Lipophilic compounds in biotechnology--interactions with cells and technological problems

A Rare Mono-Rhamnolipid Congener Efficiently Produced by Recombinant Pseudomonas aeruginosa YM4 via the Expression of Global Transcriptional Regulator irrE

Rhamnolipids (RLs) are widely used biosurfactants produced mainly by Pseudomonas aeruginosa and Burkholderia spp. in the form of mixtures of diverse congeners. The global transcriptional regulator gene irrE from radiation-tolerant extremophiles has been widely used as a stress-resistant element to construct robust producer strains and improve their production performance. A PrhlA-irrE cassette was constructed to express irrE genes in the Pseudomonas aeruginosa YM4 of the rhamnolipids producer strain. We found that the expression of irrE of Deinococcus radiodurans in the YM4 strain not only enhanced rhamnolipid production and the strain's tolerance to environmental stresses, but also changed the composition of the rhamnolipid products. The synthesized rhamnolipids reached a maximum titer of 26 g/L, about 17.9% higher than the original, at 48 h. The rhamnolipid production of the recombinant strain was determined to be mono-rhamnolipids congener Rha-C10-C12, accounting for 94.1% of total products. The critical micelle concentration (CMC) value of the Rha-C10-C12 products was 62.5 mg/L and the air-water surface tension decreased to 25.5 mN/m. The Rha-C10-C12 products showed better emulsifying activity on diesel oil than the original products. This is the first report on the efficient production of the rare mono-rhamnolipids congener Rha-C10-C12 and the first report that the global regulator irrE can change the components of rhamnolipid products in Pseudomonas aeruginosa.

Evidence for enhanced dissipation of chlorpyrifos in an agricultural soil inoculated with Serratia rubidaea strain ABS 10

The insecticide ¹⁴C-chlorpyrifos was found mineralized in a Tunisian soil with repeated exposure to it. From this soil, a bacterial strain was isolated that was able to grow in a minimal salt medium (MSM) supplemented with 25 mg L^-1 of chlorpyrifos. It was characterized as Serratia rubidaea strain ABS 10 using morphological and biochemical analyses, as well as 16S rRNA sequencing. In a liquid culture, the S. rubidaea strain ABS 10 was able to dissipate chlorpyrifos almost entirely within 48 h of incubation. Although the S. rubidaea strain ABS 10 was able to grow in an MSM supplemented with chlorpyrifos and dissipate it in a liquid culture, it was not able to mineralize ¹⁴C-chlorpyrifos. Therefore, it can be concluded that the dissipation capability of this bacteria might be attributed to its capacity to adsorb CHL. It can also be ascribed to other reasons such as the formation of biogenic non-extractable residues. In both non-sterile and sterile soil inoculated with S. rubidaea strain ABS 10, chlorpyrifos was more rapidly dissipated than in controls with DT₅₀ of 1.38 and 1.05 days, respectively.

Galleria mellonella for systemic assessment of anti-Candida auris using amphotericin B loaded in nanoemulsion

Galleria mellonella is a model that uses adult larvae to assess the prophylactic, therapeutic, and acute toxic potential of substances. Given their benefits, G. mellonella models are being employed in investigations of systemic infections caused by highly resistant microorganisms. Among the multiresistant microorganisms, we highlight Candida auris, a yeast with high mortality potential and resistance. Among the potential drugs, amphotericin B (AmB) stands out; however, microbial resistance episodes and side effects caused by low selectivity have been observed. The incorporation of AmB into a nanoemulsion (NE) can contribute to the control of C. auris infections and resistance as well as decrease the side effects of this drug. This study aimed to develop AmB-loaded NE (NEA) and evaluate its antifungal action against C. auris in G. mellonella. NEs were obtained by using sunflower oil and cholesterol as the oily phase, polyoxyethylene 20 cetyl ether (Brij® 58) and soy phosphatidylcholine as the surfactant system, and PBS buffer as the aqueous phase. An alternative in vivo assay with G. mellonella for acute toxicity and infection was performed using adult stage larvae (200 mg to 400 mg). According to the obtained results, NE and NEA exhibited sizes of 43 and 48 nm, respectively. The PDI was 0.285 and 0.389 for NE and NEA, respectively. The ZP showed electronegativity for both systems, with -3.77 mV and -3.80 mV for NE and NEA, respectively. Acute toxicity showed that free AmB had greater acute toxicity potential than NEA. The survival assay showed high larval viability. NEA had a better antifungal profile against systemic infection in G. mellonella. It is concluded that the alternative model proved to be an efficient in vivo assay to determine the toxicity and evaluate the therapeutic property of free AmB and NEA in systemic infections caused by C. auris.

Isopropanol biodegradation by immobilized Paracoccus denitrificans in a three-phase fluidized bed reactor

A three-phase bed bioreactor including a mix of immobilized microbes was used to degrade isopropanol (IPA). The immobilization method was studied and cells immobilized with calcium alginate, polyvinyl alcohol, activated carbon, and SiO₂ were demonstrated to be the best immobilization method for the degradation of 90% of 2 g/L IPA in just 4 days, 1 day earlier than with free cells. Acetone was monitored as an indicator of microbial IPA utilization as the major intermediate of aerobic IPA biodegradation. The bioreactor was operated at hydraulic retention time (HRT) values of 32, 24, 16, 12, and 10 hr, which correspond to membrane fluxes of 0.03, 0.04, 0.06, 0.08, and 0.10 L/m²/hr, respectively. The chemical oxygen demand (COD) removal efficiencies were maintained at 98.0, 97.8, 89.1, 80.6, and 71.1% at a HRT of 32, 24, 16, 12, and 10 hr, respectively, while the IPA degradations were 98.6, 98.3, 90.3, 81.6, and 73.3%, respectively. With a comprehensive consideration of COD removal and economy, the optimal HRT was 24 hr. The results demonstrate the potential of immobilized mixed bacterial consortium in a three-phase fluidized bed reactor system for the aerobic treatment of wastewater containing IPA.

Enantiorecognition of planar "metallocenic" chirality by a nitrile hydratase/amidase bienzymatic system

For the first time, a bacterial strain expressing a nitrile hydratase/amidase activity was able to recognize a planar element of chirality: Rhodococcus rhodochrous PA-34 whole cells catalysed with a high level of enantioselectivity the biotransformation of a novel nitrile ferrocene derivative into its corresponding amide and/or acid. An important parameter in the enzymatic recognition is the choice of the inducer selected for the bacterial growth phase.

Statistical optimization of culture medium for production of exopolysaccharide from endophytic fungus Bionectria ochroleuca and its antitumor effect in vitro

Endophytic fungi have been recognized as possible useful sources of bioactive metabolites. However, exopolysaccharide (EPS) production from endophytic fungi and its antitumor activity have been less explored. In the present study, endophtic fungus Bionectria ochroleuca M21 was exploited for the production of EPS in submerged culture. Among tested medium components, glucose, yeast extract, MgSO₄ and Tween80 were found to be effective and significant on EPS production. Response surface methodology (RSM) was employed to optimize medium composition. The results showed that the significant factors were glucose, yeast extract and Tween80. The optimal medium was observed at the composition of glucose 55.7 g/L, yeast extract 6.04 g/L, MgSO₄ 0.25g/L and Tween80 0.1 % (v/v). Using the optimized medium, EPS production was achieve at 2.65 ± 0.16 g/L after 4 days fermentation in a 5L bioreactor. Examination of cytotoxicity showed that the EPS from B. ochroleuca M21 did not have cytotoxic activity on human liver HL-7702 cells at concentration 0.025-1.6 mg/mL. In contrast, the EPS exhibited antiproliferative activities against cell lines of liver cancer (HepG2), gastric cancer (SGC-7901) and colon cancer (HT29) in a dose- and time-dependent manner in the concentration ranges of 0.1-0.45 mg/mL.

Biosurfactant produced from Actinomycetes nocardiopsis A17: Characterization and its biological evaluation

This investigation aims to isolate an Actinomycetes strain producing a biosurfactant from the unexplored region of industrial and coal mine areas. Actinomycetes are selected for this study as their novel chemistry was not exhausted and they have tremendous potential to produce bioactive secondary metabolites. The biosurfactant was characterized and further needed to be utilized for pharmaceutical dosage form. Isolation, purification, screening, and characterization of the Actinomycetes A17 were done followed by its fermentation in optimized conditions. The cell-free supernatant was used for the extraction of the biosurfactant and precipitated by cold acetone. The dried precipitate was purified by TLC and the emulsification index, surface tension and CMC were determined. The isolated strain with preferred results was identified as Actinomycetes nocardiopsis A17 with high foam-forming properties. It gives lipase, amylase, gelatinase, and protease activity. The emulsification index was found to be 93±0.8 with surface tension 66.67 dyne/cm at the lowest concentration and cmc 0.6 μg/ml. These biosurfactants were characterized by Fourier transform infra red (FT-IR) spectroscopy and liquid chromatography-mass spectrometry (LC-MS). Therefore, it can be concluded that the biosurfactant produced by Actinomycetes nocardiopsis sp. strain A17 was found to have satisfactory results with high surface activity and emulsion-forming ability.

Enhanced biotransformation of dehydroepiandrosterone to 3β,7α,15α-trihydroxy-5-androsten-17-one with Gibberella intermedia CA3-1 by natural oils addition

Dihydroxylation of dehydroepiandrosterone (DHEA) is an essential step in the synthesis of many important pharmaceutical intermediates. However, the solution to the problem of low biohydroxylation conversion in the biotransformation of DHEA has yet to be found. The effects of natural oils on the course of dihydroxylation of DHEA to 3β,7α,15α-trihydroxy-5-androsten-17-one (7α,15α-diOH-DHEA) were studied. With rapeseed oil (2 %, v/v) addition, the bioconversion efficiency was improved, and the 7α,15α-diOH-DHEA yield was increased by 40.8 % compared with that of the control at DHEA concentration of 8.0 g/L. Meantime, the ratio of 7α,15α-diOH-DHEA to 7α-OH-DHEA was also increased by 4.5 times in the rapeseed oil-containing system. To explain the mechanism underlying the increase of 7α,15α-diOH-DHEA yield, the effects of rapeseed oil on the pH of the bioconversion system, the cell growth and integrity of Gibberella intermedia CA3-1, as well as the membrane composition were systematically studied. The addition of rapeseed oil enhanced the substrate dispersion and maintained the pH of the system during bioconversion. Cells grew better with favorable integrity. The fatty acid profile of G. intermedia cells revealed that rapeseed oil changed the cell membrane composition and improved cell membrane permeability for lipophilic substrates.

The influence of bioaugmentation and biosurfactant addition on bioremediation efficiency of diesel-oil contaminated soil: feasibility during field studies

The study focused on assessing the influence of bioaugmentation and addition of rhamnolipids on diesel oil biodegradation efficiency during field studies. Initial laboratory studies (measurement of emitted CO2 and dehydrogenase activity) were carried out in order to select the consortium for bioaugmentation as well as to evaluate the most appropriate concentration of rhamnolipids. The selected consortium consisted of following bacterial taxa: Aeromonas hydrophila, Alcaligenes xylosoxidans, Gordonia sp., Pseudomonas fluorescens, Pseudomonas putida, Rhodococcus equi, Stenotrophomonas maltophilia, Xanthomonas sp. It was established that the application of rhamnolipids at 150 mg/kg of soil was most appropriate in terms of dehydrogenase activity. Based on the obtained results, four treatment methods were designed and tested during 365 days of field studies: I) natural attenuation; II) addition of rhamnolipids; III) bioaugmentation; IV) bioaugmentation and addition of rhamnolipids. It was observed that bioaugmentation contributed to the highest diesel oil biodegradation efficiency, whereas the addition of rhamnolipids did not notably influence the treatment process.

Lipophilic organic pollutants induce changes in phospholipid and membrane protein composition leading to Vero cell morphological change

Membrane damage related to morphological change in Vero cells is a sensitive index of the composite biotoxicity of trace lipophilic chemicals. However, judging whether the morphological change in Vero cells happens and its ratio are difficult because it is not a quantitative characteristic. To find biomarkers of cell morphological change for quantitatively representing the ratio of morphological changed cell, the mechanism of cell membrane damage driven by typical lipophilic chemicals, such as trichlorophenol (TCP) and perfluorooctanesulphonate (PFOS), was explored. The ratio of morphologically changed cells generally increased with increased TCP or PFOS concentrations, and the level of four major components of phospholipids varied with concentrations of TCP or PFOS, but only the ratio of phosphatidylcholine (PC)/phosphatidylethanolamine (PE) decreased regularly as TCP or PFOS concentrations increased. Analysis of membrane proteins showed that the level of vimentin in normal cell membranes is high, while it decreases or vanishes after TCP exposure. These variations in phospholipid and membrane protein components may result in membrane leakage and variation in rigid structure, which leads to changes in cell morphology. Therefore, the ratio of PC/PE and amount of vimentin may be potential biomarkers for representing the ratio of morphological changed Vero cell introduced by trace lipophilic compounds, thus their composite bio-toxicity.

Influence of rutin, FeSO4, Tween 80, aspartate and complex vitamins on synthesis of fungal exopolysaccharide

The influence of several components on exopolysaccharide (EPS) production and antioxidative activity (TEAC, Trolox-Equivalent Antioxidant Capacity) as well as their effects on the morphological development and cell viability of Phellinus sp. P0988 was determined. Rutin, FeSO(4), Tween 80 and complex vitamins were found to impose a stronger influence on EPS production and TEAC compared to their effects on the mycelia growth of Phellinus sp. P0988. The relative effects of these components on EPS activity were found to be different from that on EPS yield. Rutin and aspartate significantly affected EPS TEAC (P<0.05), while FeSO(4) and Tween 80 significantly influenced EPS production (P<0.05). These results yielded the optimum culture medium composition, with an EPS yield and TEAC of 6.2±0.2 g/L and 5.5±0.1 mM, respectively.

Effects of Tween 80 and pH on mycelial pellets and exopolysaccharide production in liquid culture of a medicinal fungus

This study investigated the effects of surfactant additives and medium pH on mycelial morphology and exopolysaccharide (EPS) production in liquid culture of a valuable medicinal fungus Cordyceps sinensis Cs-HK1. In the medium containing 20 g l−1 glucose and 6 g l−1 peptone as the sole nitrogen source, the Cs-HK1 fungal mycelia formed smooth and spherical pellets about 1.8-mm mean diameter. The mycelial pellets became less uniform at pH (4.0–5.0) lower than the optimum (pH 6.0) or turned to filamentous form at higher pH (8–9). Surfactants added to the medium inhibited pellet formation, resulting in smaller and looser pellets. Tween 80 exhibited a remarkable promoting effect on EPS production, increasing the EPS yield more than twofold at 1.5% (w/v), which was most probably attributed to the stimulation of EPS biosynthesis and release from the fungal cells by Tween 80.

Utilization of Triton X-100 and polyethylene glycols during surfactant-mediated biodegradation of diesel fuel

The hypothesis regarding preferential biodegradation of surfactants applied for enhancement of microbial hydrocarbons degradation was studied. At first the microbial degradation of sole Triton X-100 by soil isolated hydrocarbon degrading bacterial consortium was confirmed under both full and limited aeration with nitrate as an electron acceptor. Triton X-100 (600 mg/l) was utilized twice as fast for aerobic conditions (t(1/2)=10.3h), compared to anaerobic conditions (t(1/2)=21.8h). HPLC/ESI-MS analysis revealed the preferential biodegradation trends in both components classes of commercial Triton X-100 (alkylphenol ethoxylates) as well as polyethylene glycols. The obtained results suggest that the observed changes in the degree of ethoxylation for polyethylene glycol homologues occurred as a consequence of the 'central fission' mechanism during Triton X-100 biodegradation. Subsequent experiments with Triton X-100 at approx. CMC concentration (150 mg/l) and diesel oil supported our initial hypothesis that the surfactant would become the preferred carbon source even for hydrocarbon degrading bacteria. Regardless of aeration regimes Triton X-100 was utilized within 48-72 h. Efficiency of diesel oil degradation was decreased in the presence of surfactant for aerobic conditions by approx. 25% reaching 60 instead of 80% noted for experiments without surfactant. No surfactant influence was observed for anaerobic conditions.

Propidium iodide staining method for testing the cytotoxicity of 2,4,6-trichlorophenol and perfluorooctane sulfonate at low concentrations with Vero cells

In this article, the feasibility of propidium iodide (PI) staining based on cell membrane damage as a sensitive and quantitative method to test the cytotoxicity of typical lipophilic compounds including 2,4,6-trichlorophenol (TCP) and perfluorooctane sulfonate (PFOS) was examined. The sensitivity of PI staining was compared to that of the methylthiazol-2-yl-2,5-diphenyl tetrazolium bromide (MTT) assay. We found a good correlation between PI uptake and increasing concentrations of TCP (10-50 μM) and PFOS (20-50 μM) at lower concentrations than those between growth inhibition ratio determined by the MTT assay and increasing concentrations of TCP (150-400 μM) and PFOS (100-500 μM). These findings indicated that the PI staining was more sensitive than the MTT assay. Furthermore, both the amount of PI uptake and the ratio of morphologically changed cells increased with increasing TCP concentrations, suggesting that PI staining may be a suitable quantitative substitute for the original method based on the observation of morphological changes in Vero cells. Our data also suggest that it is possible that the cell membrane damage that resulted in increased PI uptake may be due to variations in the phospholipid and protein content of the membrane, which are affected by interactions between the lipophilic compounds and components of the cell membrane.

Emulsification potential of a newly isolated biosurfactant-producing bacterium, Rhodococcus sp. strain TA6

An indigenous biosurfactant producing bacterium, Rhodococcus sp. strain TA6 was isolated from Iranian oil contaminated soil using an efficient enrichment and screening method. During growth on sucrose and several hydrocarbon substrates as sole carbon source, the bacterium could produce biosurfactants. As a result of biosurfactant synthesis, the surface tension of the growth medium was reduced from 68mNm(-1) to values below 30mNm(-1). The biosurfactant was capable of forming stable emulsions with various hydrocarbons ranging from pentane to light motor oil. Preliminary chemical characterization revealed that the TA6 biosurfactant consisted of extracellular lipids and glycolipids. The biosurfactant was stable during exposure to high salinity (10% NaCl), elevated temperatures (120°C for 15min) and within a wide pH range (4.0-10.0). The culture broth was effective in recovering up to 70% of the residual oil from oil-saturated sand packs which indicates the potential value of the biosurfactant in enhanced oil recovery.

Biomedical and therapeutic applications of biosurfactants

During the last years, several applications of biosurfactants with medical purposes have been reported. Biosurfactants are considered relevant molecules for applications in combating many diseases and as therapeutic agents due to their antibacterial, antifungal and antiviral activities. Furthermore, their role as anti-adhesive agents against several pathogens illustrate their utility as suitable anti-adhesive coating agents for medical insertional materials leading to a reduction of a large number of hospital infections without the use of synthetic drugs and chemicals. Biomedical and therapeutic perspectives of biosurfactants applications are presented and discussed in this chapter.

Androstenedione production by biotransformation of phytosterols

Androstenedione is a key intermediate of microbial steroid metabolism. It belongs to the 17-keto steroid family and is used as starting material for the preparation of different steroids. Androstenedione can be produced by microbial side chain cleavage of phytosterol, which is an alternative to multi-step chemical synthesis. In this review, various methods of biotransformation of sterols to androstenedione are surveyed. It begins with the history and current research status in this field. The existing methods of chemical and biochemical synthesis are examined. Various issues related to these methods and how researchers have addressed them is presented. Among these, the low solubility of sterols in aqueous systems is a critical problem since it limits the product yield. The main content of this review focuses on new methods of biotransformation that are being investigated. Recent biotechnological advances in this field are presented. The review ends with a note on future perspectives.

MICROALGAL BIOTRANSFORMATION OF STEROIDS(1)

Microbial biotransformation of steroids is not a new concept, but most studies in this field have focused on fungal and bacterial systems. Microalgae, despite their photosynthetic ability and immense biodiversity, have not received much attention in this aspect until recently. Since the publication of the first article on microalgal biotransformation of steroids about 20 years ago, there have been many reports describing different modifications, including hydroxylation, reduction, side-chain degradation, and isomerization introduced by these microorganisms on estrane, androstane, and pregnane derivatives. On the other hand, the development of new large-scale cultivation systems, the adaptation of existing fermentation techniques to microalgae, and the introduction of microalgal genetic manipulation methods have made these organisms promising candidates for a wide range of biotechnological processes, including biotransformations. In this review, we have summarized the steroid transformation patterns of several microalgal strains and present a perspective of the future trends in microalgal biotechnology, including the possibility of adapting relatively new techniques, such as organic media catalysis and cell immobilization, to this specific field.

Isolation and partial characterization of a biosurfactant produced by Streptococcus thermophilus A

Isolation and characterization of the surface active components from the crude biosurfactant produced by Streptococcus thermophilus A was studied. A fraction rich in glycolipids was obtained by the fractionation of crude biosurfactant using hydrophobic interaction chromatography. Molecular (by Fourier transform infrared spectroscopy) and elemental compositions (by X-ray photoelectron spectroscopy) were determined. Critical micelle concentration achieved was 20 g/l, allowing for a surface tension value of 36 mJ/m(2). Moreover, this glycolipid rich fraction was found to be an anti-adhesive and antimicrobial agent against several bacterial and yeast strains isolated from explanted voice prostheses. Further purification steps should be carefully analyzed as each purification step will increase the costs and decreases the amounts of biosurfactants recovered.

Bioconversion of isopropanol by a solvent tolerant Sphingobacterium mizutae strain

The bioconversion of high concentration isopropanol (2-propanol, IPA) was investigated by a solvent tolerant strain of bacteria, which was identified as Sphingobacterium mizutae ST2 by partial 16S rDNA gene sequencing. This strain of bacteria exhibited the ability to utilise high concentration isopropanol as the sole carbon source, with mineralization occurring via an acetone intermediate into central metabolism. The biodegradative performance of this strain for IPA was examined over a 2-38 g l(-1) concentration range, using specific growth rate (mu) and conversion rate analysis. Maximum specific growth rates (mu(max)) of 0.0045 h(-1 )were routinely obtainable on IPA. In addition, the highest specific IPA degradation rate was obtained at a concentration of 7.5 g l(-1) with a corresponding value of 0.045 g IPA g cells(-1) h(-1). While the highest acetone yield reached its maximum value of 0.940 g acetone g IPA(-1) at 7.5 g IPA l(-1). This is the first report on bioconversion of isopropanol at such high concentration by this solvent tolerant strain of S. mizutae and may allow its application in novel biocatalytic processes for effective biological conversion in two-phase solvent systems.

Display of a thermostable lipase on the surface of a solvent-resistant bacterium, Pseudomonas putida GM730, and its applications in whole-cell biocatalysis

Background

Whole-cell biocatalysis in organic solvents has been widely applied to industrial bioprocesses. In two-phase water-solvent processes, substrate conversion yields and volumetric productivities can be limited by the toxicity of solvents to host cells and by the low mass transfer rates of the substrates from the solvent phase to the whole-cell biocatalysts in water.

Results

To solve the problem of solvent toxicity, we immobilized a thermostable lipase (TliA) from Pseudomonas fluorescens on the cell surface of a solvent-resistant bacterium, Pseudomonas putida GM730. Surface immobilization of enzymes eliminates the mass-transfer limitation imposed by the cell wall and membranes. TliA was successfully immobilized on the surface of P. putida cells using the ice-nucleation protein (INP) anchoring motif from Pseudomonas syrinage. The surface location was confirmed by flow cytometry, protease accessibility and whole-cell enzyme activity using a membrane-impermeable substrate. Three hundred and fifty units of whole-cell hydrolytic activity per gram dry cell mass were obtained when the enzyme was immobilized with a shorter INP anchoring motif (INPNC). The surface-immobilized TliA retained full enzyme activity in a two-phase water-isooctane reaction system after incubation at 37°C for 12 h, while the activity of the free form enzyme decreased to 65% of its initial value. Whole cells presenting immobilized TliA were shown to catalyze three representative lipase reactions: hydrolysis of olive oil, synthesis of triacylglycerol and chiral resolution.

Conclusion

In vivo surface immobilization of enzymes on solvent-resistant bacteria was demonstrated, and appears to be useful for a variety of whole-cell bioconversions in the presence of organic solvents.

Physicochemical and functional characterization of a biosurfactant produced by Lactococcus lactis 53

Isolation and identification of key components of the crude biosurfactant produced by Lactococcus lactis 53 was studied. Fractionation was achieved by hydrophobic interaction chromatography which allowed the isolation of a fraction rich in glycoproteins. Molecular (by Fourier transform infrared spectroscopy) and elemental compositions (by X-ray photoelectron spectroscopy) were determined. Critical micelle concentration achieved for the isolated fraction was 14 g/l, allowing for a surface tension value of 36 mJ/m(2). Moreover, the isolated fraction, stable to pH changes between 5 and 9, was found to be an anti-adhesive and antimicrobial agent against several bacterial and yeast strains isolated from explanted voice prostheses, even at low concentrations. Further purification steps should be carefully analyzed as each purification step will increase the costs and decreases the amounts of biosurfactants recovered.

Biosurfactants: potential applications in medicine

The use and potential commercial application of biosurfactants in the medical field has increased during the past decade. Their antibacterial, antifungal and antiviral activities make them relevant molecules for applications in combating many diseases and as therapeutic agents. In addition, their role as anti-adhesive agents against several pathogens indicates their utility as suitable anti-adhesive coating agents for medical insertional materials leading to a reduction in a large number of hospital infections without the use of synthetic drugs and chemicals. This review looks at medicinal and therapeutic perspectives on biosurfactant applications.

Concurrent corticosteroid and phenanthrene transformation by filamentous fungus Cunninghamella elegans

A filamentous fungus Cunninghamella elegans IM 1785/21Gp which displays ability of 17alpha,21-dihydroxy-4-pregnene-3,20-dione (cortexolone) 11-hydroxylation (yielding epihydrocortisone (eF) and hydrocortisone (F)) and polycyclic aromatic hydrocarbons (PAHs) degradation, was used as a microbial eucaryotic model to study the relationships between mammalian steroid hydroxylation and PAHs metabolization. The obtained results showed faster transformation of phenanthrene in Sabouraud medium supplemented with steroid substrate (cortexolone). Simultaneously phenanthrene stimulated epihydrocortisone production from cortexolone. In phenanthrene presence the ratio between cortexolone hydroxylation products (hydrocortisone and epihydrocortisone) was changed from 1:5.1-6.2 to 1:7.6-8.4 in the culture without phenanthrene. Cytochrome P-450 content significantly increased after the culture supplementation by the second substrate, phenanthrene or cortexolone, adequately. To confirm the involvement of cytochrome P-450 in phenanthrene metabolism, the inhibition studies were performed. The cytochrome P-450 inhibitors SKF 525-A (1.5mM) and 2-methyl-1,2-di-3-pyridyl-1-propanone (metyrapone) (2mM) inhibited phenanthrene transformation by 80 and 62%, respectively. 1-aminobenzotriazole (1mM) completely blocked phenanthrene metabolism. The obtained results suggest a presence of connections between steroid hydroxylases and enzymes involved in PAH degradation in C. elegans.

Water-in-oil macroemulsions sustain long-term viability of microbial cells in organic solvents

Extremely stable water-in-oil macroemulsions have been obtained by dispersing water in isooctane in the presence of lecithin. Either prokaryotic (Escherichia coli) and eukaryotic (Saccharomyces cerevisiae and Rhodotorula minuta) cells hosted in these water-in-oil macroemulsions are viable for weeks despite the consistent excess of organic solvent (ranging from 70 to 84%, v/v) in these ternary systems. Conjugation occurs upon mixing macroemulsions containing F(+) or F(-) Escherichia coli strains, indicating consistent mass transfer between the water droplets. Populations of yeasts hosted in water-in-oil macroemulsion feature a higher frequency of cells aggregation when compared with the corresponding populations suspended in homogeneous aqueous media.