Velizar Gochev

Velizar Gochev
Plovdiv University "Paisii Hilendarski" · Department of Biochemistry and Microbiology

About

117
Publications
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1,492
Citations
Citations since 2016
32 Research Items
1169 Citations
2016201720182019202020212022050100150200
2016201720182019202020212022050100150200
2016201720182019202020212022050100150200
2016201720182019202020212022050100150200

Publications

Publications (117)
Article
Full-text available
A low-cost disposable lipase activity sensor was developed and characterized overcoming the main drawbacks of the already existing disposable ones: insufficient reproducibility to be applied for automatic lipase activity quantification and complicated and long manual analytical procedure performed by qualified personnel. The sensor is based on a ca...
Article
Full-text available
Pretreated waste Streptomyces fradiae biomass was used as biosorbent to remove tetracycline (TC) from model aqueous solutions. The biosorption study was conducted in a batch system to evaluate the impact of initial pH, biosorbent dosage, initial TC concentration and contact time. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models were appli...
Article
Full-text available
Laurel (Laurus nobilis L.) is a plant species from Lauraceae family, and is native to the Mediterranean region. The goal of this study was to compare chemical composition of laurel leaves and antibacterial activity of its essential oil (EO) from wild-grown trees in Greece and Georgia. The laurel leaves from the two native habitats had dissimilar co...
Article
A laponite modified carbon paste electrode was prepared and applied for the 2,4‐dichlorophenol (2,4‐DCP) voltammetric determination. Kinetic and equilibrium data for 2,4‐DCP adsorption by laponite in aqueous dispersions demonstrated that the adsorption process obeyed a pseudo first order kinetic model and was consistent with the formation of adsorb...
Article
An activated carbon nanopowder modified glassy carbon electrode (AC‐GCE) was constructed for the sensitive determination of methyl parathion by adsorptive differential pulse anodic stripping voltammetry. The simple and rapid modification procedure included only drop‐coating the electrode surface with a laponite stabilized activated carbon nanopowde...
Article
Full-text available
The essential oil of Matricaria chamomilla L., which is commonly used for medicinal and cosmetic purposes, can be differentiated between several chemotypes. In the current study, six essential chamomile oil samples of various origins (four of commercial sources, one of cultivation, one of wild collection) were examined regarding their composition a...
Article
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N. glutinosa L. is a relatively less studied Nicotiana species (Solanaceae), although there are data about its importance as a model plant in viral control studies, as a gene donor in tobacco hybridization and as a source of agents with insecticidal or fungicidal effects. The biological activities of the species were associated mostly with the pres...
Article
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Essential oils and hydrosols of two cultivars of muscadine grapes (Muscadinia rotundifolia (Michx.) Small.) were obtained by hydro-distillation of flowers and berry skins. Twenty-three volatile compounds were identified in essential oils from the muscadine flowers, and twenty volatiles in their corresponding hydrosols. The composition of volatiles...
Article
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Bay laurel ( Laurus nobilis L.) is an evergreen tree. The objective of this study was to determine the chemical composition (polyphenols, essential oil [EO], lipid fraction, cellulose, and protein content) of laurel fruits collected from Greece (Mount Athos) and Georgia (the village of Meria), and to evaluate the antimicrobial activity of laurel fr...
Article
A simple technique for the construction of a versatile diazirine‐functionalized nanostructured platform for enzymes photografting and electrochemical biosensing was proposed in this work. The feasibility of the approach was proved by photo crosslinking of an enzyme, tyrosinase, to diazirine‐activated aminated carbon nanotubes coated glassy carbon e...
Article
The high resolution second order voltammetric technique, Differential Alternative Pulse Voltammetry (DAPV), was applied for the simultaneous quantification of the mononitrophenol (NP) isomers. Complete resolution of the three isomers was achieved at concentration ratios as high as 1 : 5, employing the corresponding anodic and cathodic peaks appeare...
Article
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Waste biomass from Bacillus cereus immobilized in sodium alginate and co-immobilized with activated carbon or with bentonite into alginate gel was studied for Pb(II), Cd(II) and Hg(II) removal from aqueous solutions. The composite biosorbent consisting of waste B. cereus biomass co-immobilized with activated carbon into alginate beads was selected...
Article
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Microbial communities drive the biogeochemical cycles in wetlands and provide a number of ecosystem services. They underpin soil function, and are easily impacted by anthropogenic pressure. This study examined the bacterial microbiome in the natural wetland of Zlato Pole and the protected, periodically flooded rice paddies in the Maritsa River Basi...
Article
Intensive industrial and urban growth has led to the release of increasing amounts of environmental pollutants. Contamination by metals, in particular, deserves special attention due to their toxicity and potential to bioaccumulate via the food chain. Conventional techniques for the removal of toxic metals, radionuclides and precious metals from wa...
Article
The second order voltammetric technique of high resolution, Differential Alternative Pulses Voltammetry (DAPV), was applied for the simultaneous determination of hydroquinone (HQ) and catechol (CC) on bare spectroscopic graphite electrode. Well resolved anodic and cathodic peaks situated on both sides of the zero line were obtained, while the diffe...
Article
Full-text available
An electrochemical organophosphorus hydrolase-based sensor for direct organophosphorus pesticides determination was developed, analytically characterized and applied for paraoxon quantification. The biosensing platform was constructed by one-step electrodeposition onto the surface of a glassy carbon electrode of a bionanocomposite of chitosan with...
Article
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The authors describe a graphite immobilized bismuth film electrode with enhanced sensitivity for the organophosphorus pesticide paraoxon. The film was formed by ex-situ electroplating of bismuth onto the large surface of a glassy carbon electrode modified with graphite nanopowder (Bi/Gr/GCE). The modified GCE was characterized by chronoamperometry...
Article
An amperometric bi-enzyme sensor for detection of organophosphorus pesticides (OPs) with phenolic leaving groups, which are not electroactive, is presented in this work. The biosensing platform was created by a simple, controllable, and reproducible one-step electrodeposition onto the surface of a glassy carbon electrode of a chitosan bionanocompos...
Article
The essential oil of Bunium persicum collected from cultivated sources in the cold desert area of Lahaul-Spiti is described for its antimicrobial, larvicidal, and biting deterrent activities. Additionally, odor characterization is given. The chemical composition of the essential oil was analyzed by simultaneous GC-MS and GC-FID. γ-Terpinene and p-c...
Article
Background:The high acute toxicity of the organophosphorus pesticides (OPs) imposes the development of simple, rapid, sensitive, and reasonably priced analytical methods for their in situ determination. The electrochemical biosensors-based techniques for OPs determination complete with these requirements. Objective: The objective of this work is th...
Article
Full-text available
Pretreated waste Streptomyces fradiae biomass was utilized as an eco-friendly sorbent for Congo Red (CR) and Methylene Blue (MB) removal from aqueous solutions. The biosorbent was characterized by Fourier transform infrared spectroscopy. Batch experiments were conducted to study the effect of pH, biosorbent dosage, initial concentration of adsorbat...
Chapter
The aim of present chapter is to gather the information about chemical composition, biological activities and possible applications of essential oils from seven different species of Genus Salvia growing in Bulgaria (S. officinalis L., S. sclarea L., S. tomentosa Mill, S. scabiosifolia Lam., S. ringens Sibth. et Sm., S. amplexicaulis Lam. and S. aet...
Article
The development of highly sensitive amperometric biosensors for dopamine determination using commercially available SPEs in combination with the PVA-AWP photopolymer as the enzyme immobilization matrix is described in this work. This research focuses on (i) the optimization of the conditions for SPE biofunctionalization by tyrosinase entrapment in...
Article
Low-alcohol beer can be obtained by physical and biological methods. The group of biological methods includes modification of the mashing regimes and changes in the fermentation process. The aim of the present work was to study two mashing regimes for low-alcohol beer production. The increase in the mashing duration at 50 °C led to a linear increas...
Conference Paper
Full-text available
En este trabajo se presentan y analizan los resultados de la evaluación de inhibición del crecimiento microbiológico a las que fueron sometidos extractos de dos plantas nativas del Valle de Mexicali, México, contra cepas de interés biomédico. Mediante una maceración en frío se obtuvieron extractos metanólicos y etanólicos de cachanilla (Pluchea ser...
Article
Full-text available
An overview on the progress in the organophosphorus hydrolase based electrochemical sensors design and application for direct organophosphorus pesticides quantification is presented in this work. The key analytical performances of the enzyme and of the bacterial potentiometric and amperometric organophosphorus hydrolase based sensors, as well as th...
Article
Background: The clinical and therapeutic significance of dopamine, known as important hormone and neurotransmitter, motivated the development of the sensitive, rapid, and cost effective electrochemical methods for its determination. Methods: This review comments on the advances in the electrochemical sensing and biosensing of dopamine, covering the...
Chapter
The chemical composition of the oil fruits from of Schizandra chinensis (Turcz.) Baill, cultivated in Bulgaria were analyzed using GC and GC/MS. The major constituents (over 3%) of the essential oil (1.65%) were found to be ?-himachalene (10.83%), ?-ylangene (10.50%), ?-himachalene (9.02%), schisandrin (8.23%), ?-chamigrene (6.44%) and ?-muurolene...
Article
Full-text available
In the present study dead Streptomyces levoris biomass loaded on silica gel 60 was applied as an eco-friendly solid phase extractor for copper (II) preconcentration prior to its determination by flame atomic absorption spectrometry. The influences of different parameters such as pH of the sample solution, amount of solid phase, type and concentrati...
Article
Full-text available
Химичният състав на екстракт от цвят на невен (Calendula officinalis L.), получен при екстракция с 1,1,1,2-тетрафлуороетан е изследван чрез GC and GC/MS анализ. Главните компоненти (концентрация над 3 %) в екстракта са: α-бизаболон оксид (8,33 %), β-фарнезен (8,10 %), α-бизаболон оксид А (7,28 %), α-пинен (6,84 %), γ-кадинен (5,47 %), р-цимен (5,44...
Article
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Antimicrobial activity of nineteen neo-clerodane diterpenoids, isolated from the acetone extracts of the aerial parts of Scutellaria and Salvia species (Lamiaceae) were tested against thirteen strains belonging to nine different species of pathogenic and food spoilage bacteria Aeromonas hydrophila, Bacillus cereus, Escherichia coli, Listeria monocy...
Article
Full-text available
Various essential oils have potential for use in alternative strategies for plant pathogen control. In this work twelve essential oils and several of their components were screened for antibacterial activity against the causative agents of bacterial spot of pepper – Xanthomonas vesicatoria and Xanthomonas euvesicatoria, using the agar diffusion met...
Article
Full-text available
The essential oils of two Lamiaceae cultivated in Western Himalaya were examined on their antimicrobial, biting deterrent as well as larvicidal activity. Additionally their odors are described and their chemical compositions analyzed by GC-MS are given. The main component of Nepeta cataria oil was 4a,7,7a-nepetalactone (85%), whereas camphor (27%)...
Article
Full-text available
Chemical composition and bioactivity of essential oil from Salvia tomentosa Mill. natively grown in Bulgaria were investigated. GC-MS analysis identified 60 compounds which represented 98% of the oil constituents. The prevalent constituents were monoterpenes with eight dominant compounds being identified: borneol (10.3%), β-pinene (9%), camphor (7....
Article
The Himalayan region is very rich in a great variety of medicinal plants. In this investigation the essential oils of two selected species are described for their antimicrobial and larvicidal as well as biting deterrent activities. Additionally, the odors are characterized. Analyzed by simultaneous GC-MS and GC-FID, the essential oils' chemical com...
Article
The chemical composition of hyssop oil from Bulgaria was determined by gas chromatography with flame ionization detection and gas chromatography-mass spectrometry on two different chromatographic columns. The quantity of identified compounds was shown correspond to 97.2% and 98% of the total oil content. Among the detected compounds, cis-pinocampho...
Article
Full-text available
Nerolidol and its derivatives, namely cis-nerolidol, O-methyl-nerolidol, O-ethyl-nerolidol, (-)-alpha-bisabolol, trans,trans-farnesol and its main natural source cabreuva essential oil, were tested for their antimicrobial activity against airborne microbes and antifungal properties against plant pathogens. Among the tested compounds, alpha-bisabolo...
Article
Full-text available
Biosorption of Pb(II) ions from a model solution was investigated using Streptomyces fradiae biomass as biosorbent pretreated with sodium hydroxide. The mycelium is a waste product from the biotechnological production of the macrolide antibiotic tylosin in the pharmaceutical industry. The biosorption study was conducted in a batch system with respe...
Article
Concentrated extraction products (concrete, resinoid, extract with 1,1,1,2-tetrafluoroethane) from the leaves of three Bulgarian types of tobacco (Nicotiana tabacum L.) – flue-cured Virginia, Burley and Oriental, have been obtained. The products, as well as the respective essential oils, have been characterized by their chemical composition (mono-,...
Article
The essential oils of two Lamiaceae cultivated in Western Himalaya were examined on their antimicrobial, biting deterrent as well as larvicidal activity. Additionally their odors are described and their chemical compositions analyzed by GC-MS are given. The main component of Nepeta cataria oil was 4aα,7α,7aα-nepetalactone (85%), whereas camphor (27...
Article
Full-text available
The aim of the present study was to carry out a preliminary assessment for the occurrence of bacterial strains resistant to frequently used antibiotics in the sediments beneath the sturgeon cage farm in Kardzhali Dam (Bulgaria). Samples were taken from the top 2 cm of sediments under a fish farm and from a control station in the aquatory of the res...
Article
Full-text available
The essential oils of two representatives of the Lamiaceae, Dracocephalum heterophyllum Benth. and Hyssopus officinalis L., are described for their antifungal, antibacterial, larvicidal and inect biting deterrent activities. Additionally, the chemical compositions of the essential oils, analyzed by simultaneous GC-MS and GC-FID, and odor descripti...
Article
Full-text available
Waste Streptomyces fradiae biomass from pharmaceutical industry was successfully used for Zn(II) removal from aqueous solutions. In the present study process parameters (initial pH of the solution, amount of biomass, initial metal concentration, stirring speed and contact time) and their influence on Zn(II) biosorption were investigated and optimiz...
Article
Full-text available
The biosorption potential of waste pretreated brewery biomass for Zn (II) removal from aqueous solutions was evaluated. To understand the role of functional groups in Zn (II) uptake some of the functional groups were chemically modified. Blocking of carboxyl, amino, phosphate and sulfhydryl functional groups decreased the Zn (II) uptake by 87.88%,...
Conference Paper
Full-text available
The chemical composition of extract from lavender (Lavandula angustifolia Mill.) by extraction with tetrafluoroethane was analyzed using GC and GC/MS. The main compounds (concentration higher than 3%) of extract were: linalool (32.48%), linalyl acetate (22.98%), borneol (5.12%), cis-linaloloxide (4.49%), (E)-β-farnesene (4.10%), lavandulol (4.22%)...
Article
Full-text available
An approach for precision improvement in organophosphorus pesticides determination was developed, applied and characterized. The enzyme organophosphorus hydrolase was employed as specific agent for electrode surface modification, and the pulsed amperometric detection for 66.6 ms was applied for the hydrolysis products detection. Pulsed electrochemi...
Article
Artemisia species possess pharmacological properties that are used for medical purposes worldwide. In this paper, the essential oils from the aerial parts of Artemisia nilagirica and Artemisia maritima from the western Indian Himalaya region are described. The main compounds analyzed by simultaneous GC/MS and GC/FID were camphor and 1,8-cineole fro...
Article
Full-text available
Four hydrophilic polymers in the form of beads – chitosan, alginate, alginate/polyvinyl alcohol (PVA), and chitosan-coated alginate – were used as supports for lipase immobilisation. Hydrogel beads were characterised by bead-size-distribution estimation, surface morphology studies, and polymer interactions assessment. Matrix performances – loading...
Conference Paper
Full-text available
The chemical composition of extract from the Bulgarian essential oil bearing plants from Lamiaceae family - peppermint (Mentha piperita L.) by extraction with C2H2F4 (1,1,1,2-tetrafluorethane) was analyzed using GC and GC/MS. The main compounds (concentration higher than 3 %) of extract was as follows: menthone (30.54 %), menthol (21.12 %), menthyl...
Article
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The biosorption potential of heat inactivated mycelium of Trametes versicolor, free and immobilized in Ca-alginate and co- immobilized in Ca-alginate with bentonite and activated carbon, for Cu(II) removal from aqueous solutions was investigated. Among the studied biosorbents heat inactivated fungal mycelium co-immobilized in Ca-alginate with activ...
Article
Full-text available
The rates of hydrogen production by B10 and the genetically modified IR3 varieties of the bacterial strain R. capsulatus employing DL-sodium lactate as a carbon source and parts of the visible spectrum light as energy source were compared. The influence of parameters such as: light spectrum (blue, green, red, white light), light luminance (from 250...
Article
Full-text available
Antimicrobial activity of two trade lots of essential oils from Rosa alba L. against Gram-positive bacteria, belonging to genera Staphylococcus and Bacillus, Gram-negative bacteria, belonging to genera Escherichia, Pseudomonas, Salmonella and Citrobacter and yeasts, belonging to genera Candida was investigated. It was determined that Gram-positive...
Article
Full-text available
At current study the antimicrobial activity of Origanum vulgare, Satureja montana, Thymus vulgaris, Pimenta dioica and Syzygium aromaticum against psychrotrophic microorganisms, isolated from spoiled chilled meat products was investigated. MIC, MBC and MFC of the essential oils were determined both at 37° and 4°C. Antimicrobial activity of the esse...
Article
Full-text available
At present study the biosorption potential of dead biomass of Saccharomyces cerevisiae immobilized in Ca-alginate and co- immobilized in Ca-alginate and bentonite and Ca-alginate and activated carbon for removal of Cu (II) from model solutions was investigated. The highest biosorption potential demonstrated the biosorbent of S. cerevisiae co-immobi...
Article
Full-text available
Antimicrobial activity of essential oils from Origanum vulgare, Satureja montana, Thymus vulgaris, Pimenta dioica and its major constituents against spoilage and pathogenic microorganisms isolated from meat products was evaluated. Among used test microorganisms Pseudomonas aeruginosa demonstrated the highest resistance and Staphylococcus aureus dem...
Article
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The aim of present study was to investigate sanitary-hygienic status of some of the most popular meat products from trade network. Microbiological monitoring of refrigeratory stored minced meat and boiled-stewed sausages was carried out in hygienic, pathogenic and spoilage microorganisms comparing to boiled-stewed sausages. Following strains were i...
Article
Full-text available
The chemical composition of extract from basil (Ocimum basilicum L.) by extraction with C 2 H 2 F 4 (1,1,1,2-tetrafluoroethane) was analyzed using GC and GC/MS. The main compounds (concentration higher than 3 %) were: estragole (46.97 %), linalool (10.64 %), methyl eugenol (8.94 %), 1,8-cineole (3.74 %) and -bisabolene (3.06 %). The studied extrac...
Article
Abstract The constituents of essential oils, obtained from different aerial parts (leaves and flowers) of Salvia ringens Sibth. et Sm. growing wild in Bulgaria, have been analyzed by GC-MS. The yields of leaves and flowers oils were similar (0.03 % v/w and 0.04 % v/w). 60 compounds were identified in both oils, which correspond to 97.7 % and 97.3 %...
Article
Full-text available
The chemical composition of extract from the dill (Anethum graveolens L.) by extraction with tetrafluoroethane was analyzed using GC and GC/MS. The main compounds (concentration higher than 3 %) of extract were: D-carvon (53,12 %)and limonen (37,12 %). The studied extract demonstrated antimicrobial activity against Gram-positive bacteria. The extra...
Article
Full-text available
Extracellular lipase production by Penicillium chrysogenum, Trichoderma harzianum and Aspergillus flavus was carried out through solid state fermentation using agro-industrial residues as substrates. For all three strains, the growth temperature was 29 +/- 1 degrees C, and 65 % w (g/gds) moisture content. The effect of three factors on lipase produ...
Article
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The growing interest in lipase production is related to the potential biotechnological applications that these enzymes present. Current studies on lipase production by solid state fermentation involve the use of agro-industrial residues, aiming at increasing the economic attractiveness. Based on these aspects, the objective of this work was to inve...
Article
Various species of Thymus L. are used for medical, flavouring and food preservation purposes. In the current study, the essential oils of inflorescences and leaves of four thyme species (T. broussonetii, T. pallidus, T. maroccanus and T. satureioides) from SouthWestern Morocco were analysed by simultaneous GC-FID and GC-MS. The main compound was ca...
Article
Full-text available
Various species of Thymus L. are used for medical, flavouring and food preservation purposes. In the current study, the essential oils of inflorescences and leaves of four thyme species (T. broussonetii, T. pallidus, T. maroccanus and T. satureioides) from South-Western Morocco were analysed by simultaneous GC-FID and GC-MS. The main compound was c...
Article
The antifungal activities of peppermint essential oils obtained from standard cul-tivar, two newly selected Mentha x piperita L. and allopolyploid hybrid of Mentha x piperita L. x Mentha arvensis, growing in Bulgaria, were investigated against 15 clinical isolates of Candida albicans (5 oropharyngeal, 5 vaginal and 5 skin damaging strains) and C. a...
Article
The antifungal activity of eugenol containing essential oils - pimento oil (Pimenta dioica (L.) Merr), bay oil (Pimenta racemosa (Mill.) J. W. Moore), clove oil (Szygium aromaticum (L.) Merr. & M. Perry), and cinnamon oil (Cinnamomum zeylanicum Blume) was investigated against 38 clinical isolates of Candida albicans (12 oropharyngeal, 16 vaginal an...
Article
Antifungal activities of essential oils of Salvia lavandulifolia, Salvia officinalis and Salvia sclarea against various pathogenic Candida species were investigated. It was shown that antifungal activity of sage essential oils depends on their Chemical composition. The strongest anti-fungal activity possesses the essential oil of S. lavandulifolia,...
Article
The chemical composition of historical rose oil (produced in 1944) from Bulgaria was investigated by GC and GC-MS. The rose oil was found to be rich in citronellol (23.4 %), geraniol (19.0 %), nonadecane (11.9 %), and nerol (7.5 %). In general, the chemical composition of this historical rose oil corresponded exactly to the criteria stated in the c...