
Karen TrchounianYerevan State University | YSU · Department of Biochemistry Microbiology and Biotechnology
Karen Trchounian
PhD, D.Sc
About
143
Publications
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Introduction
Karen Trchounian currently works at Depatment of Biochemistry, Microbiology and Biotechnology and at the Scientific-Research Institute of Biology, Yerevan State University. Karen does research in Biotechnology, Biochemistry, Cell Biology and Microbiology. Their current project is 'New approach of carbon containing end products and wastes utilization: hydrogen production by pure and mixed cultures of dark- and photo-fermentative bacteria.'
Additional affiliations
Education
October 2013 - February 2017
June 2011 - October 2013
June 2009 - May 2011
Publications
Publications (143)
The extremophile microorganism Thermus scotoductus primarily exhibits aerobic metabolism, though some strains are capable of anaerobic growth, utilizing diverse electron acceptors. We focused on the T. scotoductus K1 strain, exploring its aerobic growth and metabolism, responses to various carbon sources, and characterization of its bioenergetic an...
This study explores the molecular mechanisms behind the differential responses of Saccharomyces cerevisiae industrial strains (ATCC 9804 and ATCC 13007) to osmotic stress. We observed that, in contrast to ATCC 9804 strain, sodium flux in ATCC 13,007 is not N, N’-dicyclohexylcarbodiimide (DCCD)-sensitive under osmotic stress, suggesting a distinct i...
The effect of silver nanoparticles (Ag NPs) obtained in the presence of royal jelly (RJ) on the growth of yeast Candida guilliermondii NP-4, on the total and H⁺-ATPase activity, as well as lipid peroxidation process and antioxidant enzymes (superoxide dismutase (SOD), catalase) activity was studied. It has been shown that RJ-mediated Ag NPs have a...
During the last decade the health of honeybee is endangered because of many different pathogens, that is why the isolation of new lactic acid bacteria from honeybees' gut microbiotas, revealing of their strong antibacterial activity will help to create some products for protection of bees’ health.
New Gram-positive mesophilic strains were isolated...
This study investigates the effects of X-radiation on ATPase activity and antioxidant enzyme activity, particularly enzymes involved in proline biosynthesis, in yeast C. guilliermondii NP-4. Moreover, the study examined the post-irradiation repair processes in these cells. Results showed that X-irradiation at a dose of 300 Gy led to an increase in...
Ralstonia eutropha is a facultative chemolithoautotrophic aerobic bacterium that grows using organic substrates or H2 and CO2. Hydrogenases (Hyds) are synthesized under lithoautotrophic, or energy-limited heterotrophic conditions and are used in enzyme fuel cells (EFC) as anodic catalysts. The effects of chemically synthesized gold nanoparticles (A...
Escherichia coli performs mixed-acid fermentation and produces molecular hydrogen (H2) via reversible hydrogenases (Hyd). H2 producing activity was investigated during hyper- and hypo-osmotic stress conditions when a mixture of carbon sources (glucose and glycerol) was fermented at different pHs. Hyper-osmotic stress decreased H2 production rate (V...
The development of net-zero emission fuels is a priority area of modern research due to the imminent reduction of fossil fuel reserves and environmental problems caused by their combustion. One of the promising fuels is hydrogen, which has a high heat of combustion and is eco-friendly, forms water as the only byproduct. Recently, methods of hydroge...
Ion homeostasis is pivotal for numerous cellular functions and adaptation. Investigation of the relationship between K+ and H+ transporters and energy exchange processes of S. cerevisiae ATCC 9804 and ATCC 13007 strains will be crucial to enhance resistance to osmotic stress and improve industrial processes. Specific growth rate (SGR), pH and oxida...
Short-chain fatty acids like propionic (PPA) and valproic acids (VP) can alter gut microbiota, which is suggested to play a role in development of autism spectrum disorders (ASD). In this study we investigated the role of various concentrations of PPA and VP in gut enteric gram-negative Escherichia coli K12 and gram-positive Enterococcus hirae ATCC...
Inspired by the concept of organic waste valorisation and heading towards a sustainable economy, a green chemistry extraction technique involving supercritical carbon dioxide (SC-CO2) along with water as a co-solvent was employed for the main winery by-product (grape pomaces). The objective was to selectively extract high-value added molecules, in...
Over the past few decades, antibiotic resistance of microorganisms became a great biomedical challenge. Silver nanoparticles (AgNPs) mediated from plant extract are
one of the most common nanoparticles with wide applications in various fields, since they have better antibacterial potential against various bacteria. Moringa oleifera is herb rich in...
Side streams of the dairy industry are a suitable nutrient source for cultivating microorganisms, producing enzymes, and high-value chemical compounds. The heterotrophic Escherichia coli and chemolithoautotroph Ralstonia eutropha are of major biotechnological interest. R. eutropha is a model organism for producing O2-tolerant [NiFe]-hydrogenases (H...
Ralstonia eutropha H16 is a chemolithoautotrophic bacterium with O2-tolerant hydrogenase (Hyds) enzymes. Hyds are expressed in the presence of gas mixtures (H2, O2, CO2) or under energy limitation and stress conditions. O2-tolerant Hyds are promising candidates as anode biocatalysts in enzymatic fuel cells (EFCs). Supplementation of 0.5% (w/v) yeas...
Escherichia coli is able to ferment mixed carbon sources and produce various fermentation end-products. In this study, the function of FhlA protein in the specific growth rate (µ), metabolism, regulation of ΔpH and proton ATPase activity was investigated. Reduced µ in fhlA mutant of ∼25% was shown, suggesting the role of FhlA in the growth process....
Silver nanoparticles (Ag NPs) represent one of the most widely employed metal-based engineered nanomaterials with a broad range of applications in different areas of science. Plant extracts (PEs) serve as green reducing and coating agents and can be exploited for the generation of Ag NPs. In this study, the phytochemical composition of ethanolic ex...
Our study evaluates the possibility of side-streams of the dairy industry as a potential feedstock for microbial (R. eutropha, E. coli) biomass, hydrogen, and Hyds formation.
Currently, coffee consumption reached 9.92 million tons, being responsible for the generation of huge amounts of waste associated with coffee bean processing steps and further operations. Coffee silverskin (CS) and spent coffee grounds having high organic content are generated as a result of roasting and brewing processes. Escherichia coli wild‐typ...
The present study reveals a simple, non-toxic and eco-friendly method for the "green" synthesis of Ag-NPs using hydroponic and soil medicinal plant Stevia rebaudiana extracts, the characterization of biosynthesized nanoparticles, as well as the evaluation of their antibacterial activity. Transmission electronic microscopy (TEM) and Dynamic Light Sc...
In recent years silver nanoparticles (Ag NPs) gained increased and widespread applications in various fields of industry, technology, and medicine. This study describes the green synthesis of silver nanoparticles (Ag NPs) applying a low-molecular-weight fraction (LMF) of Royal Jelly, the nanoparticle characterization, and particularly their antibac...
In this study, alternative uses for lignocellulosic waste by considering them a source of eco-friendly and renewable energy generation with the application of the anaerobic digestion of treated and untreated waste for biogas and biohydrogen generation were investigated. The diluted sulfuric acid method was used for both the substrates and inoculum....
Hydrogen (H2) metabolism in Escherichia coli occurs via reversible membrane-associated hydrogenase enzymes (Hyd). Hyd-3 and Hyd-4 with formate dehydrogenase H (FDH-H) form formate hydrogen lyase complexes. The changes of metabolic pathways and ΔpH (pHin-pHex) regulation during fermentation of glucose, glycerol and formate in non H2-producing hypF (...
s submitted to the Congress are not peer-reviewed. In addition, abstracts are published as submitted and are not copyedited prior to publication. We are unable to make corrections of any kind to the abstracts once they are published.
Escherichia coli anaerobically utilize various carbon sources and produce hydrogen (H2) as fermentation end product. Twofold diluted mixture of 10% distiller’s grains (DG), 4% brewer’s spent grains (BSG), and 10% sugar beet molasses (SB) are favorable for enhanced H2 production compared to the single wastes. In wild type cells, H2 production was pr...
Escherichia coli anaerobically ferment glucose and perform proton/potassium exchange at pH 7.5. The role of hyf (hydrogenase 4) subunits (HyfBDF) in sensing different concentrations of glucose (2 g L−1 or 8 g L−1) via regulating H+/K+ exchange was studied. HyfB, HyfD and HyfF part of a protein family of NADH-ubiquinone oxidoreductase ND2, ND4 and N...
Physicochemical pretreatment of lignocellulosic corn fruit wastes (husk, shank, stalk) has been done. E. coli K12 growth, ORP kinetics, and H2 production were followed upon utilization of corn waste hydrolysates (CWH) separately and their mixture. During the bacterial log growth phase with the decrease of medium pH the readings of Pt electrode from...
A growing demand for the ecologically pure products brings us for searching novel biotechnological approaches for plant cultivation. One of these approaches is the in vitro cultivation and further acclimatization of valuable plant species. The object of our investigation was Ajuga reptance L. ornamental plant which possesses high metabolic activity...
Saccharomyces cerevisiae is an essential component of human civilization because of its extensive use in food industry. At the point of industrial usage it is very important to get large amount of biomass but many factors causes yeast's viability loss and death. The aim of this work was to study the peculiarities of growth parameters – specific gro...
Wine pH is acidic (>3,5), during wine
secondary faermantation and storage
lactic acid bacteria (LAB) enable to
survive in these acidic conditions. It was
known that LAB couldsurvive in low pH
by efflux of H ions trough plasmatic
membrane (PM) and subsequent
regulation of internal pH due to Fo F1 -
ATPase, which is N, N'-
dicyclohexylcarbodiimide (D...
During fermentation in Escherichia coli succinate is transported via Dcu transporters, encoded dcuA, dcuB, dcuC and dcuD although the role of DcuD protein has not been elucidated yet. It has been shown contribution of Dcu transporters in the N,N’-dicyclohexylcarbodiimide (DCCD) sensitive proton and potassium transport through the cytoplasmic membra...
This research is focused on the investigation of specific growth rate changes of $E.~coli$ wild type and mutant strains with defect of Hyd, FDH enzymes and FhlA regulatory protein in the presence of $N,N'$-dicyclohexylcarbodiimide (DCCD) and external formate various concentration during co-fermentation of glucose, glycerol and formate at pHs $5.5-7...
The application of green synthesis in nanotechnology is growing day by day. It’s a safe and eco-friendly alternative to conventional methods. The current research aimed to study raw royal jelly’s potential in the green synthesis of silver nanoparticles and their antibacterial activity. Royal jelly served as a reducing and oxidizing agent in the gre...
Escherichia coli is able to utilize the mixture of carbon sources and produce molecular hydrogen (H2) via formate hydrogen lyase (FHL) complexes. In current work role of transcriptional activator of formate regulon FhlA in generation of fermentation end products and proton motive force, N’N′‐dicyclohexylcarbodiimide (DCCD)‐sensitive ATPase activity...
A growing demand for the ecologically pure products brings us for searching novel biotechnological approaches for plant cultivation. One of these approaches is the in vitro cultivation and further acclimatization of valuable plant species. The object of our investigation was Ajugareptance L. ornamental plant which possesses high metabolic activity....
The impact of the four membrane-bound [NiFe]-hydrogenases (Hyd) of Escherichia coli on total H2-oxidizing activity during fermentation of a mixture of glucose, glycerol and formate at different pHs was examined. It was shown that Hyd-2 had a major contribution to total Hyd activity at pH 7.5 in early-stationary phase (24 h) cells, while the main co...
During fermentation Escherichia coli transport succinate mainly via Dcu family carriers. Current paper describes the role of externally added succinate on N’N’-dicyclohexylcarbodiimide (DCCD) sensitive ATPase activity and H+ flux depending on potassium ions. At pH 7.5 in wild type membrane vesicles DCCD-sensitive ATPase activity was the same as in...
After brewing roasted coffee spent coffee grounds (SCG) are generated being one of the daily wastes emerging in dominant countries with high rate and big quantity. E. coli BW25113 wild type strain, mutants with defects in hydrogen (H2) producing/oxidizing four hydrogenases (Hyd) (ΔhyaB ΔhybC, ΔhycE, ΔhyfG) and septuple mutant (ΔhyaB ΔhybC ΔhycA Δfd...
Escherichia coli perform mixed acid fermentation and produce hydrogen gas (H2) as one of the fermentation end products. E. coli can ferment sugars like glucose, xylose and alcohols like glycerol. It has been shown that E. coli has the ability to utilize pretreated organic waste (BSG or DG) or mixtures of it with glycerol and H2 can be produced. H2...
During mixed‐acid fermentation, Escherichia coli transports succinate mainly via transporters of the Dcu family. Here, we analyze the influence of Dcu transporters on hydrogenase (Hyd) and fermentative formate dehydrogenase (FDH‐H) activities and how this is affected by external pH and carbon source. Using selected dcu mutations, it was shown that...
Escherichia coli is able to ferment not only single but also mixtures of carbon sources. The formate metabolism and effect of formate on various enzymes have been extensively studied during sole glucose but not mixed carbon sources utilization. It was revealed that in membrane vesicles (MV) of wild type cells grown at pH 7.5 during fermentation of...
Growth properties, oxidation-reduction potential kinetics and hydrogen production of Escherichia coli BW25113 parental strain (PS) and hydrogenase (Hyd)-negative mutants were investigated after fermentative growth using office paper waste and cardboard (PW) hydrolysate (PWH). PWH was obtained by using dilute acid method in a steam sterilizer for 1...
Hydrogen (H2)-producing hydrogenase (Hyd) activity of E. coli wild type and mutants with defects in subunits of Hyd-3 or Hyd-4 during fermentation at different glucose concentrations and pHs was studied. Hyd-3 was mainly responsible for H2 production but a significant contribution by Hyd-4 to total H2 production depended on the glucose concentratio...
Escherichia coli has the ability to anaerobically utilize glucose, glycerol and mixtures of various sugars, alcohols and organic acids at different pH values. During fermentation fermentation end products are produced among them is hydrogen (Hz).Hzis produced via four reversible membrane_bound [Ni_Fe]_ hydrogenases (Hyd), which catalyze the reversi...
During fermentation FOF1 hydrolyzes ATP, coupling proton transport to proton-motive force (pmf) generation. Despite that, pmf generated by ATP hydrolysis does not satisfy the energy budget of a fermenting cell. However, pmf can also be generated by extrusion of weak organic acids such as lactate and by hydrogen cycling catalyzed by hydrogenases (Hy...
During fermentation Escherichia coli excrete succinate mainly via Dcu family carriers. Current work reveals the total and N,N’-dicyclohexylcarbodiimide (DCCD) inhibited ATPase activity at pH 7.5 and 5.5 in E. coli wild type and dcu mutants upon glycerol fermentation. The overall ATPase activity was highest at pH 7.5 in dcuABCD mutant. In wild type...
Escherichia coli wild type has the ability to utilize lactose or the mixture of lactose and glycerol producing bio-hydrogen (H 2 ) at different pH values. At pH 7.5 in hyaB (lacking large subunit of hydrogenase (Hyd)-1) and hybC (lacking large subunit of Hyd-2) single mutants fermenting lactose (1 g L ⁻¹ ) H 2 yield was ∼7- and 5-fold more, respect...
Escherichia coli encodes two formate channels, FocA and FocB, which either export formate or import it for further disproportionation by the formate hydrogenlyase (FHL) complex to H2 and CO2. We show that FocA/B appear to change their substrate-translocation direction depending on pH and electron donor. When cells were grown on glucose and glycerol...
It is known that Escherichia coli produces hydrogen gas (H2) during mixed acid fermentation via hydrogenase (Hyd) enzymes utilizing sugars, alcohols or organic acids. However, there are many sugars including lactose which are not studied well. Therefore, H2 production and responsible Hyd enzymes activity and role have been investigated. During lact...
During fermentation Escherichia coli produces di‐hydrogen (H2) via reversible membrane‐bound [Ni‐Fe]‐hydrogenases (Hyd). This study describes the total and N,N′‐dicyclohexylcarbodiimide (DCCD) inhibited ATPase activity and H2 production at various pHs in E. coli wild type and mutants encoding Hyd enzymes and formate dehydrogenases (FDH) on fermenta...
Microorganisms are part of the natural environments and reflect the effects of different physical factors of surrounding environment, such as gamma (γ) radiation. This work was devoted to the study of the influence of low doses of γ radiation with the intensity of 2.56 μW (m² s)⁻¹ (absorbed doses were 3.8 mGy for the radiation of 15 min and 7.2 mGy...
Hydrogen (H2) gas production in batch cultures was studied upon utilization of the mixture of glucose, glycerol and formic acid by Escherichia coli BW25113 wild type (wt) at pH of 5.5–7.5. At pH 7.5H2 was continuously produced during 240 h but at pH 6.5 and 5.5 it was detected till 168 h and 120 h, respectively. Specific growth rate (μ) of wt was t...
Brewery spent grains (BSG), one of the by-products of brewery production, were used for Escherichia coli growth and hydrogen (H2) production. The dilute acid and alkali pretreatment methods were used to hydrolyze the rough lignocellulose structure, and optimal conditions for the BSG hydrolysate (BSGH) preparation were developed. E. coli BW25113 wil...