Anna Poladyan

• PhD
• Professor (Associate) at Yerevan State University

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...

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...

The redox homeostasis is a state of balance between the formation and utilization of Reactive Oxygen and/or Nitrogen Species, endogenous antioxidant defense systems, and exogenous dietary antioxidants. The disturbance of redox homeostasis may increase the risk of development of different deviations. The solution seems to be either the increase...

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...

The processes of lipid peroxidation (LPO) were studied in rat brain and liver tissues under normal conditions, as well as under conditions of hypobaric hypoxia, since it is known that hypoxia causes the development of LPO in the cells of organism tissues. It has been also studied the influense of dry flowers of Trifolium pratense L. (red clover) an...

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.

How the utilization of dairy industry organic waste materials by microbes efficiently support the economic generation of both bacterial biomass and biotechnologically relevant Hyde.

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 (...

The Hydrogenases (Hyd) of chemolithoautotrophic Ralstonia eutropha H16 are attractive biocatalysts for operation of enzymatic fuel cell (EFC). The expression of O 2 tolerant Hyds was stated under energy limited conditions or in presence of gas mixtures (H 2 , O 2 , CO 2) and during bacterial heterotrophic growth [1]. It was shown, that the suppleme...

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...

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...

Molecular hydrogen (H2) and ethanol are the main by-products of glycerol fermentation by Escherichia coli. In this study, the growth of E. coli BW25113 was investigated with the addition of small amounts (0.05 to 2 %) of ethanol alone and in a combination with glycerol The bacterial growth, the kinetic of the redox potential, and the H2 production...

Glycerol is an organic waste material, which can be used for production of microbial biomass and consequently serving valuable biocatalysts promoting generation of electric current in microbial fuel cell (MFC). [NiFe]-Hydrogenases (Hyd) of Escherichia coli and Ralstonia eutropha may be applied as potential anode biocatalysts in MFC. In this study,...

Xylose, one of the most common sugars derived from lignocellulosic material, can be fermented by bacteria. Escherichia coli uses natural sugars to produce biomass and H2. The latter can be formed from the formate via formate hydrolysis (FHL) during the fermentation of xylose or glucose; [Ni-Fe]-hydrogenase (Hyd) is involved in H2 formation. The gro...

Background: The chemolithoautotrophic β-proteobacterium Ralstonia eutropha H16 (Cupriavidus necator) is one of the most studied model organisms for growth on H2 and CO2. R. eutropha H16 is also a biologically significant bacterium capable of synthesizing O2-tolerant [NiFe]-hydrogenases (Hyds), which can be used as anode biocatalysts in enzyme fuel...

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...

Background: Ralstoniq eutropha is able to grow on organic substrates or on H2/CO2 under aerobic conditions. For lithoautotrophic growth on H2, CO2, 02, R. eutropha employs O2-tolerent [NiFe]-hydrogenases (Hyds), involved in H2 turnover. Hyds of R. eutropha are promising candidate enzymes for H2-based biofuel applications. Consumption of cheap waste...

Background: Molecular hydrogen (H2) is one of the best candidates, as a renewable energy carrier, and it is expected to play an important role in the construction ofa sustainable energy economy. Hydrogenases (Hyd) are responsible for oxidation and/or reduction of H2; they can serye as valuable biocatalysts and generate a large amount of electric cu...

In this study, the new strategy for long term bio-hydrogen (H2) production using different substrates and waste materials is presented. Growth characteristics and H2 production were investigated upon consumption of 0.4% xylose and 1% glycerol alone (which were optimal) or their mixture by Escherichia coli BW25113 wild type parental strain (PS) and...

Glycerol as a waste material of biodiesel and other industries can be considered for biological hydrogen (H2) production. Upon Escherichia coli glycerol fermentation formate, ethanol and etc. are produced. Formate decomposition by fromatehydrogenaselyase enzymes lead to H2 and CO2 formation. Four [NiFe] Hydrogenase (Hyd) enzymes are involved in thi...

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...

The Escherichia coli BW25113 or MC4100 wild type parental strains growth and H2 production kinetics was studied in batch cultures of minimal salt medium (MSM) and peptone medium (PM) at pH of 5.5-7.5 upon glycerol (10 g L⁻¹) fermentation and formate (0.68 g L⁻¹) supplementation. The role of formate alone or with glycerol on growth and H2 production...

Molecular hydrogen (H) is e៧í°†cient, ecologically friendly and renewable energy source for the future. Organic wastes utilization for H production provides inexpensive energy generation with simultaneous waste treatment. Beer is one of the most consumed beverages over the world, consequently during it's manufacture various by-products in huge amou...

Escherichia coli growth and H2 production were followed in the presence of heavy metal ions and their mixtures during glycerol or glucose fermentation at pH 5.5–7.5. Ni²⁺ (50 μM) with Fe²⁺ (50 μM) but not sole metals stimulated bacterial biomass during glycerol fermentation at pH 6.5. Ni²⁺+Fe³⁺ (50 μM), Ni² +Fe³⁺+Mo⁶⁺ (20 μM) and Fe³⁺+Mo⁶⁺ (20 μM)...

Hydrogen (H2) is well-known effective, ecologically clean and renewable fuel. Bacterial H2 production is a promising one and its use in industrial level is expected to increase in the nearest future to establish sustainable and renewable energy source. Escherichia coli wild type BW25113 growth yield was shown to be stimulated 1.3–1.5-fold by nickel...

Herbal medicine requires searching for new sources with antimicrobial activity. Alkanna sp. (Boraginaceae) is widely used in medicine due to detoxification and antibacterial effects. The aim of this study was to obtain Alkanna orientalis (L.) Boiss. plant callus extracts, to investigate antimicrobial activity of extracts against bacteria and yeast...

Escherichia coli possesses four [Ni-Fe]-hydrogenase (Hyd) enzymes, encoded by the hya, hyb, hyc and hyf operons and which are responsible for H2 production under different conditions. The influence of formate alone or mixed with glycerol on growth of E. coli wild type and Hyd mutants with deletions of key subunits of Hyd 1-4, respectively, and H2 p...

Changes in oxidation–reduction potential (ORP) values during Escherichia coli ΔhyaB ΔhybC double mutant lacking of large subunits of hydrogenases 1 (Hyd-1) and 2 (Hyd-2) and effects of redox reagents were studied upon glucose fermentation at acidic (5.5) and alkaline (7.5) pHs. H2 production yield was determined by the readings of platinum and tita...

Geobacillus toebii ArzA-8, from Armenian geothermal springs, grew well in nutrient broth. During its growth, changes in pH in opposite directions were observed depending on glucose supplementation. Accordingly, the decrease in the redox potential was determined using titanium-silicate (Eh) and platinum (Eh') electrodes: Eh decreased to -150±3mV and...

Simultaneous measurement of redox potential (Eh ) and determination of H2 evolution kinetics using a pair of titanium-silicate and platinum redox electrodes in fermenting cultures of Escherichia coli wild type and different mutants lacking hydrogenases 1 (Hyd-1) or 2 (Hyd-2) revealed that Hyd-1 controls the onset of H2 evolution at slightly alkalin...

Glycerol fermentation redox routes by E. coli wild type batch cultures and effects of Ni2+, Fe2+ and Fe3+ ions of different concentration (0.01–0.3 mM) on cell growth and H2 production were investigated. Influences of aforementioned metal ions and Cu2+, as well as Fe2+ on H2 production rate in vitro assays were also studied in wild type and hyaB hy...

Glycerol and glucose fermentation redox routes by Escherichia coli and their regulation by oxidizing and reducing reagents were investigated at different pHs. Cell growth was followed by decrease of pH and redox potential (E h ). During glycerol utilization at pH 7.5 ∆pH, the difference between initial and end pH, was lower compared with glucose fe...

Molecular hydrogen (H(2)) can be produced via hydrogenases during mixed-acid fermentation by bacteria. Escherichia coli possesses multiple (four) hydrogenases. Hydrogenase 3 (Hyd-3) and probably 4 (Hyd-4) with formate dehydrogenase H (Fdh-H) form two different H(2)-evolving formate hydrogen lyase (FHL) pathways during glucose fermentation. For both...

The transport of protons and potassium ions across the membranes of the bacteria Enterococcus hirae growing in an alkaline medium (pH 8.0) or under experimental conditions (pH 7.5) during glucose fermentation accomplished by a KtrI system of absorption of potassium ions, which can interact with F0F1-ATPase to form at H+-K+-pump, has been studied. I...

Escherichia coli is able to ferment glycerol and produce H2 by different Hyds (hydrogenases). Wild-type whole cells were shown to extrude H+ through the F1Fo-ATPase and by other means with a lower rate compared with that under glucose fermentation. At pH 7.5, H+ efflux was stimulated in fhlA mutant (with defective transcriptional activator of Hyd-3...

Production of molecular hydrogen (H2) by bacteria from a variety of renewable, cheap and abundant carbon sources is a developing new area of technology. Recently it has been shown that bacteria Escherichia coli is able to ferment glycerol and produce H2 via formate hydrogen lyase (FHL) system probably (1). It was demonstrated that in E. coli during...

Escherichia coli, grown under anaerobic conditions in acidic medium (pH 5.5), upon hyperosmotic stress accumulates pota.ssium ions mainly through the Kup system, functioning of which is related to a proton efflux decrease. It was shown that H+ secretion but not K+ uptake induced by glucose addition was inhibited by N,N'-dicyclohexylcarbodiimide (DC...

Escherichia coli grown under anaerobic conditions in acidic medium (pH 5.5) upon hyperosmotic stress accumulates potassium ions mainly through the Kup system, the functioning of which is associated with proton efflux decrease. It was shown that H+ secretion but not glucose-induced K+ uptake was inhibited by N,N′-dicyclohexylcarbodiimide (DCC). The...

It was found that modification of thiol (SH-) groups of membrane proteins by Ellman’s reagent (5,5′-dithiol-bis-(2-nitrobenzoic) acid) results in inhibition of proton efflux and K+ influx in anaerobically grown (pH 7.5) wild-type strains of Escherichia coli and causes disturbances in K+-dependent, N,N′-dicyclohexylcarbodiimide-sensitive ATPase acti...

It was found that modification of thiol (SH-) groups of membrane proteins by Ellman’s reagent (5,5′-dithiol-bis-(2-nitrobenzoic) acid) results in inhibition of proton efflux and K+ influx in anaerobically grown (pH 7.5) wild-type strains of Escherichia coli and causes disturbances in K+-dependent, N,N′-dicyclohexylcarbodiimide-sensitive ATPase acti...

A correlation between the rate of ATP synthesis by F0F1 ATP synthase and formate oxidation by formate hydrogen lyase (FHL) has been found in inside-out membrane vesicles of the Escherichia coli mutant JW 136 (Δhya/Δhyb) with double deletions of hydrogenases 1 and 2, grown anaerobically on glucose in the absence of external electron acceptors at pH...

A correlation between the rate of ATP synthesis by F0F1 ATP-synthase and formate oxidation by formate hydrogen lyase (FHL) has been established in inverted membrane vesicles of Escherichia coli JW 136 mutant with double deletions (delta hya/ delta hyb) of hydrogenase 1 and 2 grown anaerobically on glucose in the absence of external electron accepto...

Enterococcus hirae ATCC 9790 are able to grow under anaerobic conditions during the fermentation of sugars (pH 8.0) in the presence of the protonophore carbonylcyanide-m-chlorophenylhydrazone at a lesser specific growth rate. As bacteria grow, the acidification of the external medium and a drop in the redox potential from positive to negative (up t...

The number of accessible SH groups was determined in membrane vesicles prepared from Enterococcus hirae grown under anaerobic conditions at alkaline pH (pH 8.0). Addition of ATP or nicotinamide adenine dinucleotides (NAD(+) +NADH) to the vesicles caused a approximately 4-fold or approximately 1.9-fold increase in the number of SH-groups, respective...

The bacterium Enterococcus hirae is able to grow under anaerobic conditions during sugar fermentation (pH 8.0) in the presence of the protonophore carbonyl cyanide m-chlorophenylhydrazone at a considerably lower specific rate. Bacterial growth was accompanied by acidification of the medium and a drop in its redox potential from positive to negative...

The number of accessible SH-groups was determined in membrane vesicles prepared from Escherichia coli growing in fermentation conditions at slightly alkaline pH on glucose with or without added formate. Addition of ATP or formate to the vesicles caused a approximately 1.4-fold increase in the number of accessible SH-groups. The increase was inhibit...

The hyc operon of Escherichia coli encodes the H2-evolving hydrogenase 3 (Hyd-3) complex that, in conjunction with formate dehydrogenase H (Fdh-H), constitutes a membrane-associated formate hydrogenlyase (FHL) catalyzing the disproportionation of formate to CO2 and H2 during fermentative growth at low pH. Recently, an operon (hyf) encoding a potent...

To study the effect of diethylsulphoxide (DESO) on Escherichia coli growth, survival and ionic exchange in comparison with dimethylsulphoxide (DMSO). Bacterial survival was estimated by counting colony-forming units and by the most probable number (five-tube) technique; the K+ and H+ transport and H(2) formation were determined electrochemically. D...

Anaerobically grown glucose-fermenting E. coli cells produce molecular hydrogen, acidify the medium and uptake potassium ions. It was shown that the H2 release and the proton-potassium exchange with the fixed (2H+/K+) stoichiometry of the initial DCC-sensitive fluxes were lost in mutants with the deleted fdhF gene or the hycA-H operon responsible f...

It is shown that Enterococcus hirae grown in a trypton medium at high alkaline pH (initial pH value 9.5), when being transferred to a medium containing an energy source (glucose) and moderate K+ concentration with pH 8.5, carry out H+-K+ exchahnge, which is inhibited by N,N'-dicyclohexylcarbodiimide. The KM value for K+ uptake is 2.2 mM; the stoich...