Effect of micellar solubilization on biodegradation rates of hydrocarbons
01 Jan 1993-Environmental Science & Technology (American Chemical Society)-Vol. 27, Iss: 1, pp 104-110
TL;DR: Except for very low hydrocarbon concentrations, the Monod model for a single substrate was able to describe reasonably well the time dependence of both cell growth and hydrocarbon consumption for experiments with n-decane.
Abstract: Batch experiments were conducted with a strain of Pseudomonas aeuroginsa and a strain of Ochrobactrum anthropi, both Gram-negative bacteria, growing on aqueous solutions containing straight-chain hydrocarbons solubilized in small micelles (204 nm) of nonionic surfactants. Measurements of optical density, a quantity proportional to bacterial cell concentration, and hydrocarbon content were made as a function of time. Since no macroscopic hydrocarbon drops were present and therefore there was no opportunity for the bacteria to attach themselves to oil-water interfaces, the results provided unambiguous confirmation that solubilization greatly enhances rates of hydrocarbon degradation in these systems compared to rates observed with bulk liquid hydrocarbon in the absence of surfactants. Solubilization of n-decane and n-tetradecane in micelles reduced the times required for cell density to double during exponential growth by a factor of {approximately}5 for one bacterial strain compared to results obtained for surfactant-free experiments. The improvement was even greater for the other strain. Except for very low hydrocarbon concentrations, the Monod model for a single substrate was able to describe reasonably well the time dependence of both cell growth and hydrocarbon consumption for experiments with n-decane. 28 refs., 4 figs.
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TL;DR: The physiological responses of microorganisms to the presence of hydrocarbons, including cell surface alterations and adaptive mechanisms for uptake and efflux of these substrates, have been characterized and used to investigate the dynamics of microbial communities in petroleum-impacted ecosystems.
Abstract: Recent advances in molecular biology have extended our understanding of the metabolic processes related to microbial transformation of petroleum hydrocarbons. The physiological responses of microorganisms to the presence of hydrocarbons, including cell surface alterations and adaptive mechanisms for uptake and efflux of these substrates, have been characterized. New molecular techniques have enhanced our ability to investigate the dynamics of microbial communities in petroleum-impacted ecosystems. By establishing conditions which maximize rates and extents of microbial growth, hydrocarbon access, and transformation, highly accelerated and bioreactor-based petroleum waste degradation processes have been implemented. Biofilters capable of removing and biodegrading volatile petroleum contaminants in air streams with short substrate-microbe contact times ( 2 S and sulfoxides from petrochemical waste streams. Microbes also have potential for use in removal of nitrogen from crude oil leading to reduced nitric oxide emissions provided that technical problems similar to those experienced in biodesulfurization can be solved. Enzymes are being exploited to produce added-value products from petroleum substrates, and bacterial biosensors are being used to analyze petroleum-contaminated environments.
1,346 citations
Cites background from "Effect of micellar solubilization o..."
...While microorganisms may contact water-solubilized hydrocarbons, decreasing solubility with increasing molecular weight is restrictive (91)....
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TL;DR: Biosurfactants are widely used for various purposes in industry, but for many years were mainly chemically synthesized as mentioned in this paper, and there are conflicting reports regarding their efficacy and the economics of both their production and application, and caution is frequently exercised with respect to their use because of possible subsequent microbial contamination of either underground oil reservoirs or products.
740 citations
TL;DR: An overview of the recent developments in the area of surfactant enhanced soil and groundwater remediation processes, focusing on micellar solubilization of organic hydrocarbons, and some laboratory and field studies on removal of organics from contaminated soil are reviewed to show the applicability of this technology.
456 citations
TL;DR: The complexity of the effect of surfactants onpollutant bioavailability is reflected by the results, which range from stimulation to inhibition of desorption and biodegradation of polluting compounds, and no general trends can be found.
Abstract: Biodegradation of hydrophobic organic compounds in polluted soil is a process involving interactions among soil particles, pollutants, water, and micro-organisms. Surface-active agents or surfactants are compounds that may affect these interactions, and the use of these compounds may be a means of overcoming the problem of limited bioavailability of hydrophobic organic pollutants in biological soil remediation. The effects of surfactants on the physiology of micro-organisms range from inhibition of growth due to surfactant toxicity to stimulation of growth caused by the use of surfactants as a co-substrate. The most important effect of surfactants on the interactions among soil and pollutant is stimulation of mass transport of the pollutant from the soil to the aqueous phase. This can be caused by three different mechanisms: emulsification of liquid pollutant, micellar solubilisation, and facilitated transport. The importance of these mechanisms with respect to the effect of surfactants on bioavailability is reviewed for hydrophobic organic pollutants present in different physical states. The complexity of the effect of surfactants on pollutant bioavailability is reflected by the results in the literature, which range from stimulation to inhibition of desorption and biodegradation of polluting compounds. No general trends can be found in these results. Therefore, more research is necessary to make the application of surfactants a standard tool in biological soil remediation.
437 citations
Cites background or methods from "Effect of micellar solubilization o..."
...More evidence for this mechanism is given by Bury & Miller (1993), who found that uptake of micellarn-decane andn-tetradecane was stimulated by a biodegradable surfactant, resulting in higher growth rates....
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...In the literature, three mechanisms for the microbial uptake of liquid hydrocarbons have been proposed (Bury & Miller 1993; Hommel 1990): (i) uptake of hydrocarbon dissolved in the aqueous phase; (ii) direct uptake of hydrocarbons from the liquid-liquid interface; (iii) uptake of…...
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...In addition to this, it is advisable to perform simple standardised laboratory experiments in which the effect of the surfactant on the mobilisation and biodegradation of the pollutant is determined, e.g., Bury and Miller 1993, Grimberg et al. 1996, and Volkering et al. 1995....
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TL;DR: Toxicity of the surfactants decreased with increasing hydrophilicity, i.e., with increasing ethoxylate chain length, and enhanced the degradation of fluorene, phenanthrene, anthracene, fluoranthene, and pyrene.
Abstract: The biodegradation of polycyclic aromatic hydrocarbons (PAH) often is limited by low water solubility and dissolution rate. Nonionic surfactants and sodium dodecyl sulfate increased the concentration of PAH in the water phase because of solubilization. The degradation of PAH was inhibited by sodium dodecyl sulfate because this surfactant was preferred as a growth substrate. Growth of mixed cultures with phenanthrene and fluoranthene solubilized by a nonionic surfactant prior to inoculation was exponential, indicating a high bioavailability of the solubilized hydrocarbons. Nonionic surfactants of the alkylethoxylate type and the alkylphenolethoxylate type with an average ethoxylate chain length of 9 to 12 monomers were toxic to a PAH-degrading Mycobacterium sp. and to several PAH-degrading mixed cultures. Toxicity of the surfactants decreased with increasing hydrophilicity, i.e., with increasing ethoxylate chain length. Nontoxic surfactants enhanced the degradation of fluorene, phenanthrene, anthracene, fluoranthene, and pyrene.
413 citations