Surface Tension Of Medium Research Articles

Combination of Mollase and Glucose as Substrate for The Production of Biosurfactant by Bacillus subtilis BK7.1

Biosurfactant is a secondary metabolite which has properties and structures such as surfactants that are able to decrease surface tension water and cause microsolubilization or emulsification. Biosurfactants are active compounds that are produced at the microbial cell surface or excreted especially Bacillus. Previous research reported that B. subtilis BK7.1 had ability to form biosurfactant. In this study, B. subtilis BK7.1 produced biosurfactant using a combination of molasse and glucose as a carbon source. The purpose of study was characterized biosurfactant from B. subtilis BK7.1 by counting the emulsification index and the surface tension of supernatant, calculating (CMC) value, and examining stability of biosurfactant. B. subtilis BK7.1 could produce the biosurfactant from molasse and glucose with CMC value was about 4 g/L. Biosurfactant of B. subtilis BK7.1 could reduce the surface tension of medium from 54.68 to 49.2 mN/m, emulsify kerosene around 15.8%, had temperature stability in the range of 27⁰C to 45⁰C, and had stability at pH 6. This study showed that the use of molasses waste combined with glucose in biosurfactant production was very efficient and had potential for further applications.

Facile fabrication of regenerable spherical La0.8Ce0.2MnO3 pellet via wet-chemistry molding strategy for elemental mercury removal

Perovskite-based sorbents have received extensive attention in the field of mercury abatement. However, the excellent Hg0 adsorption performance on the lab scale hardly transforms into industrial-scale utilization because of the elutriation and microcrystalline nature of powdery perovskite sorbent. Hence, the granulation of perovskite into pellets is a strongly solicited and urgent demand. In this work, a universal granulation strategy is exploited for fabricating perovskite sorbent pellets for Hg0 capture from coal combustion flue gas (CCFG) based on a facile wet-chemistry method. This route takes advantages of the unique thermal sensitivity and thermal decomposition characteristics of agar powder and surface tension of medium to simultaneously trade off the molding, pore creation, and mechanical property of perovskite-based sorbent pellets. Besides, silica sol was also added to further enhance the physical strengths of sorbent pellets. The obtained perovskite sorbent pellet (i.e., LCMO-A-Z-2) with a favorable BET surface area of 113.16 m2 g−1 and pore diameter of 8.81 nm, largely facilitating Hg0 diffusion and capture over sorbent pellets. LCMO-A-Z-2 was further employed to Hg0 adsorption experiment under simulated CCFG, which exhibited satisfactory Hg0 adsorption capacity of 2.07 mg g−1 and nearly identical Hg0 adsorption performance after 5 cycles. The weight loss was approximately 13 % after 1000 rotations in the anti-attrition ability experiment suggesting its outstanding mechanical strength. It is reasonable to deduce this granulation method can be readily extended to other powdery sorbents. This work makes first step towards the application of sorbent pellets under application-relevant conditions and support the ultimate implementation of traditional sorbents in various large-scale industrial scenarios.

Isolation and screening of biosurfactant producing yeast from soil contaminated with oil

The present study was aimed to isolate yeasts from soil samples contaminated with oil and their ability to produce biosurfactants. Five samples were collected from different sites of Baghdad, thirty four isolate of yeasts were obtained from these contaminated soil. Nineteen isolates from them were able to produce biosurfactant according to the diameter of clearing zonein solution test, while other isolates gave negative results. The yeast isolates which gave positive result werequantitatively screened on the basis of emulsification index and surface tension, secondary screening showed that isolates SD5, SB8 and SK10 giving the highest yield of biosurfactant in their cultures and the values of emulsification index were 45.7%, 56.9% and 53.4% respectively. Also, the biosurfactant of isolates SD5, SB8 and SK10 were exhibited maximum ability to reduce the surface tension of medium to 38.2, 27.1 and 30.8 mN\m respectively. Finally selected isolates SD5, SB8 and SK10 were identification on the basis of morphological and biochemical tests, the results revealed that isolates were identified as Saccharomyces cerevisiaeSB8, Candida glabrataSD5 and Candida glabrata SK10 respectively.The three most active isolates were tested to see their ability to produce biosurfactant in BH medium supplemented with four types of agricultural residues (rice bran, banana peel, wheat bran and corn cobs) as a source of carbon compared with BH medium with glucose. All isolates showed good ability to produce biosurfactant in liquid medium with different types of agricultural wastes and also with glucose. Candida glabrata SD5 exhibited highest activity for biosurfactant production when grown on agricultural wastes and glucose depend on the values of emulsification index and surface tension, whilethe wheat bran as a substrate gave best stimulation for biosurfactant production compared with other agricultural wastes.

Characterization of tear dynamics

AbstractPurpose: Tear film is important in eye optics due to its influence on dry eye, contact lenses fit, etc. After blinking, it starts to evaporate causing the film to thin. While thinning in the eye center, the tear maintains a constant thickness around the eyelids (meniscus), which is easy to measure. This work aims to study tear film dynamics based on the meniscus and dry eye‐related parameters.Methods: A hybrid OCT‐iVue was used to measure the lower meniscus for several subjects. The dynamics of the tear were simulated with a precorneal tear film model after blinking [1], introducing the tear geometric parameters as well as physical parameters (viscosity, evaporation, surface tension, etc). The model uses the standard parameters given in [1], changing the values of the meniscus, viscosity, and surface tension to test different patients and dry eye conditions.Results: The tear film thickness was calculated for patients with the different meniscus. The model shows a tear thinning over time (additional drop before each meniscus). In the central eye, there are slight oscillations that are more pronounced for higher meniscus, increasing pressure. The greater meniscus seems to have greater spatial stability. The method allows the study of the spatial–temporal oscillations of tears and relates them to their physical parameters.Conclusions: Tear stability appears to be related to the ocular meniscus and greater stability is observed for the larger meniscus. Dry eye characteristics appear with high viscosity and medium surface tension. Additional mathematical studies should be done to clarify the influence of different tear parameters and their measure in different patients.Reference1. Braun R.J., et al. Modelling drainage of the precorneal tear film after a blink. Math Med Biol 2003; 20: 1–28.

Biosurfactant-Producing Mucor Strains: Selection, Screening, and Chemical Characterization

Biosurfactants are amphiphilic molecules with surface tension reducing activities. Among biosurfactant producers, fungi have been identified as promising organisms. While many studies have investigated biosurfactant production in fungal species from the Ascomycota and Basidiomycota phyla, less is known concerning species from the Mucoromycota phylum. In this context, the aim of this study was to screen and optimize biosurfactant production in 24 fungal strains, including seven Mucor, three Lichtheimia, and one Absidia species. After cultivation in a medium stimulating surfactant production, the surface activity of cell-free supernatants was measured using both oil spreading and parafilm M tests. Among them, five Mucor strain cell-free supernatants belonging to M. circinelloides, M. lanceolatus, M. mucedo, M. racemosus, and M. plumbeus, showed oil repulsion. Then, the impact of the medium composition on surfactant production was evaluated for eight strains. Three of them, i.e., Mucor circinelloides UBOCC-A-109190, Mucor plumbeus UBOCC-A-111133, and Mucor mucedo UBOCC-A-101353 showed an interesting surfactant production potential, reducing the medium surface tension to 36, 31, and 32 mN/m, respectively. A preliminary characterization of the surfactant molecules produced by these strains was performed and showed that these compounds belonged to the glycolipid family.

Application of Psychrotolerant Antarctic Bacteria and Their Metabolites as Efficient Plant Growth Promoting Agents.

Iron is the fourth most abundant element on earth. However, its low bioavailability is a key plant-growth limiting factor. Bacteria play an important role in plant growth promotion since they produce specific secondary metabolites that may increase macro- and micronutrient accessibility in soil. Therefore, bacterial-derived iron chelators, as well as surface-active compounds, are recognised as essential to plant welfare. In this study, three cold-active Antarctic bacterial strains, i.e. Pseudomonas sp. ANT_H12B, Psychrobacter sp. ANT_H59 and Bacillus sp. ANT_WA51, were analysed. The physiological and genomic characterisation of these strains revealed their potential for plant growth promotion, reflected in the production of various biomolecules, including biosurfactants (that may lower the medium surface tension of even up to 53%) and siderophores (including ANT_H12B-produced mixed-type siderophore that demonstrated the highest production, reaching the concentration of up to 1.065 mM), increasing the availability of nutrients in the environment and neutralising fungal pathogens. Tested bacteria demonstrated an ability to promote the growth of a model plant, alfalfa, increasing shoots’ length and fresh biomass even up to 26 and 46% respectively; while their metabolites increased the bioavailability of iron in soil up to 40%. It was also revealed that the introduced strains did not disrupt physicochemical conditions and indigenous soil microbial composition, which suggests that they are promising amendments preserving the natural biodiversity of soil and increasing its fertility.

Utilization of natural surfactants: An approach towards sustainable universe

AbstractA broad range of microorganisms produce biosurfactants, which are surface‐active compounds. They are molecules with both hydrophilic and hydrophobic domains that can lower the growth medium's surface tension and interfacial tension. Since they are nontoxic and biodegradable, biosurfactants can be used as a green substitute in various situations. Biosurfactants are also primarily used in the pharmaceutical and oil sectors, as well as in pollutant bioremediation. Aside from these, biosurfactants can be used in a wide range of food and agriculture industries, cosmetics, and skincare products. We sincerely hope that this review will help to understand the different applications of biosurfactants and their future potential.

Assessment of Rheological Behaviour of Water-in-Oil Emulsions Mediated by Glycolipid Biosurfactant Produced by Bacillus megaterium SPSW1001.

A screening programme using mineral salt medium supplemented with n-hexadecane resulted in isolating a Bacillus megaterium SPSW1001 which was capable of producing surface active molecules lowering culture medium surface tension to 27.43 ± 0.029 mN/m and interfacial tension to 0.38 ± 0.03 mN/m at 72h and an emulsification index (E24) (85.63%). The biosurfactant product was further used to assess its effects on the rheological characteristics of water-in-oil emulsion prepared with engine oil. Structural characterization of the biosurfactant product by FTIR revealed a C-O-C stretch in sugar moiety and ester carbonyl linkage group between sugar and fatty acids, respectively, while mass spectral analysis revealed its glycolipid nature, with an m/z value of 662.44. The fluid behaviour ofwater-in-oil emulsion showed a non-Newtonian viscoelastic dilatant flow after yielding exemplified appropriately by Herschel-Bulkley model with 100% confidence of fit. The present study is significant in formulation and handling, processing, and transport of emulsion and in understanding flocculation characteristics.

Isolation, screening, and extraction the more efficient local yeast isolates for biosurfactant production

Twelve samples of three spices of fruits (Kiwi, orange, and apple) and two spices of vegetables (Green pepper and cucumber) were collected from local shops and supermarkets to isolate the yeast using solid YEPG medium, twenty local yeast isolates were prepared from all samples, thereafter each isolate was tested for its ability to produce biosurfactant using liquid YEPG medium. Results have indicated that only three isolates had the ability to produce the biosurfactant at different abilities in growth medium depending on the emulsification index after 24 hr. They were tested for the production of extracellular biosurfactant only three isolates OS2, AS 9, and PS 14 were able to produce biosurfactant with emulsification index (E24) against machine oil 36%, 47% and 28% respectively also was capable to spread oil by 12mm, 20mm and 9mm respectively but they didn’t reduce YEPG medium surface tension significantly. The three isolates OS2, AS 9, and PS 14 were tested for intracellular biosurfactant, which gave the highest ability to emulsify both machine oil and crude oil, where the emulsification index (E24) reached 46%, 80%, and 55% towards motor oil and 50%, 100%, and 62% towards crude oil for the three isolates, respectively. According to these results, the isolate AS 9 was regarded as the best producer for biosurfactant and identified this isolate as a Saccharomyces cerevisiae. Thereafter this biosurfactant was partially purified using cold ethanol and left to dry using a Rotary evaporator and then converted into a powder by using a Freeze dryer.

Aggregation and adsorption properties of benzyldimethylhexadecylammonium tetrachloromanganate(II) metallosurfactant in water–ethylene glycol medium

The aggregation and adsorption properties of metallosurfactant, benzyldimethylhexadecylammonium tetrachloromanganate(II) (BDHA2[MnCl4], where BDHA represents benzyldimethylhexadecylammonium group) in binary aqueous mixtures of ethylene glycol (EG) were investigated by tensiometric, conductometric, dynamic light scattering (DLS) and transmission electron microscopy (TEM) methods at 298.15 K. The percentage of EG (by weight) was varied between 0 and 100%. The physicochemical properties determined and discussed include critical micelle concentration (cmc), counterion binding constant (β), Gibbs free energy of micellization (), surface excess at cmc (), minimum area per surfactant molecule (), surface pressure (πcmc), minimum free energies (G min) and size of aggregates. This study revealed that with increase in percentage of EG the cmc of BDHA2[MnCl4] metallosurfactant increases and the cmc of BDHA2[MnCl4] in EG is about 158 times higher than that in water. The counterion binding constant values increase with increase in percentage of EG from 10% to 70% and thereafter decrease. The adsorption of metallosurfactant at the air–solution interface decreases as the EG content in the bulk increases. The values were found to be negative and the negative value decreases with increase in percentage of EG. Gordon parameter and ratio of surface tension of medium to that of the metallosurfactant solution at cmc are used to represent solvophobicity of the medium. DLS measurements revealed that the hydrodynamic diameters (d H) of the micelles increase with increase in percentage of EG (in pure EG, d H = 28.3 nm). TEM measurements showed the presence of spherical micelles.

Enhancement of glycolipid production by Stenotrophomonas acidaminiphila TW3 cultivated in low cost substrate

This study aimed to investigate potential biosurfactant production of Stenotrophomonas acidaminiphila TW3 isolated from sediments contaminated with palm oil soapstocks using low cost substrates. The combination of central composite rotatable design (CCRD) and response surface methodology (RSM) was used to optimize biosurfactant production. The highest biosurfactant production (2.31 g/L) was obtained under the optimal conditions of 49.96 g/L used palm oil as a carbon source, 3.00 g/L NaNO 3 as a nitrogen source and medium pH 6.0. RSM increased the yield of biosurfactant up to 2.1 folds however, the productivity is still low further improvement is needed. The biosurfactant obtained from the S. acidaminiphila TW3 was able to lower the surface tension of medium from 72 to 32 mN/m. The biosurfactant was purified by liquid column chromatography and identified as glycolipid using thin layer chromatography, Fourier transform infrared spectroscopy, Mass spectrometer and Nuclear Magnetic Resonance. The biosurfactant could reduce surface tension of pure water to 32 mN/m with a critical micelle concentration of 0.2 g/L. It is an effective biosurfactant over a wide range of temperatures, pH and salt concentrations. Moreover, the biosurfactant showed ability to enhance PAHs solubility and removed used lubricating oil contaminated in sand. • The production of biosurfactant by strain TW3 was optimized by RSM methodology. • The biosurfactant produced by strain TW3 was identified as glycolipid. • Biosurfactant activity was stable under extreme conditions. • This glycolipid increased PAHs solubility and removed ULO.

Diversity of Metal-Resistant and Tensoactive-Producing Culturable Heterotrophic Bacteria Isolated from a Copper Mine in Brazilian Amazonia

Bacterial extracellular polymeric substances (EPSs) present diverse properties of biotechnological interest, such as surface modification, metal adsorption and hydrophobic substances solubilization through surface tension reduction. Thus, there is a growing demand for new producing strains and structurally variable biomolecules with different properties. One approach for scanning this biodiversity consists of exploring environments under selective pressures. The aim of this study was to evaluate the composition of culturable heterotrophic bacterial communities from five different sites from a copper mine in the Amazon biome by an enrichment technique to obtain metal resistant bacteria (lead, arsenic, cadmium, copper and zinc) capable of producing EPSs. The bacterial densities at the sites varied from 2.42 × 103 to 1.34 × 108 NMP mL−1 and the 77 bacterial isolates obtained were classified in four divisions, β-Proteobacteria (16.88%), γ-Proteobacteria (7.29%), Firmicutes (61%) and Actinobacteria (12.98%). Bacillus, Alcaligenes, and Lysinibacillus were the most dominant among the 16 observed genera, but the relative frequency of each varied according to the sample and the metal used in the enrichment culture. 58% of the bacterial strains (45) could produce EPSs. From these, 33 strains showed emulsifying activity (E24), and 9 of them reached values higher than 49%. Only Actinomyces viscosus E3.Pb5 and Bacillus subtilis group E3.As2 reduced the medium surface tension to values lower than 35 mN m−1. It was possible to confirm the high presence of bacteria capable of producing EPSs with tensoactive properties in Amazon copper mines and the evolutionary pressure exerted by the heavy metals during enrichment. These molecules can be tested as an alternative for use in processes that involve the removal of metals, such as the bioremediation of contaminated environments.

Production and formulation of a new low-cost biosurfactant to remediate oil-contaminated seawater

The aim of the present study was to produce biosurfactants using three bacterial strains (Pseudomonas cepacia CCT6659, Bacillus methylotrophicus UCP 1616 and Bacillus cereus UCP 1615) cultivated in mineral medium containing different carbon (glucose, sucrose, molasses and waste frying oil) and nitrogen [NH4NO3, (NH4)2SO4, peptone, yeast extract and corn steep liquor] sources. B. cereus stood out as the best biosurfactant producer when inoculated with a 1.5% cell suspension and cultivated at 28 °C and 200 rpm in 2.0% molasses and 1.0% corn steep liquor for 48 h. Under these conditions, medium surface tension was reduced to 26.2 ± 0.2 mN/m, and biosurfactant concentration achieved 2.05 ± 0.32 g/L. The biosurfactant showed a critical micelle concentration of 0.90 ± 0.05 g/L, proved to be highly stable in wide ranges of pH, salt concentration and heating temperature, and exerted low toxicity to larvae of Artemia salina as a marine environmental bioindicator. Structural characterisation of biosurfactant suggested a lipopeptide composition. The biotensioactive agent was shown to effectively remove motor oil adsorbed to marine rock (91.0 ± 0.4%) and to disperse it in seawater (70.0 ± 0.4%). The biosurfactant formulated with 0.2% potassium sorbate demonstrated considerable potential for application in the petroleum industry, where it could be successfully used as a commercial product to mobilize oil in marine environments.

Analytic prediction of histotripsy-induced bubble growth in an elastic medium

Histotripsy is a form of therapeutic ultrasound that liquefies tissue mechanically via acoustic cavitation. Bubble growth due to histotripsy excitation has been calculated analytically with high accuracy in a fluid medium. Tissue elasticity is a determining factor in the therapeutic efficacy of histotripsy, and has not been considered in analytic bubble dynamics calculations. In this study, an analytic model to predict histotripsy-induced bubble expansion based on the medium surface tension, viscosity, and inertia was extended to include the effects of medium stiffness. Good agreement was observed between the predictions of the model and numerical computations. The predictions of the model were also consistent with experimental observation of bubble expansion, though are dependent on the elasticity form. Bubble growth was weakly dependent on the medium elasticity for highly nonlinear, shock scattering histotripsy pulses, but was strongly dependent for purely tensile, microtripsy pulses. For both forms of histotripsy, bubble growth was completely suppressed when the elastic modulus exceeded 20 MPa and the peak negative pressures was less than 50 MPa. These results highlight the importance of the histotripsy insonation scheme on bubble growth in an elastic medium, as well the range of tissue elasticities for efficacious bubble-induced liquefaction.

Characterization of biosurfactants produced by the oil-degrading bacterium Rhodococcus erythropolis S67 at low temperature.

Production of trehalolipid biosurfactants by Rhodococcus erythropolis S67 depending on the growth temperature was studied. R. erythropolis S67 produced glycolipid biosurfactants such as 2,3,4-succinoyl-octanoyl-decanoyl-2'-decanoyl trehalose and 2,3,4-succinoyl-dioctanoyl-2'-decanoyl trehalose during the growth in n-hexadecane medium at 26 and 10°C, despite the different aggregate state of the hydrophobic substrate at low temperature. The surface tension of culture medium was found being reduced from 72 to 27 and 45mNm-1, respectively. Production of trehalolipid biosurfactants by R. erythropolis S67 at low temperature could be useful for the biodegradation of petroleum hydrocarbons at low temperatures by enhancing the bioremediation performance in cold regions.

Isolation of nitrate-reducing bacteria from an offshore reservoir and the associated biosurfactant production.

Biosurfactant producing nitrate-reducing bacteria (NRB) in anaerobic reservoir environments are closely associated with souring (H2S) control in the offshore oil and gas industry. Five NRB strains were screened from offshore produced water samples and all were identified as Pseudomonas stutzeri. Their biosurfactant producing abilities when fed on either glucose or glycerol media were investigated. P. stutzeri CX3 reduced the medium surface tension to 33.5 and 29.6 mN m−1, respectively, while growing on glucose or glycerol media. The CX3 strain was further inoculated to examine its growth performance, resulting in 32.4% and 94.5% of nitrate consumption over 228 hours of monitoring in two media, respectively. The composition analysis of the biosurfactant product generated by P. stutzeri CX3 was conducted through thin-layer chromatography, gas chromatography with a flame ionization detector (FID) and Fourier transform infrared spectroscopy (FT-IR). The biosurfactant product was identified as a mixture of a small part of lipopeptides and a large part of glycolipids while its critical micellar concentration (CMC) was as low as 35 mg L−1. The biosurfactant product demonstrated high stability over a wide range of temperature (4–121 °C), pH (2–10), and salinity (0–20% w/v) concentration. The results provided valuable technical and methodological support for effective offshore reservoir souring control and associated enhanced oil recovery activities.

Hydrocarbonoclastic Alcanivorax Isolates Exhibit Different Physiological and Expression Responses to n-dodecane.

Autochthonous microorganisms inhabiting hydrocarbon polluted marine environments play a fundamental role in natural attenuation and constitute promising resources for bioremediation approaches. Alcanivorax spp. members are ubiquitous in contaminated surface waters and are the first to flourish on a wide range of alkanes after an oil-spill. Following oil contamination, a transient community of different Alcanivorax spp. develop, but whether they use a similar physiological, cellular and transcriptomic response to hydrocarbon substrates is unknown. In order to identify which cellular mechanisms are implicated in alkane degradation, we investigated the response of two isolates belonging to different Alcanivorax species, A. dieselolei KS 293 and A. borkumensis SK2 growing on n-dodecane (C12) or on pyruvate. Both strains were equally able to grow on C12 but they activated different strategies to exploit it as carbon and energy source. The membrane morphology and hydrophobicity of SK2 changed remarkably, from neat and hydrophilic on pyruvate to indented and hydrophobic on C12, while no changes were observed in KS 293. In addition, SK2 accumulated a massive amount of intracellular grains when growing on pyruvate, which might constitute a carbon reservoir. Furthermore, SK2 significantly decreased medium surface tension with respect to KS 293 when growing on C12, as a putative result of higher production of biosurfactants. The transcriptomic responses of the two isolates were also highly different. KS 293 changes were relatively balanced when growing on C12 with respect to pyruvate, giving almost the same amount of upregulated (28%), downregulated (37%) and equally regulated (36%) genes, while SK2 transcription was upregulated for most of the genes (81%) when growing on pyruvate when compared to C12. While both strains, having similar genomic background in genes related to hydrocarbon metabolism, retained the same capability to grow on C12, they nevertheless presented very different physiological, cellular and transcriptomic landscapes.

Degradation of Polycyclic Aromatic Hydrocarbon Pyrene by Biosurfactant-Producing Bacteria Gordonia cholesterolivorans AMP 10

<p>Pyrene degradation and biosurfactant activity by a new strain identified as <em>Gordonia cholesterolivorans </em>AMP 10 were studied. The strain grew well and produced effective biosurfactants in the presence of glucose, sucrose, and crude oil. The biosurfactants production was detected by the decreased surface tension of the medium and emulsification activity. Analysis of microbial growth parameters showed that AMP10 grew best at 50 µg mL<sup>-1</sup> pyrene concentration, leading to 96 % degradation of pyrene within 7 days. The result of nested PCR analysis revealed that this isolate possessed the <em>nah</em>Ac gene which encodes dioxygenase enzyme for initial degradation of Polycyclic Aromatic Hydrocarbon (PAH). Observation of both tensio-active and emulsifying activities indicated that biosurfactants which produced by AMP 10 when grown on glucose could lower the surface tension of medium from 71.3 mN/m to 24.7 mN/m and formed a stable emulsion in used lubricant oil with an emulsifying index (E24) of 74%. According to the results, it is suggested that the bacterial isolates <em>G. cholesterolivorans</em> AMP10 are suitable candidates for bioremediation of PAH-contaminated environments.</p><p><strong>How to Cite</strong></p><p>Kurniati, T. H., Rusmana, I. Suryani, A. & Mubarik, N. R. (2016). Degradation of Polycyclic Aromatic Hydrocarbon Pyrene by Biosurfactant-Producing Bacteria <em>Gordonia cholesterolivorans</em> AMP 10. <em>Biosaintifika: Journal of Biology & Biology Education</em>, 8(3), 336-343. </p>

Downscaling the in vitro test of fungal bioremediation of polycyclic aromatic hydrocarbons: methodological approach.

The miniaturization and optimization of a white rot fungal bioremediation experiment is described in this paper. The optimized procedure allows determination of the degradation kinetics of anthracene. The miniaturized procedure requires only 2.5 ml of culture medium. The experiment is more precise, robust, and better controlled comparing it to classical tests in flasks. Using this technique, different parts, i.e., the culture medium, the fungi, and the cotton seal, can be analyzed. A simple sample preparation speeds up the analytical process. Experiments performed show degradation of anthracene up to approximately 60% by Irpex lacteus and up to approximately 40% by Pleurotus ostreatus in 25 days. Bioremediation of anthracene by the consortium of I. lacteus and P. ostreatus shows the biodegradation of anthracene up to approximately 56% in 23 days. At the end of the experiment, the surface tension of culture medium decreased comparing it to the blank, indicating generation of surfactant compounds.

Biological surface-active compounds from marine bacteria

ABSTRACTSurface-active compounds (SACs) are widely used in different industries as well as in many daily consumption products. However, with the increasing concern for their environmental acceptability, attention has turned towards biological SACs which are biodegradable, less toxic and more environmentally friendly. In this work, 176 marine hydrocarbon-degrading bacterial isolates from petroleum-contaminated sites along the Norwegian coastline were isolated and screened for their capacity to produce biological SACs. Among them, 18 isolates were capable of reducing the surface tension of the culture medium by at least 20 mN m−1 and/or capable of maintaining more than 40% of the emulsion volume after 24 h when growing on glucose or kerosene as carbon and energy source. These isolates were members of the genera Pseudomonas, Pseudoalteromonas, Rhodococcus, Catenovulum, Cobetia, Glaciecola, Serratia, Marinomonas and Psychromonas. Two isolates, Rhodococcus sp. LF-13 and Rhodococcus sp. LF-22, reduced surface tension of culture medium by more than 40 mN m−1 when growing on kerosene, n-hexadecane or rapeseed oil. The biosurfactants were produced by resting cells of the two Rhodococcus strains suggesting the biosynthesis of the biosurfactants was not necessarily associated with their growth on hydrocarbons.