scholarly journals Growth of the facultative chemolithoautotroph Ralstonia eutropha on organic waste materials: growth characteristics, redox regulation and hydrogenase activity

2019 ◽  
Vol 18 (1) ◽  
Author(s):  
Anna Poladyan ◽  
Syuzanna Blbulyan ◽  
Mayramik Sahakyan ◽  
Oliver Lenz ◽  
Armen Trchounian
Keyword(s):  
Fuel Cells ◽  
Redox Regulation ◽  
Ralstonia Eutropha ◽  
Membrane Vesicles ◽  
Dry Weight ◽  
Negative Influence ◽  
Model Organisms ◽  
Hydrogenase Activity ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential

Abstract 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 cells. For heterotrophic growth of R. eutropha, various sources of organic carbon and energy can be used. Results Growth, bioenergetic properties, and oxidation–reduction potential (ORP) kinetics were investigated during cultivation of R. eutropha H16 on fructose and glycerol or lignocellulose-containing brewery spent grain hydrolysate (BSGH). BSGH was used as carbon and energy source by R. eutropha H16, and the activities of the membrane-bound hydrogenase (MBH) and cytoplasmic, soluble hydrogenase (SH) were measured in different growth phases. Growth of R. eutropha H16 on optimized BSGH medium yielded ~ 0.7 g cell dry weight L−1 with 3.50 ± 0.02 (SH) and 2.3 ± 0.03 (MBH) U (mg protein)−1 activities. Upon growth on fructose and glycerol, a pH drop from 7.0 to 6.7 and a concomitant decrease of ORP was observed. During growth on BSGH, in contrast, the pH and ORP stayed constant. The growth rate was slightly stimulated through addition of 1 mM K3[Fe(CN)6], whereas temporarily reduced growth was observed upon addition of 3 mM dithiothreitol. The overall and N,N′-dicyclohexylcarbodiimide-sensitive ATPase activities of membrane vesicles were ~ 4- and ~ 2.5-fold lower, respectively, upon growth on fructose and glycerol (FGN) compared with only fructose utilization (FN). Compared to FN, ORP was lower upon bacterial growth on FGN, GFN, and BSGH. Conclusions Our results suggest that reductive conditions and low ATPase activity might be signals for energy depletion, which, in turn, leads to increased hydrogenase biosynthesis to overcome this unfavorable situation. Addition of fructose or microelements have no, or a negative, influence on hydrogenase activity. Organic wastes (glycerol, BSGH) are promising carbon and energy sources for the formation of biomass harboring significant amounts of the biotechnologically relevant hydrogenases MBH and SH. The results are valuable for using microbial cells as producers of hydrogenase enzymes as catalysts in enzymatic fuel cells.

scholarly journals HYDROCHEMICAL CHARACTERIZATION OF URBAN SPRING WATERS FROM TIJUCO STREAM, SUB-BASIN OF RIBEIRÃO DO ONÇA, CENTRAL-NORTH REGION OF BELO HORIZONTE

2018 ◽  
Vol 15 (30) ◽  
pp. 210-220
Author(s):  
A. C. O. PELAES ◽  
S. A. BONFIM ◽  
H. E. L. PALMIERI ◽  
L. M. L. A. AULER ◽  
M. J. S. F. SILVA
Keyword(s):  
Previous Treatment ◽  
Dry Weight ◽  
Human Consumption ◽  
Temperature Conductivity ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Calcium Bicarbonate ◽  
Belo Horizonte ◽  
Good Agreement

This work focuses on drawing up the hydrochemical profile of water samples collected in five springs of the Tijuco stream. The evaluation was based on quantification of the elements Al, As, Ba, Be, B, Ca, Cd, Co, Cr, Li, Pb, Cu, Fe, Mg, Mn, Mo, Ni, Se, Si, Sb, U, V, and Zn; the anions F-, Cl-, NO2-, NO3-, SO42-; the cations Na+, NH4+, K+ and the parameters: turbidity, temperature, conductivity, total dissolved solids, oxidation-reduction potential, pH and dissolved oxygen. Alkalinity, hardness, Cr(VI) and dry weight (180 °C) were also quantified. The analyzed parameters were compared with the Maximum Values (VMP) established by the resolutions nº 396/2008 of CONAMA and nº 2.914/2011 of the Ministry of Health. Most of the parameters presented a good agreement with the VMP, however, due to the parameters turbidity, pH, nitrate, and manganese exceed the VMP in some samples, these waters can only be used for human consumption after previous treatment. However, they can be used in animal watering, irrigation and recreation. The waters were classified into three groups: calcium-bicarbonate, sodium-bicarbonate and mixed-bicarbonate.

scholarly journals In situ measurements of oxidation–reduction potential and hydrogen peroxide concentration as tools for revealing LPMO inactivation during enzymatic saccharification of cellulose

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Adnan Kadić ◽  
Anikó Várnai ◽  
Vincent G. H. Eijsink ◽  
Svein Jarle Horn ◽  
Gunnar Lidén
Keyword(s):  
Reduction Potential ◽  
Enzymatic Saccharification ◽  
The State ◽  
Enzyme Inactivation ◽  
Ex Situ ◽  
Process Economics ◽  
Complete Inactivation ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential

Abstract Background Biochemical conversion of lignocellulosic biomass to simple sugars at commercial scale is hampered by the high cost of saccharifying enzymes. Lytic polysaccharide monooxygenases (LPMOs) may hold the key to overcome economic barriers. Recent studies have shown that controlled activation of LPMOs by a continuous H2O2 supply can boost saccharification yields, while overdosing H2O2 may lead to enzyme inactivation and reduce overall sugar yields. While following LPMO action by ex situ analysis of LPMO products confirms enzyme inactivation, currently no preventive measures are available to intervene before complete inactivation. Results Here, we carried out enzymatic saccharification of the model cellulose Avicel with an LPMO-containing enzyme preparation (Cellic CTec3) and H2O2 feed at 1 L bioreactor scale and followed the oxidation–reduction potential and H2O2 concentration in situ with corresponding electrode probes. The rate of oxidation of the reductant as well as the estimation of the amount of H2O2 consumed by LPMOs indicate that, in addition to oxidative depolymerization of cellulose, LPMOs consume H2O2 in a futile non-catalytic cycle, and that inactivation of LPMOs happens gradually and starts long before the accumulation of LPMO-generated oxidative products comes to a halt. Conclusion Our results indicate that, in this model system, the collapse of the LPMO-catalyzed reaction may be predicted by the rate of oxidation of the reductant, the accumulation of H2O2 in the reactor or, indirectly, by a clear increase in the oxidation–reduction potential. Being able to monitor the state of the LPMO activity in situ may help maximizing the benefit of LPMO action during saccharification. Overcoming enzyme inactivation could allow improving overall saccharification yields beyond the state of the art while lowering LPMO and, potentially, cellulase loads, both of which would have beneficial consequences on process economics.

scholarly journals The Negative Impact of Varicocele on Basic Semen Parameters, Sperm Nuclear DNA Dispersion and Oxidation-Reduction Potential in Semen

2021 ◽  
Vol 18 (11) ◽  
pp. 5977
Author(s):  
Kamil Gill ◽  
Michal Kups ◽  
Patryk Harasny ◽  
Tomasz Machalowski ◽  
Marta Grabowska ◽  
...  
Keyword(s):  
Reduction Potential ◽  
Nuclear Dna ◽  
Study Groups ◽  
Semen Parameters ◽  
Sperm Dna Fragmentation ◽  
Control Groups ◽  
Infertile Men ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Sperm Dna

Since varicocele is so common in infertile men, this study intends to analyse the relationships between varicocele and conventional semen characteristics, sperm nuclear DNA dispersion and oxidation-reduction potential (ORP) in semen. Varicocele-positive and varicocele-negative infertile men (study groups) showed significantly lower standard sperm parameters and higher sperm DNA fragmentation (SDF) and ORP in semen than healthy volunteers and subjects with proven fertility (control groups). A lower proportion of low SDF levels (0–15% SDF) and higher incidence of high SDF levels (>30% SDF), as well as a higher prevalence of high ORP values (>1.37 mV/106 sperm/mL), were found in the study groups vs. the control groups. Moreover, infertile men had significantly lower odds ratios (ORs) for low SDF levels and significantly higher ORs for high SDF levels and high ORP. SDF and ORP were negatively correlated with sperm number, morphology, motility and vitality. Furthermore, a significant positive correlation was found between SDF and ORP. The obtained results suggest that disorders of spermatogenesis may occur in varicocele-related infertility. These abnormalities are manifested not only by reduced standard semen parameters but also by decreased sperm DNA integrity and simultaneously increased oxidative stress in semen.

Derivation of Optimum Study Factors for Samples Contaminated with Cd Using Electric/Magnetic Field and ORP

2013 ◽  
Vol 813 ◽  
pp. 519-524
Author(s):  
Sang An Ha ◽  
Jei Pil Wang
Keyword(s):  
Magnetic Field ◽  
Heavy Metals ◽  
Removal Rate ◽  
Underground Water ◽  
Liquid Electrode ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Removal Of Heavy Metals ◽  
High Removal Rate ◽  
Membrane Treatment

A purpose of the present study is to derive optimum study factors for removal of heavy metals using combined alternating current electric/magnetic field and electric membranes for the area contaminated with heavy metals in soil or underground water. ORP (Oxidation Reduction Potential) analysis was conducted to determine an intensity of tendency for oxidation or reduction of the samples contaminated with heavy metals, and electrical membrane treatment was used with adjustment of concentrations and voltages of liquid electrode (Na2SO4) to derive a high removal rate. Removal constants were analyzed to be 0.0417, 0.119, 0.1594 when the voltages were 5V, 10V, 15V, respectively, and treatment efficiency was shown to increase as the liquid electrode concentration was increased. Keywords: heavy metals, electric/magnetic field, ORP, electrical membrane

scholarly journals The influence of oxidation-reduction state on the kinetic stability of pig kidney general acyl-CoA dehydrogenase and other flavoproteins

1984 ◽  
Vol 224 (2) ◽  
pp. 577-580 ◽  
Author(s):  
M Madden ◽  
S M Lau ◽  
C Thorpe
Keyword(s):  
Reduction Potential ◽  
Binding Protein ◽  
Sodium Dithionite ◽  
Egg White ◽  
Kinetic Stability ◽  
Pig Kidney ◽  
Data Support ◽  
Oxidation Reduction ◽  
Oxidation Reduction Potential ◽  
Electron Transferring Flavoprotein

Pig kidney general acyl-CoA dehydrogenase is markedly stabilized against loss of flavin and activity in 7.3 M-urea or at 60 degrees C upon reduction with sodium dithionite or octanoyl-CoA. Electron transferring flavoprotein is similarly stabilized, whereas egg white riboflavin-binding protein loses flavin more readily on reduction. These and other data support the anticipated correlation between the kinetic stability of the holoproteins and the oxidation-reduction potential of their bound flavins.

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