Browsing by Author "Marinkova D."
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Item Antimicrobial activity of Bulgarian products and their extracts containing bioactive components(2015-01-01) Marinkova D.; Danalev D.; Genchev G.Phytoncides are organic compounds, produced by plants in order to protect them from different microorganisms. Over the years a number of plants and their extracts are subjected to investigation of their antibacterial properties. The increase in the number of side reactions caused by antibiotics, and other drugs used in medical practice, turned back the attention of many scientists to studies of the properties and antibacterial activity of products from national cuisine. This paper reports on the antibacterial properties of honey, garlic, onions and their extracts, produced in Bulgaria. Arthrobacter oxydans 1388 (an example for Gram+ microorganism) and Pseudomonas fluorescens 1442 (an example of a Gram- microorganism) were selected as test microorganisms. Our studies have shown that Arthrobacter oxydans are sensitive to the antimicrobial activity of honey, while the Pseudomonas fluorescens show resistance. Garlic extracts have shown good activity against both Arthrobacter oxydans and Pseudomonas fluorescens.Item Antimycotic activity of sumac extract in composites based on epoxidized natural rubber for application in footwear soles production(2020-01-01) Dishovsky N.; Marinkova D.; Raykova R.; Vladimirova L.Biofilms are attached to different kinds of surfaces or associated with interfaces. The microbial communities are often composed of multiple species, which interact between each other. Attachment is complex process, regulated by diverse characteristics of the growing media, substrates and cell surface. Biofilms have different effects, which can affect changes in surface properties of polymer carriers. Accumulated biomass may provoke negative effects by direct attack, which leads to destruction of polymer matrixes. An option to solve the problem is introduction of bioactive ingredient into the composite. The aim of our study was to find and propose bioactive ingredients, derived from renewable sources, particularly such exhibiting of antimycotic influence, which can be included to elastomeric composite materials. These materials can be used for obtaining of winter footwear soles with adhesion, increasing to various types of icy surfaces. The influence of introduced antimycotic additive, extracted from Cotinus coggygria plant, was investigated. Antimycotic activity of obtained plant extracts against two eukaryotic strains was investigated by diffusion method in agar broth. The formation of biofilms from Candida lypolitica and Candida albicans strains onto natural rubber vulcanizates, kinetics and growth of biofilms strains were also observed.Item Co-immobilization of peroxidase and tyrosinase onto hybrid membranes obtained by the sol-gel method for the construction of an optical Biosensor(2013-09-04) Yotova L.; Yaneva S.; Marinkova D.; Serfaty S.The sol-gel method was used to synthesise two groups of hybrid membranes from silica precursors: ETMS (ethyltrimethoxysilane) and MTES (methyltriethoxysilane), and cellulose derivatives. Peroxidase isolated from horseradish and tyrosinase isolated from mushrooms was immobilized by covalent immobilization. The kinetic parameters of the isolated enzymes, pH and temperature optimum were studied. The results of this study showed a higher relative and residual activity of the enzyme when immobilized on membranes containing cellulose acetate propionate with high molecular weight CAP/H. Membranes with the best parameters were used as carriers of the multienzyme peroxidase-tyrosinase system. An optical biosensor with an oxygen electrode was constructed. Potentially, the sensor could be used for monitoring of the environment, detecting phenols in wastewater, food stuff, and in medicine.Item Influence of Ni2+ on urease activity produced by biofilms of Arthrobacter oxydans 1388(2014-01-01) Marinkova D.; Yotova L.; Ringeard J.; Griesmar P.New TiO2-based hybrid materials composed of an organic polymer, cellulose acetate butyrate and copolymer of acrylonitrile acrylamide (AN + AA) were prepared. The effectiveness of immobilization of microbial strain Arthrobacter oxydans 1388 on the newly synthesized hybrid membranes was investigated by biochemical methods. The obtained results revealed that the matrix more suitable for biofilm formation was composed of organic polymers without a metal component in the membrane composition. The influence of Ni2+ on urease activity produced by biofilms was investigated. The experimental results demonstrated that 2 mg L -1 concentration of Ni2+ in the nutrient medium is more appropriate for biofilm proliferation. © 2014 The Author(s). Published by Taylor & Francis.Item Investigation of formation, development and application of arthrobacter oxydans 1388 biofilm(2009-01-01) Yotova L.; Marinkova D.; Mironova V.; Dulgerova R.Biofilms are microbial communities attached to different kinds of surfaces or associated with interfaces. These microbial communities are often composed of multiple species that interact with each other and their environment. The determination of biofilm architecture, particularly the spatial arrangement of microcolonies (clusters of cells) relative to one another, has profound implications for the function of these complex communities. Numerous new experimental approaches and methodologies have been developed in order to explore metabolic interactions, phylogenetic groupings, and competition among members of the biofilm. Bioremediation is an innovation technology, which controls the pollutants, using biological systems for degradation or transformation of different toxic compounds Taking in consideration the efficiency of the bioremediation by means of different microbial strains the aim of this study is to investigate the creation and application of biofilms for wastewater treatment. The dynamics of the formation of a biofilm from cells of strain Artrobacter oxydans 1388 on newly synthesized different carriers was investigated by scanning electron microscopy (SEM). Extracellular polymeric substances (EPS) are biopolymers of microbial origin in which biofilm microorganisms are embedded. Exopolysaccharides and proteins are one of the main factors in biofilm formation, evidence for microenviromental changes of microbial cells. In this study the biofilm growth and characteristics are researched by biochemical methods of investigation of extacellular polymeric substances. The microbial cells are immobilized by two methods—covalently binding and adhesion to the different polymeric matrixes. Matrixes were obtained on the base of copolymer of acrylonitrile with acrylamide and mixed with cellulose acetate butyrate. In this case they were with high mechanical stability. Two methods of immobilization were applied. The obtained results demonstrated that better and more effective was the covalent binding. © 2009 Taylor and Francis Group, LLC.Item Production and chracterization of lipase from pseudozyma antarctica NBIMCC 8340(2015-01-01) Borisov B.; Manova D.; Marinkova D.; Yotova L.; Danalev D.Lipases are serine hydrolases, defined as triacyl-glycerol acylhydrolases. They catalyze both hydrolytic and synthetic reactions showing substrate, regio- and stereo selectivity. The psyhrophilic strain Pseudozyma antarctica, isolated in the cold conditions of the Antarctica, can produce a thermostable extracellular lipase. In this work we report the synthesis of an extracellular lipase from Pseudozyma antarctica. The strain was cultured in flasks and various parameters were monitored during the proliferation process. Several cultivation procedures were done in order to find optimal conditions. Further, activity of the crude lipase, its temperature and pH optimum were determined using a potentiometric method. We found temperature optimum at 60°C and pH optimum at pH 8.0. The determined specific activity of the crude lipase was 97,2 U/mg. Activity and protein content of the ``crude`` post cultivation liquid were also determined.Item Synthesis and investigation of the properties of hybrid materials for enzyme immobilization(2018-01-01) Yaneva S.; Semerdzhieva V.; Raykova R.; Marinkova D.; Chernev G.; Iliev I.; Yotova L.The chemical nature of carriers for enzyme immobilization plays an important role for retention of the enzyme activity and stability. Two new materials are synthesized for enzyme immobilization based on trimethoxy silane/cellulose acetate butyrate/poly (amido amine) dendrimers (TMOS/CAB/PAMAM) and methyltriethoxy silane/cellulose acetate propionate/ poly (amido amine) dendrimers (MTES/CAP/PAMAM). The synthesis is carried out via the sol-gel method, which allows the preparation of porous glasses through hydrolysis and poly-condensation at a low temperature using high purity initial materials. The PAMAM dendrimers are mono-dispersive, well defined and have a developed three dimensional structure of a high functional groups concentration. The obtained materials are used to investigate the properties of immobilized enzymes such as lipoxygenase and laccase. These enzymes are widely used in industry as bleaching agents. There is also data on application of laccase and lipoxygenase in preparation of biosensors for toxic pollutants determination. Biosensors with immobilized laccase are used to determine phenolic compounds, whereas immobilized lipoxygenase is applied to biosensors formulation for determining Aflatoxin B1 presence.Item Valorization of a plant β-amylase: Immobilization and dataset on the kinetic process(2018-02-01) Lahmar I.; Radeva G.; Marinkova D.; Velitchkova M.; Belghith H.; Ben Abdallah F.; Yotova L.; Belghith K.The data presented in this article are related to the research article titled “Immobilization nd topochemical mechanism of a new β-amylase extracted from Pergularia tomentosa” (Lahmar et al., 2017) [1]. This article documented information on the determination of the molecular weight of the β-amylase, the method of its immobilization and a comparison of the kinetic mechanism between the free and the immobilized forms by a mathematical method. Fresh Pergularia tomentosa was collected from Tunisia and a special method for β-amylase extraction was followed (Yotova et al., 2000) [2]. Public dissemination of this dataset will allow further analyses of the data.