Effects of rhamnolipids on cell surface hydrophobicity of PAH degrading bacteria and the biodegradation of phenanthrene

Influence of saponins on the biodegradation of halogenated phenols

Biotransformation of aromatic compounds is a challenge due to their low aqueous solubility and sorptive losses. The main obstacle in this process is binding of organic pollutants to the microbial cell surface. To overcome these, we applied saponins from plant extract to the microbial culture, to increase pollutants solubility and enhance diffusive massive transfer. This study investigated the efficiency of Quillaja saponaria and Sapindus mukorossi saponins-rich extracts on biodegradation of halogenated phenols by Raoultella planticola WS2 and Pseudomonas sp. OS2, as an effect of cell surface modification of tested strains. Both strains display changes in inner membrane permeability and cell surface hydrophobicity in the presence of saponins during the process of halogenated phenols biotransformation. This allows them to more efficient pollutants removal from the environment. However, only in case of the Pseudomonas sp. OS2 the addition of surfactants to the culture improved effectiveness of bromo-, chloro- and fluorophenols biodegradation. Also introduction of surfactant allowed higher biodegradability of halogenated phenols and can shorten the process. Therefore this suggests that usage of plant saponins can indicate more successful halogenated phenols biodegradation for selected strains.

Monitoring dihydrodiol polyaromatic hydrocarbon metabolites produced by the freshwater microalgae Selenastrum capricornutum

We found that microalgae exposed to a mixture of polycyclic aromatic hydrocarbons (PAHs) did not show growth inhibition. Thus, we assumed that they could metabolize these compounds. In this study, the dihydrodiol-type PAH metabolites of benzo(a)pyrene (BaP), benzo(a)anthracene (BaA), benzo(b)fluoranthene (BbF) and benzo(k)fluoranthene (BkF) produced by the freshwater microalgae Selenastrum capricornutum were monitored and quantified using high-performance liquid chromatography with fluorescence detection (HPLC-FD) techniques. Exposure bioassays with S. capricornutum were performed using a 266 ng mL(-1) mixture of PAHs at different exposure times (0.75, 1, 3, 8, 16, 24 and 48 h) under controlled temperature (25 °C); the dihydrodiol metabolites formed in the liquid medium and the biomass were quantified. Metabolite identities were confirmed using HPLC-mass spectrometry; most of the metabolites formed were derived from BaA degradation. At 48 h after exposure 5,6-dBaA and 8,9-dBaA/10,11-dBaA were present in the liquid medium at 20% and 67% of the initial mass of BaA, respectively. Three metabolites of BaP were monitored in the liquid medium and biomass and, at 24 h, 4,5-dBaP accounted for 19%; , 7,8-dBaP, 5%; and 9,10-dBaP, 5% relative to the initial BaP mass. Microalgae exposed to BbF showed the presence of 1,2-dBbF and 9,10-dBbF (at 0.3% and 0.1% of the initial BbF mass, respectively) and those exposed to BkF produced 8,9-dBkF (6.5% of the initial BkF mass) in the liquid medium. Seven unknown compounds were formed after exposure; two compounds were identified as the metabolites of BaA and BaP. The results could facilitate the elucidation of the controversial biodegradation mechanism in microalgae.

Simultaneous Biodegradation of Phenol and n-Hexadecane by Cryogel Immobilized Biosurfactant Producing Strain Rhodococcus wratislawiensis BN38

The capability of the biosurfactant-producing strain Rhodococcus wratislawiensis BN38 to mineralize both aromatic and aliphatic xenobiotics was proved. During semicontinuous cultivation 11 g/l phenol was completely degraded within 22 cycles by Rhodococcus free cells. Immobilization in a cryogel matrix was performed for the first time to enhance the biodegradation at multiple use. A stable simultaneous hydrocarbon biodegradation was achieved until the total depletion of 20 g/l phenol and 20 g/l n-hexadecane (40 cycles). The alkanotrophic strain R. wratislawiensis BN38 preferably degraded hexadecane rather than phenol. SEM revealed well preserved cells entrapped in the heterogeneous super-macroporous structure of the cryogel which allowed unhindered mass transfer of xenobiotics. The immobilized strain can be used in real conditions for the treatment of contaminated industrial waste water.

Nonionic surfactants induced changes in cell characteristics and phenanthrene degradation ability of Sphingomonas sp. GY2B

Surfactant-mediated bioremediation has been widely applied in decontaminating PAH-polluted sites. However, the impacts of surfactants on the biodegradation of PAHs have been controversial in the past years. To gain a clear insight into the influencing mechanisms, three nonionic surfactants (Tween80, TritonX-100 and Brij30) were selected to systematically investigate their effects on cell surface properties (membrane permeability, functional groups and elements), cell vitality as well as subsequent phenanthrene degradation ability of Sphingomonas sp. GY2B. Results showed that biodegradation of phenanthrene was stimulated by Tween80, slightly inhibited by TritonX-100 and severely inhibited by Brij30, respectively. Positive effect of Tween80 may arise from its role as the additional carbon source for GY2B to increase bacterial growth and activity, as demonstrated by the increasing viable cells in Tween80 amended degradation systems determined by flow cytometry. Although TritonX-100 could inhibit bacterial growth and disrupt cell membrane, its adverse impacts on microbial cells were weaker than Brij30, which may result in its weaker inhibitive extent. Results from this study can provide a rational basis on selecting surfactants for enhancing bioremediation of PAHs.

Effect of natural and synthetic surfactants on crude oil biodegradation by indigenous strains

Hydrocarbon pollution is a worldwide problem. In this study, five surfactants containing SDS, LAS, Brij 30, Tween 80 and biosurfactant were used to evaluate their effect on crude oil biodegradation. Hydrocarbon degrading bacteria were isolated from oil production water. The biosurfactant used was a kind of cyclic lipopeptide produced by Bacillus subtilis strain WU-3. Solubilization test showed all the surfactants could apparently increase the water solubility of crude oil. The microbial adhesion to the hydrocarbon (MATH) test showed surfactants could change cell surface hydrophobicity (CSH) of microbiota, depending on their species and concentrations. Microcalorimetric experiments revealed these surfactants exhibited toxicity to microorganisms at high concentrations (above 1 CMC), except for SDS which showed low antibacterial activity. Surfactant supplementation (about 0.1 and 0.2 CMC) could improve degradation rate of crude oil slightly, while high surfactant concentration (above 1 CMC) may decrease the degradation rate from 50.5% to 28.9%. Those findings of this work could provide guidance for the application of surfactants in bioremediation of oil pollution.

Crude oil biodegradation aided by biosurfactants from Pseudozyma sp. NII 08165 or its culture broth

The aim of this work was to evaluate the biosurfactants produced by the yeast Pseudozyma sp. NII 08165 for enhancing the degradation of crude oil by a model hydrocarbon degrading strain, Pseudomonas putida MTCC 1194. Pseudozyma biosurfactants were supplemented at various concentrations to the P. putida culture medium containing crude oil as sole carbon source. Supplementation of the biosurfactants enhanced the degradation of crude oil by P. putida; the maximum degradation of hydrocarbons was observed with a 2.5 mg L(-1) supplementation of biosurfactants. Growth inhibition constant of the Pseudozyma biosurfactants was 11.07 mg L(-1). It was interesting to note that Pseudozyma sp. NII 08165 alone could also degrade diesel and kerosene. Culture broth of Pseudozyma containing biosurfactants resulted up to ∼46% improvement in degradation of C10-C24 alkanes by P. putida. The enhancement in degradation efficiency of the bacterium with the culture broth supplementation was even more pronounced than that with relatively purer biosurfactants.

Enhancement of nitrate-induced bioremediation in marine sediments contaminated with petroleum hydrocarbons by using microemulsions

The effect of microemulsion on the biodegradation of total petroleum hydrocarbons (TPH) in nitrate-induced bioremediation of marine sediment was investigated in this study. It was shown that the microemulsion formed with non-ionic surfactant polyoxyethylene sorbitan monooleate (Tween 80), 1-pentanol, linseed oil, and either deionized water or seawater was stable when subjected to dilution by seawater. Desorption tests revealed that microemulsion was more effective than the Tween 80 solution or the solution containing Tween 80 and 1-pentanol to desorb TPH from marine sediment. In 3 weeks of bioremediation treatment, the injection of microemulsion and NO3 (-) seems to have delayed the autotrophic denitrification between NO3 (-) and acid volatile sulfide (AVS) in sediment compared to the control with NO3 (-) injection alone. However, after 6 weeks of treatment, the delaying effect of microemulsion on the autotrophic denitrification process was no longer observed. In the meantime, the four injections of microemulsion and NO3 (-) resulted in as high as 29.73 % of TPH degradation efficiency, higher than that of two injections of microemulsion and NO3 (-) or that of four or two injections of NO3 (-) alone. These results suggest that microemulsion can be potentially applied to enhance TPH degradation in the nitrate-induced bioremediation of marine sediment.

Gene expression of an arthrobacter in surfactant-enhanced biodegradation of a hydrophobic organic compound

Surfactants can affect the biodegradation process and the fate of hydrophobic organic compounds (HOCs) in the environment. Previous studies have shown that surfactants can enhance the biodegradation of HOCs by increasing cell surface hydrophobicity (CSH) and membrane fluidity. In this study, we took this work one step further by investigating the expression levels of three genes of Arthrobacter sp. SA02 in the biodegradation of phenanthrene as a typical HOC at different concentrations of sodium dodecyl benzenesulfonate (SDBS), which is a widely used surfactant. The Δ9 fatty acid desaturase gene codes for Δ9 fatty acid desaturase, which can convert saturated fatty acid to its unsaturated form. The ring-hydroxylating dioxygenase (RHDase) and the 1-hydroxyl-2-naphthoate dioxygenase (1H2Nase) genes code for the RHDase and 1H2Nase enzymes, respectively, which play a key role in decomposing doubly hydroxylated aromatic compounds. The results show that these three genes were upregulated in the presence of SDBS. On the basis of the genetic and physiological changes, we proposed a pathway that links the gene expression with the physiological phenomena, including CSH, membrane fluidity, and intracellular degradation. This study advances our understanding of the surfactant-enhanced biodegradation of HOCs at the gene level, and the proposed pathway should be further validated in the future.

Hydrocarbon degradation by a newly isolated thermophilic Anoxybacillus sp. with bioemulsifier production and new alkB genes

In this work, a new thermophilic bacterial strain was isolated and identified asAnoxybacillussp. WJ-4. This strain of WJ-4 can degrade a wide range of hydrocarbons, and production of an oligosaccharide–lipid–peptide bioemulsifier was detected.

Biodegradation of aliphatic hydrocarbons in the presence of hydroxy cucurbit[6]uril

Aliphatic hydrocarbons are one of the major environmental pollutants with reduced bioavailability. The present study focuses on the effect of hydroxy cucurbit[6]uril on the bioavailability of hydrocarbons. A bacterial consortium was used for biodegradation studies under saline and non-saline conditions. Based on denaturing gradient gel electrophoresis results it was found that the consortium under saline conditions had two different strains. The experiment was conducted in microcosms with tetradecane, hexadecane, octadecane and mixture of the mentioned hydrocarbons as the sole carbon source. The residual hydrocarbon was quantified using gas chromatography every 24h. It was found that biodegradation of tetradecane and hexadecane, as individual carbon source increased in the presence of hydroxy CB[6], probably due to the increase in their bioavailability. In case of octadecane this did not happen. Bioavailability of all three aliphatic hydrocarbons was increased when provided as a mixture to the consortium under saline conditions.

Effect of surfactant on phenanthrene metabolic kinetics by Citrobacter sp. SA01

To attain a better understanding of the effects of surfactants on the metabolic kinetics of hydrophobic organic compounds, the biodegradation of phenanthrene by Citrobacter sp. SA01 was investigated in a batch experiment containing Tween 80, sodium dodecyl benzene sulfonate and liquid mineral salt medium. The Monod model was modified to effectively describe the partition, phenanthrene biodegradation and biopolymer production. The results showed that Tween 80 and sodium dodecyl benzene sulfonate (each at 50mg/L) enhanced phenanthrene metabolism and poly-β-hydroxybutyrate production as indicated by the increasing amounts of intermediates (by 17.2% to 47.9%), and percentages of poly-β-hydroxybutyrate (by 107.3% and 33.1%) within the cell dry weight when compared to their absence. The modified Monod model was capable of predicting microbial growth, phenanthrene depletion and biopolymer production. Furthermore, the Monod kinetic coefficients were largely determined by the surfactant-enhanced partition, suggesting that partitioning is a critical process in surfactant-enhanced bioremediation of hydrophobic organic compounds.

Surfactant-modified fatty acid composition of Citrobacter sp. SA01 and its effect on phenanthrene transmembrane transport

The effects of the surfactants, Tween 80 and sodium dodecyl benzene sulfonate (SDBS) on a membrane's fatty acid composition and the transmembrane transport of phenanthrene were investigated. The results indicated that both surfactants could modify the composition of fatty acids of Citrobacter sp. Strain SA01 cells, 50 mg L(-1) of both surfactants changed the composition of the fatty acids the most, increasing the amount of unsaturated fatty acids. The comparison of fatty acid profiles with diphenylhexatriene fluorescence anisotropy, a probe for plasma membrane fluidity, suggested that an increased amount of unsaturated fatty acids corresponded to greater membrane fluidity. In addition, increased unsaturated fatty acids promoted phenanthrene to partition from the extracellular matrix to cell debris, which increased reverse partitioning from the cell debris to the cytochylema. The results of this study were expected in that the addition of a surfactant is a simple and effective method for accelerating the rate-limiting step of transmembrane transport of hydrophobic organic compounds (HOCs) in bioremediation.

Microcalorimetric investigation of the effect of non-ionic surfactant on biodegradation of pyrene by PAH-degrading bacteria Burkholderia cepacia

Polycyclic aromatic hydrocarbons (PAHs) are widespread in various ecosystems and are pollutants of great concern due to their potential toxicity, mutagenecity and carcinogenicity. Surfactant has become a hot topic for its wide application in the bioremediation of PAHs. The aim of this work is to explore a microcalorimetric method to determine the toxic effect of pyrene on Bacillus subtilis (B. subtilis) and the PAH-degrading bacteria Burkholderia cepacia (B. cepacia) and to evaluate the effect of Tween 80 on biodegradation of pyrene. Power-time curves were studied and calorimetric parameters including the growth rate constant (k), half inhibitory concentration (IC₅₀), and total thermal effect (Q(T)) were determined. B. subtilis, B. cepacia and B. cepacia with Tween 80 were completely inhibited when the concentration of pyrene were 200, 800 and 1600 µg mL⁻¹, respectively. B. cepacia shows better tolerance to pyrene than B. subtilis. Tween 80 significantly improves the biodegradation of pyrene by increasing the bioavailability of pyrene. In addition, the expression of catechol 2,3-dioxygenase (C23O) in B. cepacia is responsible for the degradation of pyrene and plays an important role in improving the biodegradation of pyrene. Moreover, the activity of C23O increases with the application of Tween 80. The enhanced bioavailability and biodegradation of pyrene by Tween 80 shows the potential use of Tween 80 in the PAHs bioremediation.

Influences and mechanisms of surfactants on pyrene biodegradation based on interactions of surfactant with a Klebsiella oxytoca strain

Surfactant-enhanced bioremediation has been proposed as a promising technology for the treatment of organic polluted soils; however its application has been hindered by the controversial influences and mechanisms of surfactants on the biodegradation of hydrophobic organic compounds. To address this problem, effects of five surfactants on the sorption and biodegradation of pyrene by Klebsiella oxytoca PYR-1, as well as their interactions with bacterial cell surface and membrane lipids were investigated. We found that surfactants enhanced or inhibited pyrene biodegradation depending on their effects on the sorption of pyrene onto bacterial cell, which occurred mainly through modifying cell surface hydrophobicity (such as Tween series surfactants) or disrupting bacterial membrane (such as Triton X-100), respectively. A relatively high positive correlation (P<0.0001) was observed between biodegradation promotion (Bs/B0) and enhancement of sorption coefficients (Kd,s(∗)/Kd,0(∗)) for pyrene in the presence of surfactant, indicating that surfactant-induced sorption played the dominant role during pyrene biodegradation.

Modification of surface and enzymatic properties of Achromobacter denitrificans and Stenotrophomonas maltophilia in association with diesel oil biodegradation enhanced with alkyl polyglucosides

The article concerns the influence of selected alkyl polyglucosides on biodegradation, cell surface and enzymatic properties of Stenotrophomonas maltophilia and Achromobacter denitrificans. The biodegradation of diesel oil depends on several factors including type and the amount of surfactant as well as bacterial genera used in the process. Nevertheless, a careful selection of these variables must be made as some bacterial strains prefer to use surfactants as their carbon source. This leads to the lowered biodegradation of diesel oil as can be observed for the tested S. maltophilia strain. Alkyl polyglucosides influenced the cell surface properties of both of the tested strains in slightly different ways. Especially for A. denitrificans, for which the hydrophobicity increased with concentration of both--Lutensol GD 70 and Glucopon 215 in diesel oil-surfactant systems. Moreover, judging by the efficiency of biodegradation, the most effective process was observed in the presence of Lutensol GD 70 (240 and 360 mg L(-1)) with biodegradation rising from 32% (without surfactant) to 68%. No such relation was observed for S. maltophilia.

Characterization of rhamnolipids produced by non-pathogenic Acinetobacter and Enterobacter bacteria

Rhamnolipid production by two non-pathogenic bacterial strains Acinetobacter calcoaceticus and Enterobacter asburiae, and established rhamnolipid producer Pseudomonas aeruginosa was investigated. Rhamnolipids were separated from supernatant and further purified by thin-layer chromatography. Mass spectrometry with negative electrospray ionization revealed rhamnolipid homologues varying in chain length and unsaturation. Tandem mass spectrometry identified mono-rhamnolipid and di-rhamnolipid homologues containing one or two 3-hydroxy fatty acids. Several media differing in carbon (sunflower oil, glycerol and sodium citrate), nitrogen (ammonium ions, nitrate) and phosphorus (total content) source, respectively, were tested to obtain enhanced rhamnolipid production. The best production (0.56g/l) was obtained when nitrate was used as a nitrogen source. Both strains produced rhamnolipids that exhibited excellent emulsification activity with aromatic and aliphatic hydrocarbons and several plant oils. Unlike P. aeruginosa the two strains, i.e. Acinetobacter and Enterobacter, are not pathogenic to humans.

Effect of surfactant-induced cell surface modifications on electron transport system and catechol 1,2-dioxygenase activities and phenanthrene biodegradation by Citrobacter sp. SA01

In order to better understand how surfactants affect biodegradation of hydrophobic organic compounds (HOCs), Tween 80 and sodium dodecyl benzene sulfonate (SDBS), were selected to investigate effects on cell surface hydrophobicity (CSH), electron transport system (ETS) activities and phenanthrene biodegradation by Citrobacter sp. SA01. Tween 80 and SDBS increased CSH by 19.8-25.2%, ETS activities by 352.1-376.0μmol/gmin, catechol 1,2-dioxygenase (C12) activities by 50.8-52.7U/L, and phenanthrene biodegradation by 8.9-17.2% separately in the presence of 50mg/L of surfactants as compared to in their absence. Lipopolysaccharide (LPS) release was 334.7μg/mg in the presence of both surfactants whereas in their absence only 8.6-44.4μg/mg of LPS was released. Thus, enhanced LPS release probably increased ETS and C12 activities as well as phenanthrene biodegradation by increasing CSH. The results demonstrate that surfactant-enhanced CSH provides a simple, yet effective strategy for field applications of surfactant-enhanced bioremediation of HOCs.

Genetic and chemical analyzes of transformations in compost compounds during biodegradation of oiled bleaching earth with waste sludge

Composting of oiled bleaching earth with waste sludge and corn straw was carried out to investigate the ability of microorganisms to synthesize biosurfactants that might decrease the surface tension of composts. Analytical results and changes in the surface tension suggest that biodegradation of fatty by-products was the consequence of emulsifying properties of higher fatty acids. The surface tension for isolates from all composting phases was between 37 and 43 mN m(-1). No substances synthesized by microorganisms that might be able to decrease the surface tension were detected in composts. Tensammetric, TLC and HPLC-MS results and changes in surface tension suggest that biodegradation of fatty by-products results from the emulsifying properties of higher fatty acids. A decrease in fatty content from 144 to 6 mg g(-1) dry matter was obtained.

Effects of Tween 80 on the removal, sorption and biodegradation of pyrene by Klebsiella oxytoca PYR-1

The sorption and biodegradation of pyrene by Klebsiella oxytoca PYR-1 (PYR-1) in the presence of nonionic surfactant Tween 80 were investigated toward a better understanding that how surfactants can affect biodegradation of hydrophobic organic compounds. The results indicated that Tween 80 can promote the removal, sorption and biodegradation of pyrene depending on the surfactant concentration, of which the most significant promotion of biodegradation was achieved at critical micelle concentration of Tween 80 with an improvement of 22.4%. A highly positive correlation (P<0.0001) was observed between the biodegradation and sorption of pyrene with the presence of Tween 80. Biosorption experiments showed the same trends as biodegradation and further illustrated the improved biodegradation of pyrene was mainly due to surfactant-facilitated sorption. The regularly changes of cell surface hydrophobicity suggested formation of more hydrophobic surface caused by surfactant sorption lead to stimulation of pyrene sorption.

Enhanced anoxic bioremediation of PAHs-contaminated sediment

In this study, the biodegradation of 16 polycyclic aromatic hydrocarbons (PAHs) in marine sediment was investigated under three different anoxic conditions, i.e. sulfate-only, nitrate-only and mixed nitrate/sulfate as electron acceptors. All two-, three- and four-ring PAHs showed significant biodegradation with the removal efficiencies ranging from 42% to 77%, while five- and six-ring PAHs showed little degradation. The results illustrated that two- to three-ring PAHs could be degraded at a rate of 4.01×10(-2)-6.42×10(-2) d(-1) under nitrate-reducing condition, faster than that of under sulfate-reducing condition. Biodegradation of two- and three-ring PAHs followed first-order model well with the rate constants of 1.62×10(-2)-6.42×10(-2) d(-1). The biodegradation of four ring PAHs followed the zero-order kinetic model with the rate constants of 1.26×10(-2)-2.22×10(-2) mg/kg/d. Molecular analysis indicated that nahAc gene increased by two orders of magnitude during the biodegradation and served as a good indicator of PAHs-degrading bacterial population and biodegradation process.

Alteration in cell surface properties of Burkholderia spp. during surfactant-aided biodegradation of petroleum hydrocarbons

Chemical surfactants may impact microbial cell surface properties, i.e., cell surface hydrophobicity (CSH) and cell surface charge, and may thus affect the uptake of components from non-aqueous phase liquids (NAPLs). This work explored the impact of Triton X-100, Igepal CA 630, and Tween 80 (at twice the critical micelle concentration, CMC) on the cell surface characteristics of Burkholderia cultures, Burkholderia cepacia (ES1, aliphatic degrader) and Burkholderia multivorans (NG1, aromatic degrader), when grown on a six-component model NAPL. In the presence of Triton X-100, NAPL biodegradation was enhanced from 21% to 60% in B. cepacia and from 18% to 53% in B. multivorans. CSH based on water contact angle (50-52°) was in the same range for both strains while zeta potential at neutral pH was -38 and -31 mV for B. cepacia and B. multivorans, respectively. In the presence of Triton X-100, their CSH increased to greater than 75° and the zeta potential decreased. This induced a change in the mode of uptake and initiated aliphatic hydrocarbon degradation by B. multivorans and increased the rate of aliphatic hydrocarbon degradation in B. cepacia. Igepal CA 630 and Tween 80 also altered the cell surface properties. For B. cepacia grown in the presence of Triton X-100 at two and five times its CMC, CSH increased significantly in the log growth phase. Growth in the presence of the chemical surfactants also affected the abundance of chemical functional groups on the cell surface. Cell surface changes had maximum impact on NAPL degradation in the presence of emulsifying surfactants, Triton X-100 and Igepal CA630.

Hydrocarbon degradation and bioemulsifier production by thermophilic Geobacillus pallidus strains

Geobacillus pallidus XS2 and XS3 were isolated from oil contaminated soil samples in Yumen oilfield, China, and were able to produce bioemulsifiers on different hydrocarbons. Biodegradation assays exhibited that approximately 70% of PAH (250 mg/L) or 85% of crude oil (500 mg/L) was removed by the thermophilic bacteria after 20 days. The bioemulsifiers of the two strains were isolated and obtained a productive yield of 4.24±0.08 and 3.82±0.11g/L, respectively. GPC analysis revealed that the number-average molecular weights (M(n)) of the two bioemulsifiers were 271,785 Da and 526,369 Da, with PDI values of 1.104 and 1.027, respectively. Chemical composition studies exhibited that the bioemulsifier XS2 consisted of carbohydrates (68.6%), lipids (22.7%) and proteins (8.7%) while the bioemulsifier XS3 was composed by carbohydrates (41.1%), lipids (47.6%) and proteins (11.3%). Emulsification assays approved the effectiveness of bioemulsifiers over a wide range of temperature, pH and salinity.

Novel lipopeptide biosurfactant produced by hydrocarbon degrading and heavy metal tolerant bacterium Escherichia fergusonii KLU01 as a potential tool for bioremediation

Escherichia fergusonii KLU01, a propitious bacterial strain isolated from oil contaminated soil was identified to be hydrocarbon degrading, heavy metal tolerant and a potent producer of biosurfactant using diesel oil as the sole carbon and energy source. The biosurfactant produced by the strain was characterized to be a lipopeptide. The minimum active dose and critical micelle concentration of the biosurfactant were found as 0.165±0.08 μg and 36 mg/L, respectively. In spite of being an excellent emulsifier, the biosurfactant showed an incredible stability at extremes of temperature, pH and at various concentrations of NaCl, CaCl₂ and MgCl₂. Also the bacterium manifested tolerance towards Manganese, Iron, Lead, Nickel, Copper and Zinc. The strain emerges as a new class of biosurfactant producer with potential environmental and industrial applications, especially in hydrocarbon degradation and heavy metal bioremediation.