scholarly journals Redox activity and H2 production upon glycerol fermentation in Escherichia coli: are hydrogenases reversible?

2009 ◽  
Vol 96 (3) ◽  
pp. 442a
Author(s):  
Karen Trchounian ◽  
Armen Trchounian
Keyword(s):  
Escherichia Coli ◽  
H2 Production ◽  
Redox Activity ◽  
Glycerol Fermentation

Escherichia coli hydrogenase activity and H2 production under glycerol fermentation at a low pH

2011 ◽  
Vol 36 (7) ◽  
pp. 4323-4331 ◽  
Author(s):  
Karen Trchounian ◽  
Viviana Sanchez-Torres ◽  
Thomas K. Wood ◽  
Armen Trchounian
Keyword(s):  
Escherichia Coli ◽  
H2 Production ◽  
Low Ph ◽  
Hydrogenase Activity ◽  
Glycerol Fermentation

ETHANOL SUPPLEMENTATION AS A NEW APPROACH TO REGULATE GROWTH AND HYDROGEN PRODUCTION OF $ \textit{ESCHERICHIA COLI} $ UPON GLYCEROL FERMENTATION

2020 ◽  
Vol 54 (2 (252)) ◽  
pp. 138-146
Author(s):  
A.A. Poladyan
Keyword(s):  
Escherichia Coli ◽  
Redox Potential ◽  
Bacterial Growth ◽  
H2 Production ◽  
Glycerol Fermentation ◽  
Medium Ph ◽  
New Approach ◽  
E Coli ◽  
Peptone Medium ◽  
By Products

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 in peptone medium, pH 7.5, were investigated upon various amounts of ethanol supplementation. In the presence of any amount of ethanol, but upon the absence of other sources of carbon, no H2 production was observed. Whereas ethanol (0.3 to 1 %) with a combination of glycerol stimulated both bacterial growth and H2 production, pH 7.5. A correlation was observed between the redox potential and stimulated by ethanol bacterial growth. The obtained results can be applied to regulate fermentation processes in biotechnology.

scholarly journals Fermentative Utilization of Glycerol by Escherichia coli and Its Implications for the Production of Fuels and Chemicals

2007 ◽  
Vol 74 (4) ◽  
pp. 1124-1135 ◽  
Author(s):  
Abhishek Murarka ◽  
Yandi Dharmadi ◽  
Syed Shams Yazdani ◽  
Ramon Gonzalez
Keyword(s):  
Escherichia Coli ◽  
Anaerobic Fermentation ◽  
Glycerol Metabolism ◽  
Nuclear Magnetic Resonance Analysis ◽  
Glycerol Fermentation ◽  
Glycerol Utilization ◽  
Negative Effect ◽  
Balance Analysis ◽  
Fuels And Chemicals ◽  
High Degree

ABSTRACT Availability, low prices, and a high degree of reduction make glycerol an ideal feedstock to produce reduced chemicals and fuels via anaerobic fermentation. Although glycerol metabolism in Escherichia coli had been thought to be restricted to respiratory conditions, we report here the utilization of this carbon source in the absence of electron acceptors. Cells grew fermentatively on glycerol and exhibited exponential growth at a maximum specific growth rate of 0.040 ± 0.003 h−1. The fermentative nature of glycerol metabolism was demonstrated through studies in which cell growth and glycerol utilization were observed despite blocking several respiratory processes. The incorporation of glycerol in cellular biomass was also investigated via nuclear magnetic resonance analysis of cultures in which either 50% U-13C-labeled or 100% unlabeled glycerol was used. These studies demonstrated that about 20% of the carbon incorporated into the protein fraction of biomass originated from glycerol. The use of U-13C-labeled glycerol also allowed the unambiguous identification of ethanol and succinic, acetic, and formic acids as the products of glycerol fermentation. The synthesis of ethanol was identified as a metabolic determinant of glycerol fermentation; this pathway fulfills energy requirements by generating, in a redox-balanced manner, 1 mol of ATP per mol of glycerol converted to ethanol. A fermentation balance analysis revealed an excellent closure of both carbon (∼95%) and redox (∼96%) balances. On the other hand, cultivation conditions that prevent H2 accumulation were shown to be an environmental determinant of glycerol fermentation. The negative effect of H2 is related to its metabolic recycling, which in turn generates an unfavorable internal redox state. The implications of our findings for the production of reduced chemicals and fuels were illustrated by coproducing ethanol plus formic acid and ethanol plus hydrogen from glycerol at yields approaching their theoretical maximum.

scholarly journals Roasted coffee wastes as a substrate for Escherichia coli to grow and produce hydrogen

2020 ◽  
Vol 367 (11) ◽  
Author(s):  
Hripsime Petrosyan ◽  
Liana Vanyan ◽  
Satenik Mirzoyan ◽  
Armen Trchounian ◽  
Karen Trchounian
Keyword(s):  
Escherichia Coli ◽  
H2 Production ◽  
High Rate ◽  
Main Role ◽  
Wild Type ◽  
Roasted Coffee ◽  
Energy Needs ◽  
Genetic Modifications ◽  
Coffee Grounds ◽  
And Control

ABSTRACT After brewing roasted coffee, spent coffee grounds (SCGs) are generated being one of the daily wastes emerging in dominant countries with high rate and big quantity. Escherichia 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 ΔfdoG ΔldhA ΔfrdC ΔaceE) were investigated by measuring change of external pH, bacterial growth and H2 production during the utilization of SCG hydrolysate. In wild type, H2 was produced with rate of 1.28 mL H2 (g sugar)−1 h−1 yielding 30.7 mL H2 (g sugar)−1 or 2.75 L (kg SCG)−1 during 24 h. In septuple mutant, H2 production yield was 72 mL H2 (g sugar)−1 with rate of 3 mL H2 (g sugar)−1 h−1. H2 generation was absent in hycE single mutant showing the main role of Hyd-3 in H2 production. During utilization of SCG wild type, specific growth rate was 0.72 ± 0.01 h−1 with biomass yield of 0.3 g L−1. Genetic modifications and control of external parameters during growth could lead to prolonged and enhanced microbiological H2 production by organic wastes, which will aid more efficiently global sustainable energy needs resulting in diversification of mobile and fixed energy sources.

Role of different Escherichia coli hydrogenases in H+ efflux and F1Fo-ATPase activity during glycerol fermentation at different pH values

2011 ◽  
Vol 31 (3) ◽  
pp. 179-184 ◽  
Author(s):  
Syuzanna Blbulyan ◽  
Arev Avagyan ◽  
Anna Poladyan ◽  
Armen Trchounian
Keyword(s):  
Escherichia Coli ◽  
Atpase Activity ◽  
Membrane Vesicle ◽  
Wild Type ◽  
Glucose Fermentation ◽  
Glycerol Fermentation ◽  
Whole Cells ◽  
Ph Values ◽  
F1fo Atpase

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 or Hyd-4) and was lowered in hyaB or hybC mutants (with defective Hyd-1 or Hyd-2) and hyaB hybC double mutant; DCCD (dicyclohexylcarbodi-imide)-sensitive H+ efflux was observed. At pH 5.5, H+ efflux in wild-type was lower compared with that at pH 7.5; it was increased in fhlA mutant and absent in hyaB hybC mutant. Membrane vesicle ATPase activity was lower in wild-type glycerol-fermented cells at pH 7.5 compared with that in glucose-fermented cells; 100 mM K+ did not stimulate ATPase activity. The latter at pH 7.5, compared with that in wild–type, was lower in hyaB and less in hybC mutants, stimulated in the hyaB hybC mutant and suppressed in the fhlA mutant; DCCD inhibited ATPase activity. At pH 5.5, the ATPase activities of hyaB and hybC mutants had similar values and were higher compared with that in wild-type; ATPase activity was suppressed in hyaB hybC and fhlA mutants. The results indicate that during glycerol fermentation, H+ was expelled also via F1Fo. At pH 7.5 Hyd-1 and Hyd-2 but not FhlA or Hyd-4 might be related to F1Fo or have their own H+-translocating ability. At pH 5.5, both Hyd-1 and Hyd-2 more than F1Fo might be involved in H+ efflux.

scholarly journals Construction of Direct Z-Scheme Photocatalyst by Mg1.2Ti1.8O5 and g-C3N4 Nanosheets toward Photocatalytic H2 Production and Disinfection

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Sijia Gu ◽  
Dan Zhang ◽  
Shirong Luo ◽  
Heng Yang
Keyword(s):  
Escherichia Coli ◽  
Photocatalytic Performance ◽  
Diffuse Reflectance Spectroscopy ◽  
Sol Gel ◽  
H2 Production ◽  
X Ray ◽  
E Coli ◽  
Carrier Separation ◽  
Positive Valence ◽  
Calcination Method

Exploring a novel and efficient photocatalyst is the key research goal to relieve energy and environmental issues. Herein, Z-scheme heterojunction composites were successfully fabricated by loading g-C3N4 nanosheets (CN) on the surface of Mg1.2Ti1.8O5 nanoflakes (MT) through a simple sol-gel method followed by the calcination method. The crystalline phase, morphologies, specific surface area, and optical and electrochemical performance of the samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-disperse X-ray spectroscopy (EDS), Brunauer-Emmett-Teller (BET), diffuse reflectance spectroscopy (DRS), and electrochemical measurements. Considering the suitable band structures of the components, the photocatalytic performance was evaluated by photocatalytic H2O splitting and photocatalytic inactivation of Escherichia coli (E. coli). Among the samples, MT/CN-10 (the molar percentage of melamine to as-obtained Mg-Ti gel was 10%) shows superior photocatalytic performance, which the average H2 production rate was 3.57 and 7.24 times higher than those of MT and CN alone. Additionally, the efficiency of inactivating Escherichia coli (E. coli) over MT/CN-10 was 1.95 and 2.06 times higher as compared to pure MT and CN, respectively. The enhancement of the photocatalytic performance was attributed to the advantages of the extremely negative conduction band (CB) of CN and the extremely positive valence band (VB) of MT, the enhanced light absorption, and more efficient photogenerated charge carrier separation.

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