Biodegradation of Petroleum Oil Effluents and Production of Biosurfactants: Effect of Initial Oil Concentration

Biosurfactants have been used in the petroleum oil industry for oil storage tank cleaning, for reducing the viscosity of heavy oil, thereby facilitating recovery, transportation, and pipelining. Also, they are used for microbial enhanced oil recovery either from residual oil in reservoirs or from oily wastewater. The present study is an investigation of biodegradation of petroleum oil effluents using Pseudomonas aeruginosa ATCC 9027 for producing rhamnolipid biosurfactants. The processes were performed in a mechanically agitated, fully baffled, air-sparged 10 L glass fermenter with a 5 L working volume. The effect of oil concentration (1%, 1.5%, 2%, and 2.5%) on the efficiency of oil biodegradation, rhamnolipid production, surface tension, and bacterial biomass was studied. The fermentation with 1.5% oil concentration gave the highest biodegradation for aliphatic hydrocarbons (98.85%), followed by 2% oil concentration (95% degradation), then with 2.5% oil concentration (80% degradation), and finally with 1% oil concentration (66.8% degradation). Also, the complete biodegradation of polyaromatic hydrocarbons was achieved for all tested oil concentrations. On the other hand, maximum rhamnolipid production of 2.7 g L⁻¹ as rhamnose equivalent and lower surface tension (30.2 mN m⁻¹) were achieved at 2% oil concentration.     

Improving solubilization in microemulsions with additives. Part III: Lipophilic linker optimization

Polar oil additives are able to substantially improve the solubilization in surfactant-oil-water microemulsions through the so-called lipophilic linker effect. Long-chain alcohols (above C₈) and their low ethoxylation derivatives were found to produce such an improvement. A method is proposed to evaluate the lipophilic linker performance and to compare lipophilic linker candidates in different oil-surfactant systems. The best lipophilic linker was found to have a hydrophobe chain length as an average between that of the surfactant tail and the n-alkane oil. The experimental data agree with that obtained by using a simple model based on the estimation of molecular interactions.     

Diesel Oil Degradation Potential of a Bacterium Inhabiting Petroleum Hydrocarbon Contaminated Surface Waters and Characterization of Its Emulsification Ability

Degradation of poorly water soluble hydrocarbons, like n‐alkanes and polycyclic aromatic hydrocarbons are challenged by some bacteria through emulsification of hydrocarbons by producing biosurfactants. In diesel oil bioremediation, diesel oil degrading and surfactant producing bacteria are used to eliminate these pollutants from contaminated waters. Therefore, identifying and characterizing bacteria capable of producing surfactant and degrading diesel oil are pivotal. In this study, bacteria isolated from hydrocarbon contaminated river water were screened for their potential to degrade diesel oil. Primary selection was carried out by using conventional enrichment culture technique, emulsification index measurement, gravimetric and gas chromatographic analyses of diesel oil degradation. A bacterium with 60 % emulsification index and 92 % diesel oil degradation ability in 14 days was identified as Acinetobacter haemolyticus Zn01 by 16S rRNA sequencing. A. haemolyticus Zn01 was shown to harbor both catabolic genes alkB and C23O effective in diesel oil degradation. The biosurfactant of the bacterium was also characterized in terms of surface tension, zeta potential, Fourier transform infrared spectroscopy and scanning electron microscopy. Being able to emulsify and degrade diesel oil, A. haemolyticus Zn01 seems to have high potential for the elimination of diesel oil from polluted waters.     

Biodegradation of heavy oil by fungal extracellular enzymes from Aspergillus spp. shows potential to enhance oil recovery

Microbial enhanced oil recovery makes a substantial contribution to the recovery of heavy oils; however, most methods use bacteria, with less attention paid to the potential of fungi. In this study, we investigated the efficiency of fungal extracellular enzymes in biotransformation of heavy oil fractions into light compounds. Two Aspergillus isolates (A. terreus and A. nidulans) with the ability to biodegrade heavy oil were isolated from bitumen. The extracellular enzymes from these Aspergillus isolates exhibited dehydrogenase and catechol 2,3-dioxygenase activities. The biodegradation of heavy oil was coupled with abundant production of gases, mainly CO₂ and H₂. Gas chromatography analysis revealed a redistribution of n-alkanes in heavy oil after treatment with crude enzyme extracts, which resulted in an increase in individual n-alkanes. The viscosity of heavy oil was decreased considerably by enzymatic degradation. These results demonstrate the potential of fungal extracellular enzymes from Aspergillus spp. for applications in enhanced heavy oil recovery.     

Oxidative degradation and molecular weight change of LDPE buried under bioactive soil for 32–37 years

The molecular weight reduction of low-density polyethylene (LDPE) buried under bioactive soil for 32–37 years was examined by GPC. Microscope IR spectra of the surface of the degraded sample showed the characteristic feature of biodegradation, while the inner part of the sample was almost unchanged. The number average molecular weight (M_n) of the surface was reduced to almost one-half of the inner part. Moreover, a low-molecular-weight component around a molecular weight of 10³ was recognized for degraded samples. SEM observation suggested that the formation of the low-molecular-weight components is the result of erosion due to enzymatic reaction. The results give evidence for the biodegradation of high-molecular-weight LDPE. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1643–1659, 1998     

Surface characterization of poly(ethylene terephthalate) film by inverse gas chromatography

The gas-chromatographic retention of a series of n-alkanes at effectively zero coverage was measured on a poly(ethylene terephthalate) film surface, and the free energy of adsorption per—CH₂—segment of n-alkane at zero surface coverage, Δ?, was calculated. This quantity is a direct measure of the London (nonpolar) interactions of the surface. A value of 40 mN/m for γ^1/2, the London Component of the polyester surface free energy, may be estimated from the gas-chromatographic results, in good agreement with results from contact angle measurements. The complete adsorption isotherm and spreading pressure for n-decane were also measured by finite-concentration gas chromatography. The method is restricted to polar or crystalline polymers, where the n-alkane does not penetrate the bulk of the material during the measurements.     

Influence of Oil Properties on Bed Coalescence Efficiency

Abstract

Bed coalescence efficiency of oil separation from formation water was studied on model systems involving 10 real samples of crude oil and its fractions of different characteristics. Oil components were varied and all other parameters were kept constant, and high mineralization water served as the continuous phase. All experiments were realized on a commercial WO/O4 two-stage bed coalescer. Temperature, oil content, and fluid velocity were kept constant for all samples. Model emulsion was dispersed by constant stirring during the experiment to obtain primarily droplets of 20 μm diameter. Correlations for predicting the coalescence efficiency as a function of some physical and chemical oil properties are presented. The investigated oil components ensured a wide span of viscosity, density, and interfacial tension. The influences of mean molecular weight, neutralization number, as well as the contents of n-alkenes, NSO, and aromatics on coalescence efficiency were analyzed. On the basis of the empirical dependences of coalescence efficiency on individual parameters obtained by regression analysis of the data, a general mathematical model was established.     

Effect of an emulsifying surfactant on diesel degradation by cultures exhibiting inducible cell surface hydrophobicity

BACKGROUND: Accumulation of petroleum hydrocarbons in the environment is often attributed to inherently slow degradation rates. This study was conducted to determine if diesel biodegradation by cultures exhibiting inducible cell surface hydrophobicity could be enhanced by addition of a chemical surfactant promoting emulsification. Experiments were designed to determine quantitatively the enhancement in diesel degradation caused by Triton X‐100 for two bacterial cultures, Exiguobacterium aurantiacum and Burkholderia cepacia. RESULTS: In the presence of Triton X‐100 at twice the critical micelle concentration (CMC) the extent of degradation in whole diesel in 5 days was 1.6–1.8 times that observed over 15 days with no surfactant. The enhancement in overall degradation of diesel range resolved peaks (DRRP, representing n‐alkanes and branched alkanes) was 1.76 and 1.26 times for E. aurantiacum and B. cepacia cultures respectively. Although an enhancement in decay rate was observed for all n‐alkane components, it was most significant for C19, C25 and pristane. CONCLUSION: For cultures exhibiting direct interfacial uptake, the beneficial effect of an emulsifying surfactant found here is in contrast to earlier studies reporting a detrimental effect due to detachment of cells from the oil/water interface. Surfactant addition may have significant potential in enhancing degradation of the more recalcitrant components. Copyright © 2007 Society of Chemical Industry     

Deformation behavior of polystyrene as a function of molecular weight parameters

The mechanical deformation of polystyrene as it relates to molecular weight parameters was investigated. Mechanical testing consisted of uniaxial tension and compression experiments on a variety of polystyrenes. Such quantities as modulus, proportional limit, and various yield stress measurements were determined on polystyrene samples of controlled number-average molecular weight and molecular weight distribution. A basic tool for the mechanical behavior analysis was the use of a power law equation σ = K?ⁿ to examine the initial nonlinear region of each experimentally determined stress–strain curve. Correlations between mechanical deformation and molecular weight parameters were determined using statistical linear regression analysis. It was generally found for uniaxial tension that mechanical parameters in or near the elastic region were independent of M?_n and MWD, while at larger strains correlations were found. For uniaxial compression, stress maxima and the strain where this occurred increased with increasing MWD. Otherwise, mechanical parameter changes in uniaxial compression did not occur with changing M?_n and MWD. Finally, a direct comparison of tension versus compression showed only the initial moduli to be the same. All other mechanical parameters showed significantly differing values, indicating different deformation mechanisms operating in tension verus compression. The analysis of this behavior from both a mechanics and molecular weight viewpoint provides some insight about glassy polymer deformation processes on the microscopic level.     

Mathematical model for growth process of a recombinant yeast having saccharification and fermentation activities

A mathematical model for direct alcohol fermentation from starch was proposed using an amylase‐producing recombinant yeast, Saccharomyces cerevisiae SR93. This model consisted of the reaction rate equations for glucoamylase synthesis in the recombinant yeast, starch degradation by a glucoamylase, cell growth, production of glucose, and production of ethanol. The rate of glucoamylase synthesis was expressed on the basis of the diauxic growth model that represents catabolite repression and enzyme induction. The rate of starch degradation was expressed on the basis of the enzymatic hydrolysis model representing the change of structure resulting from starch degradation. The calculated values were in satisfactory agreement with the experimental data in a batch culture of direct alcohol fermentation from starch using S cerevisiae SR93. Furthermore, the calculated values obtained by changing only one parameter concerning the synthesis rate of glucoamylase were in satisfactory agreement with the experimental data using another recombinant yeast, S cerevisiae SR96. Copyright © 2003 Society of Chemical Industry     

Surface Tension in Relation to Cohesive Energy with Particular Reference to Hydrocarbon Polymers

A known relationship between heat of vaporisation, surface tension and molar volume applicable to spherical non-polar molecules is modified to apply also to linear molecules; the treatment involves calculation of molar surface areas corresponding to the appropriate “fully-packing” molecular shapes.

A linear relationship between the ratio cohesive energy density/surface tension and the reciprocal of molar volume is predicted for members of homologous series and demonstrated, with data for the n-paraffins.     

Partial oxidation of n-hexadecane and polyethylene in supercritical water

In this study, we show the results of partial oxidation experiments of n-hexadecane (n-C₁₆) and polyethylene (PE) in supercritical water (SCW). The experiments were carried out at 673 or 693 K of reaction temperature and 5 or 30 min of reaction time using a 6 cm³ of a batch type reactor. Water density ranged from 0.1 to 0.52 g/cm³ (water pressure: 20–40 MPa). The loaded amount of oxygen was set to 0.3 of the ratio of oxygen atom to carbon atom. Some experiments were made using CO instead of oxygen for the partial oxidation of n-C₁₆ and PE to explore the effect of water gas shift reaction. In the results of partial oxidation of n-C₁₆, the yield of CO and some compounds containing oxygen atoms, such as aldehydes and ketones increased with increasing water density. Moreover, 1-alkene/ n-alkane ratio in the products decreased with increasing water density. The 1-alkene/n-alkane ratio was lower than that of pyrolysis in SCW. Also for the case of PE experiments, in dense SCW (0.42 g/cm³), the 1-alkene/n-alkane ratio in partial oxidation was lower than that in SCW pyrolysis. In the case of CO experiments for n-C₁₆ and PE, 1-alkene/n-alkane ratio was a little lower than that of pyrolysis in SCW. These results show that the yield of n-alkane, which is a hydrogenated compound, was higher through water gas shift reaction in SCW and also through partial oxidation in SCW. Therefore, these results suggest the possibility of hydrogenation of hydrocarbon through partial oxidation followed by the water gas shift reaction.     

Synthesis of copolymers of N,N-dimethyl acrylamide and methacrylate esters and their surface tensions

A systematic study was made on the preparation of N,N-dimethylacrylamide (NDMA)/ methacrylic ester statistical copolymers. The methacrylic ester comonomers used in the copolymerizations were ethyl, n-butyl, n-hexyl, n-octyl, n-dodecyl, n-hexadecyl, and n-octadecyl methacrylates. It was found that the NDMA copolymers could be prepared in three molecular weight regions: 1.0 × 10⁴, 2.0 × 10⁵, and greater than 1.0 × 10⁶ ([η] in water at 30°C of 0.1, 0.6, and greater than 1.5 dL/g, respectively). The molecular weights of the copolymers were dependent on the solvent employed in the polymerizations and on the presence of a chain transfer agent (t-dodecyl mercaptan). All copolymer compositional analyses were made by 400 MHz ¹H-NMR spectroscopy. The NDMA/methacrylic ester copolymers decreased the surface tension of water in the order: C₄ = C₆ > C₈ > C₁₂ > C₁₆ > C₂ = C₁₈ > P(NDMA), lowest surface tension (35 dyn/cm) to highest surface tension (59 dyn/cm).     

Synthesis, characterization and biodegradation studies of poly(ester urethane)s

Bis-isocyanoto polyester was synthesized by the polymerization of PPSe with MDI and reacted with 1,3-propanediol chain extender to obtain poly(ester urethane)s. The effect of chain extender and PPSe content in polyurethane was investigated. The polymers were characterized by ¹H NMR, FT-IR, viscosity measurement, TGA and XRD. Their biodegradability was investigated by the hydrolytic degradation in NaOH solution (3% and 10%); enzymatic degradation by Rhizopus delemar lipase and soil burial degradation using garden-composted soil. Furthermore, the degraded film was characterized by molecular weight, intrinsic viscosity, DSC, XRD, FT-IR and surface morphology by SEM. The biodegradation study revealed that hydrolysis and soil burial degradation affected morphology of the PEUs. Hydrophobicity and hard segment seem to resist the hydrolytic and enzymatic degradability of PEU. Hydrolytic degradation was very rapid in 3% and 10% NaOH solutions at 37 °C, within 2 days 20% weight loss was observed. PEUs showed a much slower degradation rate under the R. delemar lipase at 37 °C. Experimental data showed that as soft segment increases biodegradation rate decreased. A significant rate of degradation was occurred in all PEU samples under soil burial condition. Surface morphology, which interconnected to good adhesion of bacteria on polymer surface, is considered to be a factor sensible for the biodegradation rate under soil burial condition.     

Influence of temperature,molecular weight,and molecular weight dispersity on the surface tension of PS,PP, and PE. I. Experimental

In this work, the influence of temperature, molecular weight (M?_n), and molecular weight dispersity (MWD) on the surface tension of polystyrene (PS) was evaluated using the pendant drop method. The influence of temperature on the surface tension of isotatic polypropylene (i‐PP) and of linear low‐density polyethylene (LLDPE) was also studied here. It was shown that surface tension decreases linearly with increasing temperature for all the polymers studied. The temperature coefficient ?dγ/dT (where γ is the surface tension, and T, the temperature) was shown to decrease with increasing molecular weight and to increase with increasing MWD. The surface tension of PS increased when the molecular weight was varied from 3400 to 41,200 g/mol. When the molecular weight of PS was further increased, the surface tension was shown to level off. The surface tension was shown to decrease with increasing molecular weight distribution. Contact angles formed by drops of diiomethane and water on films of PS with different molecular weights were measured at 20°C. The surface energies of those polymers were then evaluated using the values of the different pairs of contact angles obtained here using two different models: the harmonic mean equation and the geometric mean equation. It was shown that the values of the surface energy obtained are slightly less than are the ones extrapolated from surface‐tension measurements in the rubbery state. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1907–1920, 2001     

Synthesis and Physicochemical Properties of Alanine-Based Surfactants

The synthesis of a homologous series of alanine-based surfactants, namely sodium salts of n-alkanesulfonamido-2-propanoic acids in which n-alkane is n-dodecane, n-tetradecane, n–hexadecane, and n-octadecane having the formula RSO₂NHCH (CH₃)COO^?Na⁺, is described. The starting materials used were a mixture of secondary positional isomers of n-alkanesulfonyl chlorides obtained by photosulfochlorination reaction using sulfuryl chloride and a catalyst. Surface properties of the aqueous solutions of the synthesized surfactants, including the critical micelle concentration and minimal surface tension δ_min, were determined using surface tension measurements at 25 °C. The surface excess Γ and minimum area per molecule (A _min) where calculated using the Gibbs equation. The foaming power was also determined by the Bartsh method, and the R ₅ parameter was calculated to estimate the stability of the foam formed. The results obtained were compared to those of a commercial surfactant, sodium dodecylsulfate, and a series of synthesized glycine-based surfactants. The results obtained clearly show that the alanine-based surfactants possess good surface properties. The investigations highlight the influence on the surface properties of the addition of a methyl group in the hydrophilic part.     

Synthesis of copolymers of N,N-dimethyl acrylamide and methacrylate esters and their surface tensions

A systematic study of the preparation of N,N-dimethylacrylamide (NDMA)/methacrylic ester statistical copolymers was conducted. The methacrylic ester comonomers used in the copolymerizations were ethyl, n-butyl, n-hexyl, n-octyl, n-dodecyl, n-hexadecyl, and n-octadecyl methacrylates. It was found that the NDMA copolymers could be prepared in three molecular weight regions 1.0 × 10⁴, 2.0 × 10⁵, and greater than 1.0 × 10⁶ ([η] in water at 30°C of 0.1, 0.6, and greater than 1.5 dL/g, respectively). The molecular weights of the copolymers were dependent on the solvent employed in the polymerizations and on the presence of chain transfer agent (t-dodecyl mercaptan). All copolymer compositional analyses were made by 400 MH_z ¹H-NMR spectroscopy. The NDMA/methacrylic ester copolymers decreased the surface tension of water in the order: C₄ = C₆ > C₈ > C₁₂ > C₁₆ > C₂ = C₁₈ > P(NDMA), from lowest surface tension (35 dyn/cm) to highest surface tension (59 dyn/cm).     

Viscosity index. I. Evaluation of selected copolymers incorporating n-octadecyl acrylate as viscosity index improvers

Compositionally and structurally varied copolymers all containing n-octadecyl acrylate were prepared and evaluated as viscosity index improvers in a common base oil under conditions of low shear. Systems evaluated over a range of copolymer and blend composition were: copolymers of n-octadecyl acrylate with, respectively, methyl methacrylate, 2-ethylhexyl acrylate, and n-dodecyl acrylate; and homopolymers of poly(n-octadecyl acrylate), prepared with a wide range of molecular weights. Properties were compared with those of blends of commercial methacrylate copolymers (acryloids) which had been freed of their entraining liquid. Mixtures of base oil with copolymers of n-octadecyl acrylate and methyl methacrylate, compared at fixed SAE viscosities, were the most efficient of all blends studied. They had the smallest rate of change of viscosity with temperature (as measured by their ASTM slopes), particularly in the composition region of incipient polymer precipitation at room temperature. Efficiency of certain of these composition was somewhat greater than that of the acryloids. A parameter that related concentration and weight-average molecular weight was used to correlate all of the data for ASTM slope and viscosity. Empirical relations developed by using this parameter enabled rheological data to be estimated that agree within 6% of experimental values for the case of thermodynamically good base oil solvents. These data demonstrated the relatively small contributions of copolymer structure to viscosity index improvement.     

Surface changes in polyhydroxyalkanoate films during biodegradation and biofouling

BACKGROUND: Despite the recognition that microbial biofilms play a role in environmental degradation of bioplastics, few studies investigate the relationship between bioplastic biodegradation and microbial colonisation. We have developed protocols based on a combination of confocal laser scanning microscopy and contact angle goniometry to qualitatively and quantitatively map surface changes due to biofilm formation and biopolymer degradation of solvent cast poly(3‐hydroxyalkanoate) films in an accelerated in vitro biodegradation system. RESULTS: A significant regression relationship between biofilm formation and polymer biodegradation (R² = 0.96) was primarily conducted by cells loosely attached to the film surfaces (R² = 0.95), rather than the strongly attached biofilm (R² = 0.78). During biodegradation the surface rugosity of poly(3‐hydroxybutyrate) and poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] increased by factors of 1.5 and 1.76, respectively. In contrast, poly(3‐hydroxyoctanoate) films showed little microbial attachment, negligible weight loss and insignificant changes in surface rugosity. CONCLUSION: A statistically significant link is established between polymer weight loss and biofilm formation. Our results suggest that this degradation is primarily conducted by cells loosely attached to the polymer rather than those strongly attached. Biofilm formation and its type are dependent upon numerous factors; the flat undifferentiated biofilms observed in this study produce a gradual increase in surface rugosity, observed as an increase in waviness. Copyright © 2008 Society of Chemical Industry     

Surface activity of quaternary ammonium salts derived from jojoba oil

A number ofcis andtrans quatenary ammonium salts were synthesized from jojoba oil. All derivatives were found to be surface active agents, i.e., they reduced the surface tension to 35 dynes/cm⁻¹, at very low concentrations. The relationship between the surface activity and the molecular structure is discussed.