Alexander Dr. Shulga

Bio: Alexander Dr. Shulga is an academic researcher. The author has contributed to research in topics: Rhamnolipid & Bacillus subtilis. The author has an hindex of 3, co-authored 6 publications receiving 216 citations.

Rhamnolipid-biosurfactant permeabilizing effects on gram-positive and gram-negative bacterial strains.

Abstract: The potential of biosurfactant PS to permeabilize bacterial cells of Pseudomonas aeruginosa, Escherichia coli, and Bacillus subtilis on growing (in vivo) and resting (in vitro) cells was studied. Biosurfactant was shown to have a neutral or detrimental effect on the growth of Gram-positive strains, and this was dependent on the surfactant concentration. The growth of Gram-negative strains was not influenced by the presence of biosurfactant in the media. Cell permeabilization with biosurfactant PS was shown to be more effective with B. subtilis resting cells than with Pseudomonas aeruginosa. Scanning-electron microscopy observations showed that the biosurfactant PS did not exert a disruptive action on resting cells such that it was detrimental to the effect on growing cells of B. subtilis. Low critical micelle concentrations, tender action on nongrowing cells, and neutral effects on the growth of microbial strains at low surfactant concentrations make biosurfactant PS a potential candidate for application in different industrial fields, in environmental bioremediation, and in biomedicine.

Anti-herpesvirus activities of Pseudomonas sp. S-17 rhamnolipid and its complex with alginate

Abstract: The rhamnolipid biosurfactant PS-17 and its complex with the polysaccharide alginate, both produced by the Pseudomonas sp. S-17 strain, were studied for their antiviral activity against herpes simplex virus (HSV) types 1 and 2. They significantly inhibited the herpesvirus cytopathic effect (CPE) in the Madin-Darby bovine kidney (MDBK) cell line. The investigations were carried out according to the CPE inhibition assay protocol. The suppressive effect of the compounds on HSV replication was dose-dependent and occurred at concentrations lower than the critical micelle concentration of the surfactant. The 50% inhibitory concentration (IC50) of rhamnolipid PS-17 was 14.5 microg/ml against HSV-1 and 13 microg/ml against HSV-2. The IC50 values of the complex were 435 microg/ml for HSV-1 and 482 microg/ml for HSV-2. The inhibitory effects of the substances were confirmed by measuring the infectious virus yields with the multicycle virus growth experimental design as well: deltalog CCID50 of 1.84-2.0 against the two types of herpes simplex viruses by rhamnolipid PS-17 (20 microg/ml), and a strong reduction of the HSV-2 virus yield under the effect of the alginate complex at a concentration of 450 microg/ml. The results indicate that rhamnolipid PS-17 and its alginate complex may be considered as promising substances for the development of anti-herpetic compounds.

New rhamno-lipid-alginate polymer complexes

Abstract: Novel bacteria (A) of genus Pseudomonas, suitable for the production of rhamnolipid-alginate polymer complexes (I), are obtained by culturing a soil sample from the 'Borislav' oil-field (western Ukraine) in agar slant tubes or agar plates in a nutrient broth of composition (g/l): mannitol (20.0), CaCl2.2H2O (0.1), MgSO4.7H2O (0.4), cetyltrimethylammonium bromide (0.2), methylene blue (0.005), K2HPO4.2H2O (0.44), KH2PO4 (0.34), agar (15.0), trace salts (2 ml/l) FeSO4.7H2O, MnSO4.H2O (1.5) and (NH4)6Mo7O24 (0.6), with addition of 1.5% 'Bacto-Agar' (RTM) at pH 7.0. Also claimed are: (i) the recovery of (A) from the soil samples by culturing as above; (ii) a method for multiplication of (A) by preparing and sterilising an aqueous culture medium containing assimilable carbon and nitrogen sources, inoculating with (A) and carrying out agitated submerged aerobic culture at 20-35 deg C and pH 6.5-7.5; (iii) the preparation of (I) by culturing (A) as in (ii), separating the bacterial cells from the aqueous medium and optionally recovering (I) from the cell-free aqueous medium; (iv) novel (I) having an alginate component of formula (Alg) and rhamnolipid components of formula (RL I) and (RL II) (specifically where (I) comprises two components (RL I) and (RL II) and one (Alg) component); and (v) aqueous concentrates, emulsions or solutions containing the new (I) at 6.0-12.0 g/l, 0.05-5 wt.% or 0.1-15 wt.% respectively.

Rhamnolipid alginate polymer complex, microbiological process for its preparation, rhamnolipid alginate polymer complex preparations and their uses

Abstract: Rhamnolipid alginate polymer complex of building blocks of structures obtainable by a microbiological process with fermentation of a bacterium of the genus Pseudomonas capable of producing rhamnolipid-alginate polymer complexes, the process comprising the steps of - Produces an aqueous, at least one assimilable carbon source, at least one assimilable nitrogen source and known nutrient salts in suitable concentrations containing nutrient medium and this sterilized; - the nutrient medium thus obtained is inoculated with a bacterium of the genus Pseudomonas; - cultivating the bacterium of the genus Pseudomonas at a pH in the range of 6.5 to 7.5 and at a temperature in the range of 20 to 35 ° C aerobically in agitated submersed culture; - Separates the cells of the bacterium of the genus Pseudomonas in a conventional manner from the aqueous medium; and optionally - The rhamnolipid-alginate polymer complexes from the cell-free aqueous medium wins.

Rhamnolipid-Alginatpolymer-Komplex, mikrobiologisches Verfahren zu seiner Herstellung, Rhamnolipid-Alginatpolymer-Komplex-Zubereitungen und deren Verwendungen

Abstract: Rhamnolipid-Alginatpolymer-Komplex aus Bausteinen der Strukturen erhaltlich durch ein mikrobiologisches Verfahren unter Fermentation eines zur Erzeugung von Rhamnolipid-Alginatpolymer-Komplexen befahigten Bakteriums des Genus Pseudomonas, wobei das Verfahren die Schritte umfast, das man – ein wasriges, mindestens eine assimilierbare Kohlenstoffquelle, mindestens eine assimilierbare Stickstoffquelle und an sich bekannte Nahrsalze in geeigneten Konzentrationen enthaltendes Nahrmedium herstellt und dieses sterilisiert; – das so erhaltene Nahrmedium mit einem Bakterium des Genus Pseudomonas beimpft; – das Bakterium des Genus Pseudomonas bei einem pH-Wert im Bereich von 6,5 bis 7,5 und bei einer Temperatur im Bereich von 20 bis 35 °C aerob in bewegter Submerskultur zuchtet; – die Zellen des Bakteriums des Genus Pseudomonas auf an sich bekannte Weise von dem wasrigen Medium abtrennt; und gegebenenfalls – die Rhamnolipid-Alginatpolymer-Komplexe aus dem zellfreien wasrigen Medium gewinnt.

Microbial biosurfactants production, applications and future potential

Abstract: Microorganisms synthesise a wide range of surface-active compounds (SAC), generally called biosurfactants. These compounds are mainly classified according to their molecular weight, physico-chemical properties and mode of action. The low-molecular-weight SACs or biosurfactants reduce the surface tension at the air/water interfaces and the interfacial tension at oil/water interfaces, whereas the high-molecular-weight SACs, also called bioemulsifiers, are more effective in stabilising oil-in-water emulsions. Biosurfactants are attracting much interest due to their potential advantages over their synthetic counterparts in many fields spanning environmental, food, biomedical, and other industrial applications. Their large-scale application and production, however, are currently limited by the high cost of production and by limited understanding of their interactions with cells and with the abiotic environment. In this paper, we review the current knowledge and the latest advances in biosurfactant applications and the biotechnological strategies being developed for improving production processes and future potential.

Rhamnolipids: diversity of structures, microbial origins and roles

Abstract: Rhamnolipids are glycolipidic biosurfactants produced by various bacterial species. They were initially found as exoproducts of the opportunistic pathogen Pseudomonas aeruginosa and described as a mixture of four congeners: α-L-rhamnopyranosyl-α-L-rhamnopyranosyl-β-hydroxydecanoyl-β-hydroxydecanoate (Rha-Rha-C10-C10), α-L-rhamnopyranosyl-α-L-rhamnopyranosyl-β-hydroxydecanoate (Rha-Rha-C10), as well as their mono-rhamnolipid congeners Rha-C10-C10 and Rha-C10. The development of more sensitive analytical techniques has lead to the further discovery of a wide diversity of rhamnolipid congeners and homologues (about 60) that are produced at different concentrations by various Pseudomonas species and by bacteria belonging to other families, classes, or even phyla. For example, various Burkholderia species have been shown to produce rhamnolipids that have longer alkyl chains than those produced by P. aeruginosa. In P. aeruginosa, three genes, carried on two distinct operons, code for the enzymes responsible for the final steps of rhamnolipid synthesis: one operon carries the rhlAB genes and the other rhlC. Genes highly similar to rhlA, rhlB, and rhlC have also been found in various Burkholderia species but grouped within one putative operon, and they have been shown to be required for rhamnolipid production as well. The exact physiological function of these secondary metabolites is still unclear. Most identified activities are derived from the surface activity, wetting ability, detergency, and other amphipathic-related properties of these molecules. Indeed, rhamnolipids promote the uptake and biodegradation of poorly soluble substrates, act as immune modulators and virulence factors, have antimicrobial activities, and are involved in surface motility and in bacterial biofilm development.

Anti-adhesion activity of two biosurfactants produced by Bacillus spp. prevents biofilm formation of human bacterial pathogens.

Abstract: In this work, two biosurfactant-producing strains, Bacillus subtilis and Bacillus licheniformis, have been characterized Both strains were able to grow at high salinity conditions and produce biosurfactants up to 10% NaCl Both extracted-enriched biosurfactants showed good surface tension reduction of water, from 72 to 26–30 mN/m, low critical micelle concentration, and high resistance to pH and salinity The potential of the two lipopeptide biosurfactants at inhibiting biofilm adhesion of pathogenic bacteria was demonstrated by using the MBEC device The two biosurfactants showed interesting specific anti-adhesion activity being able to inhibit selectively biofilm formation of two pathogenic strains In particular, Escherichia coli CFT073 and Staphylococcus aureus ATCC 29213 biofilm formation was decreased of 97% and 90%, respectively The V9T14 biosurfactant active on the Gram-negative strain was ineffective against the Gram-positive and the opposite for the V19T21 This activity was observed either by coating the polystyrene surface or by adding the biosurfactant to the inoculum Two fractions from each purified biosurfactant, obtained by flash chromatography, fractions (I) and (II), showed that fraction (II), belonging to fengycin-like family, was responsible for the anti-adhesion activity against biofilm of both strains

Rhamnolipid biosurfactants as new players in animal and plant defense against microbes.

Abstract: Rhamnolipids are known as very efficient biosurfactant molecules. They are used in a wide range of industrial applications including food, cosmetics, pharmaceutical formulations and bioremediation of pollutants. The present review provides an overview of the effect of rhamnolipids in animal and plant defense responses. We describe the current knowledge on the stimulation of plant and animal immunity by these molecules, as well as on their direct antimicrobial properties. Given their ecological acceptance owing to their low toxicity and biodegradability, rhamnolipids have the potential to be useful molecules in medicine and to be part of alternative strategies in order to reduce or replace pesticides in agriculture.

Microbial biosurfactants as additives for food industries

Abstract: Microbial biosurfactants with high ability to reduce surface and interfacial surface tension and conferring important properties such as emulsification, detergency, solubilization, lubrication and phase dispersion have a wide range of potential applications in many industries. Significant interest in these compounds has been demonstrated by environmental, bioremediation, oil, petroleum, food, beverage, cosmetic and pharmaceutical industries attracted by their low toxicity, biodegradability and sustainable production technologies. Despite having significant potentials associated with emulsion formation, stabilization, antiadhesive and antimicrobial activities, significantly less output and applications have been reported in food industry. This has been exacerbated by uneconomical or uncompetitive costing issues for their production when compared to plant or chemical counterparts. In this review, biosurfactants properties, present uses and potential future applications as food additives acting as thickening, emulsifying, dispersing or stabilising agents in addition to the use of sustainable economic processes utilising agro-industrial wastes as alternative substrates for their production are discussed. V C 2013 American Institute of Chemical Engineers Biotechnol. Prog., 000:000–000, 2013