatest effect in JP-4 plus AIA. Foam with sodium omadine or zinc omadine markedly decreased fungal growth in all three fuel systems. The data suggest that either sodium omadine or zinc omadine in polyurethane foam may be a useful antifungal agent; and that tetraethylthiuram E and AIA could exert a synergistic effect, particularly at AIA concentrations which have been reported to occur in some field situations.     

Use of glycol ethers for selective release of periplasmic proteins from Gram-negative bacteria

Genetic modification of Gram-negative bacteria to express a desired protein within the cell's periplasmic space, located between the inner cytoplasmic membrane and the outer cell wall, can offer an attractive strategy for commercial production of therapeutic proteins and industrial enzymes. In certain applications, the product expression rate is high, and the ability to isolate the product from the cell mass is greatly enhanced because of the product's compartmentalized location within the cell. Protein release methods that increase the permeability of the outer cell wall for primary recovery, but avoid rupturing the inner cell membrane, reduce contamination of the recovered product with other host cell components and simplify final purification. This article reports representative data for a new release method employing glycol ether solvents. The example involves the use of 2-butoxyethanol (commonly called ethylene glycol n-butyl ether or EB) for selective release of a proprietary biopharmaceutical protein produced in the periplasmic space of Pseudomonas fluorescens. In this example, glycol ether treatment yielded approximately 65% primary recovery with approximately 80% purity on a protein-only basis. Compared with other methods including heat treatment, osmotic shock, and the use of surfactants, the glycol ether treatment yielded significantly reduced concentrations of other host cell proteins, lipopolysaccharide endotoxin, and DNA in the recovered protein solution. The use of glycol ethers also allowed exploitation of temperature-change-induced phase splitting behavior to concentrate the desired product. Heating the aqueous EB extract solution to 55 degrees C formed two liquid phases: a glycol ether-rich phase and an aqueous product phase containing the great majority of the product protein. This phase-splitting step yielded an approximate 10-fold reduction in the volume of the initial product solution and a corresponding increase in the product's concentration.     

Oxidation of lignans and lignin model compounds by laccase in aqueous solvent systems

The stability and activity of the low redox potential Melanocarpus albomyces laccase (MaL) in various aqueous organic (acetone, ethanol, propylene glycol, diethylene glycol monomethyl ether) solvent systems was studied spectrophotometrically using 2,6-dimethoxyphenol (2,6-DMP) as substrate. In addition, reactivity of the enzyme with two lignans; matairesinol (MR) and 7-hydroxymatairesinol (HMR), was examined by oxygen consumption measurements in the most potential aqueous organic solvent systems. Polymerization of the lignans by MaL was verified by matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and size exclusion chromatography (SEC). Polymerization of the higher molecular weight lignin model compound, dehydrogenation polymers (DHPs), was studied by SEC. The solubilities of industrial softwood and hardwood kraft lignins were evaluated as parameters for investigation of enzymatic modification in aqueous organic solvent systems. The functioning of MaL in different aqueous organic media was excellent. Propylene glycol and diethylene glycol monomethyl ether were better solvents than ethanol or acetone in enzymatic oxidations. Even though they were the best solvents for enzyme oxidation, ethanol and propylene glycol were selected for further tests because of their different physicochemical properties. The results obtained in this study for the use of laccase-catalysed reactions in organic solvents to improve the efficiency of lignin oxidation may be exploited in several applications and areas in which the solubility of the reactants or products is a limiting factor.     

Growth and survival of fuel isolates in hydrocarbon-fuel emulsions

Two fuel utilizers, a strain of Pseudomonas aeruginosa and a Hormodendrum sp., and two fuel isolates which did not use fuel, Staphylococcus and Bacillus spp., were tested for ability to survive and grow in systems containing emulsified or nonemulsified forms of JP-4 jet fuel. Neither emulsion (Alamac no. 1 or Alamac no. 2) supported microbial growth without a water phase. Growth of P. aeruginosa in liquid systems containing either emulsion was not significantly different from growth in liquid systems with nonemulsified fuel. The Hormodendrum sp. grew well in a liquid medium containing nonemulsified JP-4, but when either of the emulsions served as carbon source no growth was observed. However, good growth was noted on spread plates with either emulsion. Viable cells of Bacillus sp. did not increase over a 4-day period, and Staphylococcus sp. did not survive in liquid systems containing JP-4 or emulsions.     

Mutagenicity and cytotoxicity of 2-butoxyethanol and its metabolite, 2-butoxyacetaldehyde,in Chinese hamster ovary (CHO-AS52) cells

2-Methoxyethanol (2-ME) is being substituted by 2-butoxyethanol (2-BE) as a solvent for the preparation of industrial and consumer products. Since we have shown that a metabolite of 2-methoxyethanol, methoxyacetaldehyde (MALD), is mutagenic in a subline of Chinese hamster ovary cells (CHO-AS52), we have conducted a similar study using 2-BE and its metabolite, butoxyacetaldehyde (BALD). The results indicate that 2-BE and BALD are not mutagenic to CHO-AS52 cells. However, 2-BE is more cytotoxic than 2-ME. In comparison of our study with others on glycol ethers, the data indicate that, for glycol ethers, cytotoxicity increased with chain length of the alkyl groups. For their metabolites, mutagenicity increases with reduced chain length. Therefore, we suggest that safer solvents should be developed for use in preparation of products.     

Direct counting of tissues containing radioactive cholesterol by a two-phase liquid scintillation method

A rapid and simple method for counting radioactivity in tissue samples containing [³H]- or [¹⁴C]-cholesterol is described.Up to 500 μl of the specimen to be counted (plasma, tissue homogenate) is measured into a counting vial. The lipids of the tissue are extracted into 15 ml of a toluene-based scintillation mixture containing 37.5% ethylene glycol monomethyl ether that is added to the same vial. With the addition of 1 ml water, two phases form: the upper toluene phase containing all cholesterol together with the scintillating phosphor and the lower water phase containing most of the quenching material. Bleaching to reduce color quenching is not necessary. Chemiluminescence is negligible. The counting efficiencies are appreciably higher than those obtained in aqueous one-phase scintillation systems but lower than those obtained with pure standards in one-phase pure toluene scintillation systems.     

Conformational studies on poly-L-tryptophan: circular dichroism and x-ray diffraction studies

Circular dichroism (CD) measurements were carried out on various copolymers of L -tryptophan and γ-ethyl L -glutamate in ethylene glycol monomethyl ether as the solvent. On increasing the L -tryptophan content of the copolymers a gradual change in the CD spectra was observed. The typical spectrum of the right-handedα-helix becomes more and more evident as the L -tryptophan content decreases. On the basis of these results we assumed that no conformational transition occurs on proceeding from pure poly (γ-ethyl L -glutamate) to pure poly-L -tryptophan in ethylene glycol monomethyl ether: therefore the conformation of poly-L -tryptophan should be that of a right-handed α-helix. Moreover we observed that the change in the CD spectra of the copolymers is gradual but not linear on increasing the tryptophan content. The deviations from linearity were attributed to interactions among side-chain chromophores whose contributions to the optical activity are not simply additive. An x-ray analysis carried out on oriented films of poly-L -tryptophan casted from solutions of the polymer in dimethylformamide shows conclusively that the solid-state conformation of the polymer is that, of an α-helix.     

Comparative responses of Pseudomonas stutzeri and Pseudomonas aeruginosa to antibacterial agents

The sensitivity of six strains of Pseudomonas stutzeri (NCIMB 568, 10783, 11358, 11359, JM 302, JM 375) to cationic antiseptics, mercury compounds, the parabens, phenolics, EDTA and various antibiotics was compared with Pseudomonas aeruginosa NCIMB 8626. All Ps. stutzeri strains were highly sensitive to chlorhexidine diacetate, organomercurials and triclosan, but rather less so to quarternary ammonium compounds (QACs). They were also sensitive to other biocidal agents and more sensitive to many antibiotics than the strain of Ps. aeruginosa. There was little correlation between uptake of chlorhexidine diacetate or cetylpyridinium chloride by dense suspensions of organisms, leakage of intracellular constituents and loss of cell viability.     

Preparation of cholesteric (hydroxypropyl)cellulose/polymer networks and ion-mediated control of their optical properties

(Hydroxypropyl)cellulose (HPC)/vinyl polymer networks were synthesized in film form from liquid-crystalline solutions of HPC in a mixed solvent of methacrylate monomer/methanol/water (2:1:2 in weight) containing cross-linking agents, via photopolymerization of the methacrylate monomer. Di(ethylene glycol) monomethyl ether methacrylate (DEGMEM) or 2-hydroxypropyl methacrylate (HPMA) was used as the polymerizing monomer, and tetra(ethylene glycol) diacrylate and glutaraldehyde were the cross-linkers for the monomers and HPC, respectively. The polymer composite films, HPC/PDEGMEM and HPC/PHPMA, prepared at ca. 60-70 wt % concentrations of HPC in the starting solutions, were iridescently colored due to the selective light reflection, originating from the cholesteric helical arrangement carried over successively into the network system. When the cholesteric films were immersed and swollen in water containing an inorganic neutral salt, their coloration and optical turbidity varied according to a strength of 'chaotropicity' of the impregnant ions. This ionic effect may be interpreted as essentially identical with that found formerly in the coexistent salt-sort dependence of the cholesteric pitch and lower critical solution temperature for HPC aqueous solutions. It is also demonstrated that visual appearance of the swollen networks can be changed by application of an electric potential of practical magnitude between both edges of the samples of rectangular shape.     

Bacterial degradation of glycol ethers

Assimilation of ethyleneglycol (EG) ethers by polyethyleneglycol-utilizing bacteria was examined. Ethyleneglycol ether-utilizing bacteria were also isolated from soil and activated sludge samples by enrichment-culture techniques. Three strains (4-5-3, EC 1-2-1 and MC 2-2-1) were selected and characterized as Pseudomonas sp. 4-5-3, Xanthobacter autotrophicus, and an unidentified gram-negative, non-spore-forming rod respectively. Their growth characteristics were examined: Pseudomonas sp. 4-5-3 assimilated EG (diethyleneglycol, DEG) monomethyl, monoethyl and monobutyl ethers, DEG, propanol and butanol. X. autotrophicus EC 1-2-1 grew well on EG monoethyl and monobutyl ethers, EG and primary alcohols (C₁-C₄), and slightly on EG monomethyl ether. The strain MC 2-2-1 grew on EG monomethyl ether, EG, primary alcohols (C₁-C₄), and 1,2-propyleneglycol (PG). The mixed culture of Pseudomonas sp. 4-5-3 and X. autotrophicus EC 1-2-1 showed better growth and improved degradation than respective single cultures towards EG monomethyl, monoethyl or monobutyl ethers. Intact cells of Pseudomonas sp. 4-5-3 degraded various kinds of monoalkyl ethers, which cannot be assimilated by the strain. Metabolic products were characterized from reaction supernatants of intact cells of Pseudomonas sp. 4-5-3 with EG or DEG monoethyl ethers: they were analyzed by thin-layer chromatography and GC-MS and found to be ethoxyacetic acid and ethoxyglycoxyacetic acid. Also, PG monoalkyl ethers (C₁-C₄), dipropyleneglycol monoethyl and monomethyl ethers and tripropyleneglycol monomethyl ether were assimilated by polypropyleneglycol-utilizing Corynebacterium sp. 7.     

Synthesis and characterization of water-soluble two-photon excited blue fluorescent chromophores for bioimaging.

We report here the synthesis and characterization of a new type of non-ionic blue fluorescent water-soluble chromophores specifically designed for two-photon absorption microscopy. The water solubility is induced by introduction of short oligo(ethylene glycol) monomethyl ether moieties. This work has led to low molecular weight dyes with efficient two-photon absorption cross sections and high fluorescence quantum yield in organic solvents as well as in aqueous solutions.     

Substituted Diazenes: Effect on the Growth of Enterobacteria and Possible Use as Selective Agents for Isolation of Pseudomonads

Incorporation of various diazenes into Trypticase soy media appeared selectively to permit the growth of pseudomonads while inhibiting the growth of a variety of enterobacteria. One of these diazenes, diamide (diazenedicarboxylic acid bisdimethylamide), was shown to be bactericidal for pure cultures of Escherichia coli, Proteus sp., and Salmonella enteritidis and to cause a 1- to 2-hr delay in the growth of Pseudomonas aeruginosa. When mixtures of these four organisms were inoculated into Trypticase soy broth or Trypticase soy agar (TSA) containing diamide, P. aeruginosa grew in overnight cultures. TSA containing diamide was also used successfully to isolate pseudomonads from soil, clinical urine specimens, fish, ground beef, ground pork, and ground veal.     

Evaluation of encapsulation stress and the effect of additives on viability and photosynthetic activity of <Emphasis Type="Italic">Synechocystis</Emphasis> sp. PCC 6803 encapsulated in silica gel

Stresses imposed on the cyanobacterium Synechocystis sp. PCC 6803 by various compounds present during silica sol–gel encapsulation, including salt, ethanol (EtOH), polyethylene glycol (PEG), glycerol, and glycine betaine, were investigated. Viability of encapsulated cells and photosynthetic activity of cells stressed by immediate (2 min) and 24-h exposure to the five stress-inducing compounds were monitored by pulse amplitude modulated fluorometry. Cells of Synechocystis sp. PCC 6803 readily survive encapsulation in both alkoxide-derived gels and gels from aqueous precursors and can remain active at least 8 weeks with slight degradation in PSII efficiency. Post-encapsulation survival was improved in gels containing no additive when compared with gels containing PEG or glycerol. Glycerol was shown to have a detrimental effect on Synechocystis sp. PCC 6803, reducing ϕPSII and F _v′/F _m′ by as much as 75%, possibly a result of disrupting excitation transfer between the phycobilisomes and photosystems. PEG was similarly deleterious, dramatically reducing the ability to carry out a state transition and adequately manage excitation energy distribution. EtOH stress also hindered state transitions, although less severely than PEG, and the cells were able to recover nearly all photosynthetic efficiency within 24 h after an initial drop. Betaine did not interfere with state transitions but did reduce quantum yield and photochemical quenching. Finally, Synechocystis sp. PCC 6803 was shown to recover from salt stress.     

Biodegradation of methyl tertiary butyl ether (MTBE) by a bacterial enrichment consortia and its monoculture isolates

Methyl tertiary butyl ether (MTBE), an important gasoline additive, is a recalcitrant compound posing serious environmental health problems. In this study, MTBE-degrading bacteria were enriched from five environmental samples. Enrichments from Stewart Lake sediments and an MTBE contaminated soil displayed the highest rate of MTBE removal; 29.6 and 27.8% respectively, in 28 days. A total of 12 bacterial monocultures isolated from enrichment cultures were screened for MTBE degradation in liquid cultures. In a nutrient-limited medium containing MTBE as the sole source of carbon and energy, the highest rate of MTBE elimination was achieved with IsoSL1, which degraded 30.6 and 50.2% in 14 and 28 days, respectively. In a nutrient-rich medium containing ethanol and yeast extract, the bacterium (Iso2A) substantially removed MTBE (20.3 and 28.1% removal in 14 and 28 days, respectively). Based upon analysis of the 16s rRNA gene sequence and data base comparison, IsoSL1 and Iso2A were identified as a Streptomyces sp. and Sphingomonas sp., respectively. The Streptomyces sp. is a new genera of bacteria degrading MTBE and could be useful for MTBE bioremediation.     

A note on antibiotic resistance in the bacterial flora of raw sewage and sewage-polluted River Tigris in Mosul, Iraq

Polluted water samples collected from the River Tigris in the vicinity of a raw sewage outfall were examined for the incidence of antibiotic resistance among coli-form bacteria on three occasions during 1983. Eighty percent or more of the coli-form bacteria were resistant to one or more antibiotics. At the same time, raw sewage samples were examined for the incidence of antibiotic-resistant bacteria, and Escherchia coli, Pseudomonas spp. and Staphylococcus spp. were selected for sensitivity testing. Collectively, more than 90% of the 480 strains of the three organisms were resistant to one or more antibiotics. The minimal inhibitory concentration (MIC) of ampicillin for twenty-nine strains including coliforms, E. coli, Klebsiella sp., Serratia sp., Ps. aeruginosa, Pseudomonas sp., Micrococcus sp., Staph. aureus, Streptococcus faecalis and Bacillus sp. from raw sewage and polluted River Tigris water was determined and that for Ps. aeruginosa was 250 μg/ml. The high incidence of antibiotic-resistant bacteria in natural waters could be related to the widespread use of antibiotics in this locality.