Reoxidation Kinetics Research Articles

Investigation on YSZ- and SiO2-Doped Mn-Fe Oxide Granules Based on Drop Technique for Thermochemical Energy Storage.

The Mn-Fe oxide material possesses the advantages of abundant availability, low cost, and non-toxicity as an energy storage material, particularly addressing the limitation of sluggish reoxidation kinetics observed in pure manganese oxide. However, scaling up the thermal energy storage (TCES) system poses challenges to the stability of the reactivities and mechanical strength of materials over long-term cycles, necessitating their resolution. In this study, Mn-Fe granules were fabricated with a diameter of approximately 2 mm using the feasible and scalable drop technique, and the effects of Y2O3-stabilized ZrO2 (YSZ) and SiO2 doping, at various doping ratios ranging from 1-20 wt%, were investigated on both the anti-sintering behavior and mechanical strength. In a thermal gravimetric analyzer, the redox reaction tests showed that both the dopants led to an enhancement in the reoxidation rates when the doping ratios were in an appropriate range, while they also brought about a decrease in the reduction rate and energy storage density. In a packed-bed reactor, the results of five consecutive redox tests showed a similar pattern to that in a thermal gravimetric analyzer. Additionally, the doping led to the stable reduction/oxidation reaction rates during the cyclic tests. In the subsequent 120 cyclic tests, the Si-doped granules exhibited volume expansion with a decreased crushing strength, whereas the YSZ-doped granules experienced drastic shrinkage with an increase in the crushing strength. The 1 wt% Si and 2 wt% Si presented the best synthetic performance, which resulted from the milder sintering effects during the long-term cyclic tests.

Chemical expansion of La3+ and Yb3+ incorporated Zr-doped ceria ceramics for concentrated solar energy-driven thermochemical production of fuels

Redox studies on Zr, La, Yb doped ceria (Ce0.9M3+/4+0.1O2-x, M3+/4+ = Zr4+, La3+, Yb3+ and CeZr0.05 M3+0.05O1.95, M3+ = La3+, Yb3+) ceramics were performed using dilatometry and mass change measurements to analyze the chemical and thermal volume changes depending on reduction state which can have dramatic effects on the long-term stability of these ceramics in Concentrated Solar Energy (CSE)–driven applications relevant to the synthesis of fuels. The reduction extents determined by both methods under vacuum (p = 2×10−5 mbar) are similar up to 1673 K. At higher temperatures, CeO2, which has a higher vapor pressure than the oxides of the dopant ions, evaporates. As a result, there is an accumulation of doping ions, which leads to a porous surface zone. Surface enrichment of dopants, especially that of Zr4+, is crucial for re-oxidation kinetics. Co-doping with trivalent doping ions such as La3+ and Yb3+ reduces the extent of selective evaporation materializing it into a thinner porous surface layer. Trivalent dopants and their additional oxygen vacancies also influence the chemical expansion/contraction of the Zr4+ doped ceria crystal lattice during the redox reaction and thus lead to a reduction of mechanical stresses. We assume that additional oxygen vacancies from trivalent dopant ions promote the disordering of intrinsic oxygen vacancies, while smaller tetravalent ions such as Zr4+ compensates this effect. This explains that doped ceria with trivalent and tetravalent ions show almost the same chemical expansion as pure ceria. The new results on alteration, thermal and chemical expansions/contractions at high temperature are particularly important for the development of metal oxide ceramic components exposed to cyclic reducing and oxidizing atmospheres at elevated temperatures achieved via CSE.

Lead-free KNNLT piezoceramic multilayer actuators with Ni electrodes cofired under low oxygen partial pressure

The fabrication of piezoelectric multilayer actuators (MLA) with lead-free piezoceramic materials and excellent performance represents a great challenge in the process of replacing the current family of lead-based actuators. Sintering under low pO2 allows co-firing with base metal electrodes, which is an important step towards competitive multilayer actuator fabrication technologies. We prepared sodium potassium niobate (KNNLT) piezoelectric multilayer actuators with Ni electrodes by sintering at low pO2 of 10−11 atm at 950 °C, followed by reoxidation at 850 °C in 10−6 atm. We demonstrate the impact of the sintering protocol, i.e., sintering temperature Ts and pO2, on the phase composition and continuity of Ni electrodes, and on the actuator performance. We discuss the subtle interplay between sintering conditions, microstructure, reoxidation kinetics and piezoelectric performance. The Ni-MLA exhibits a unipolar strain of 0.74 ‰ at 3 kV/mm, a normalized strain coefficient d33* = 247 p.m./V and a loss of tanδ = 0.041.

Photosynthetic response mechanism to polybrominated diphenyl ether exposure in Chlorella pyrenoidosa

Polybrominated diphenyl ether (PBDE) contamination is common in aquatic environments and can severely damage aquatic organisms. However, there is a lack of information on the response and self-adaptation mechanisms of these organisms. Chlorella pyrenoidosa was treated with 2,2′,4,4′-tetrabromodiphenyl ether (BDE47), causing significant growth inhibition, pigment reduction, oxidative stress, and chloroplast atrophy. Photosynthetic damage contributed to inhibition, as indicated by Fv/Fm, Chl a fluorescence induction, photosynthetic oxygen evolution activity, and photosystem subunit stoichiometry. Here, Chl a fluorescence induction and quinone electron acceptor (QA−) reoxidation kinetics showed that the PSII donor and acceptor sides were insensitive to BDE47. Quantitative analyses of D1 and PsaD proteins illustrated that PSII and PSI complexes were the main primary targets of photosynthesis inhibition by BDE47. Significant modulation of PSII complex might have been caused by the potential binding of BDE47 on D1 protein, and molecular docking was performed to investigate this. Increased activation of antioxidant defense systems and photosystem repair as a function of exposure time indicated a positive resistance to BDE47. After a 5-day exposure, 23 % of BDE47 was metabolized. Our findings suggest that C. pyrenoidosa has potential as a bioremediator for wastewater-borne PBDEs and can improve our understanding of ecological risks to microalgae.

2-Hydroxychalcone as a Novel Natural Photosynthesis Inhibitor against Bloom-Forming Cyanobacteria.

The control of harmful cyanobacterial blooms has been becoming a global challenge. The development of eco-friendly algicides with strong specificity is urgently needed. The photosynthetic apparatus is a promising target site for algicides to minimize the possible harmful effects on animals and humans. In this study, biologically derived 2-hydroxychalcone efficiently inhibited the growth of bloom-forming M.aeruginosa by selectively interfering with photosynthesis. 2-Hydroxychalcone targeting Photosystem II (PSII) inhibited electron transfer between the primary and secondary electron acceptors (QA and QB) and the binding of plastoquinone (PQ) molecules to the QB binding pocket at the acceptor side of PSII, as revealed by polyphasic chlorophyll (Chl) a fluorescence induction and QA- reoxidation kinetics. Molecular docking for 2-hydroxychalcone to D1 protein and the proteomic responses of M.aeruginosa suggested that 2-hydroxychalcone formed a stable monodentate ligand with the nonheme iron in D1 protein, provoking significant modulation of PSII proteins. The unique binding mode of 2-hydroxychalcone with PSII differentiated it from classical PSII inhibitors. Furthermore, 2-hydroxychalcone down-regulated the expression of microcystin (MC) synthesis-related genes to restrain MC synthesis and release. These results indicated the potential application of 2-hydroxychalcone as an algicide or a template scaffold for designing novel derivatives with superior algicidal activity.

Diffusion from another perspective: Electric field complement to chemical diffusion analysis

Recently, Sinder et al. (2019) have studied the re-oxidation kinetics of chemically reduced, nitrogen-doped TiO2. Based on results of their ambipolar diffusion analysis, in this Comment, the associated electric field distribution and its evolution are studied. Numerical as well as approximate analytical solutions are given. It is found that the electric field profile exhibits a step-like shape penetrating from the specimen surface up to the ambipolar diffusion front. The ambipolar diffusion front pattern and its formation is discussed with special consideration of the impact of the internal electric field on the fluxes of the charged defects which are composed of counteracting diffusion-induced and field-driven contributions.

Electrochemical Reduction of O2 in Ca2+ -Containing DMSO: Role of Roughness and Single Crystal Structure.

In this study, the oxygen reduction reaction (ORR) in Ca2+‐containing dimethyl sulfoxide (DMSO) at well‐ordered and rough electrode surfaces is compared by using cyclic voltammetry, differential electrochemical mass spectrometry, rotating ring disk electrode, and atomic force microscopy measurements. Slightly soluble CaO2 is the main product during early ORR on gold electrodes; after completion of a monolayer of CaO and/or CaO2, which is formed in parallel and in competition to the peroxide, only superoxide is formed. When the monolayer is completely closed on smooth annealed Au, no further reduction occurs, whereas on rough Au a defect‐rich layer allows for continuous formation of superoxide. CaO2 formed either via two subsequent 1 e- transfer steps or by disproportionation of superoxide may be deposited on top of the CaO/CaO2 adsorbate layer. The slow dissolution of the peroxide particles is demonstrated by AFM. Whereas a smooth CaO/CaO2‐covered electrode shows severe deactivation and a CaO/CaO2‐covered rough electrode allows for diffusion‐limited superoxide formation, on single crystals peroxide formation is more pronounced. The reason is most likely the lack of nucleation sites for the blocking CaO/CaO2 layer. RRDE investigations showed sluggish reoxidation kinetics of the dissolved peroxide, which are most likely due to ion pairing with Ca2+. The apparent transfer coefficient is estimated by using variation of the electrode roughness, confirming the result of the usual Tafel analysis and indicating an equilibrated first 1 e- transfer.

A Quinol Anion as Catalytic Intermediate Coupling Proton Translocation With Electron Transfer in E. coli Respiratory Complex I.

Energy-converting NADH:ubiquinone oxidoreductase, respiratory complex I, plays a major role in cellular energy metabolism. It couples NADH oxidation and quinone reduction with the translocation of protons across the membrane, thus contributing to the protonmotive force. Complex I has an overall L-shaped structure with a peripheral arm catalyzing electron transfer and a membrane arm engaged in proton translocation. Although both reactions are arranged spatially separated, they are tightly coupled by a mechanism that is not fully understood. Using redox-difference UV-vis spectroscopy, an unknown redox component was identified in Escherichia coli complex I as reported earlier. A comparison of its spectrum with those obtained for different quinone species indicates features of a quinol anion. The re-oxidation kinetics of the quinol anion intermediate is significantly slower in the D213GH variant that was previously shown to operate with disturbed quinone chemistry. Addition of the quinone-site inhibitor piericidin A led to strongly decreased absorption peaks in the difference spectrum. A hypothesis for a mechanism of proton-coupled electron transfer with the quinol anion as catalytically important intermediate in complex I is discussed.

Effects of Monochromatic Illumination with LEDs Lights on the Growth and Photosynthetic Performance of Auxenochlorella protothecoides in Photo- and Mixotrophic Conditions.

This study examined the effects of monochromatic illumination (blue, red, green and yellow) employing light-emitting diodes (LEDs), trophic conditions (photoautotrophic and mixotrophic), and nitrogen availability (high and low peptone concentration) on the growth and biochemical composition of Auxenochlorella protothecoides. The results revealed that mixotrophic conditions did not favor A. protothecoides, giving lower growth rates compared to heterotrophy (dark conditions). However, mixotrophy gave significantly higher growth rates compared to photoautotrophy. The best light wavelengths for mixotrophic cultivation were that of white and red. In all cases investigated in this study, high peptone concentration (4 g/L) resulted in decreased growth rates. Regarding the biochemical composition of A. protothecoides, the strongest effect, irrespective of trophic conditions, was caused by nitrogen availability (peptone concentration). Specifically, at nitrogen replete conditions (4 g/L peptone), biomass was rich in proteins (32–67%), whereas under deplete conditions (0.5 g/L peptone), A. protothecoides accumulated mainly carbohydrates (up to 56%). Mixotrophic conditions generally favored higher carbohydrate content, whereas photoautotrophic conditions favored higher protein content. The different illumination spectra did not have any clear effect on the biochemical composition (metabolites content), except that, in all trophic conditions, the use of the green spectrum resulted in higher chlorophyll b content. Chlorophyll a fluorescence studies revealed that the trophic conditions and the high peptone concentrations impacted the photosystem II (PSII) performance, and also affected plastoquinone re-oxidation kinetics and the heterogeneity of the PSII reaction centers.

InVivo Reoxidation Kinetics of Free Thiols in Multiple Domains of IgG1 Antibodies in Rats.

While free thiols in monoclonal antibodies (mAbs) have been extensively characterized by invitro studies to probe its effect on antibody function and stability, their invivo biotransformation has not been comprehensively studied. In this study, a panel of five recombinant IgG1 mAbs with elevated free thiols in the VH, VL, and CH2 domains were intravenously administered into Wistar rats. Invivo biotransformation of thirty-five free thiol sites in total (7 disulfide pairs in VL, CL, VH, CH1, HH, CH2, CH3 domains across the 5 mAbs) were monitored using a denaturing differential isotopic tagging procedure on immunopurified timepoints followed by LC-MS of tryptic digests. The free thiol levels in two VH domain and one CH2 domain disulfide sites decreased invivo following first order kinetics. Free thiol levels of the remaining 32 sites were remarkably stable invivo. Further analytical characterization highlighted a positive association between a free thiol's solvent accessibility and a free thiol's reoxidation propensity. The data and discussion presented here shed valuable insights into the invivo fate of free thiols in several recombinant IgG1s and its implications for free thiols as a product quality attribute in therapeutic mAb products.

Solid‐State Reoxidation Kinetics of A/B‐Site Substituted LaMnO3 During Solar Thermochemical CO2 Conversion

Perovskite oxides exhibit noteworthy performance as efficient oxygen carriers for two‐step thermochemical conversion of CO2 using concentrated solar energy. Herein, the effect of composition on the solid‐state reoxidation kinetics of La0.5Sr0.5MnO3 and LaCo0.5Mn0.5O3 oxygen carriers is investigated. Thermochemical CO2 splitting reactions are conducted at several selected temperatures and a series of kinetic models are explored. Results indicate that the most suitable model describing the reoxidation mechanism depends on the oxygen carrier. A two‐step reaction mechanism is observed for La0.5Sr0.5MnO3 (first‐order model and 2D shrinking core model) depending on the extent of conversion whereas a diffusion controlled (3D‐Ginstling) mechanism is identified for LaCo0.5Mn0.5O3. The values of apparent activation energies (Ea) are remarkably low (≈5 kJ mol−1) and even negative, indicating an “anti‐Arrhenius” behavior. Pre‐exponential factors (A) are found to be low and influenced by the model used. Enthalpies of activation (ΔH‡ = −6 to −18 kJ mol−1) depend on the extent of conversion and composition, whereas entropies of activation (ΔS‡ = −0.33 kJ K−1 mol−1) remain constant. The observed discrepancies in the reoxidation mechanism can probably be attributed to thermal stability aspects, variations in lattice functionalities during the reaction, undesired side reactions, or a combination of these effects.

Toxic effects of potassium permanganate on photosystem II activity of cyanobacteria Microcystis aeruginosa

Effects of potassium permanganate (KMnO4) on PSII of Mycrocystis aeruginosa were investigated by measuring the chlorophyll fluorescence in vivo. KMnO4 exposure reduced the rate of oxygen evolution and cell growth. High concentration of KMnO4 (10 mg L-1) decreased the fast phase and increased the slow phase of QA- reoxidation kinetics. Electron transport after QA was blocked, resulting in a considerable amount of QA- reoxidation being performed via S2(QAQB)- charge recombination. KMnO4 decreased the density of the active photosynthetic reaction centers and the maximum quantum yield for primary photochemistry and inhibited electron transport, which resulted in a decline of the performance of PSII activity and caused an increase in dissipated energy flux per reaction center and antenna size. Our results suggest that both the donor side and the acceptor on the phase of QA- to QB to PQ of PSII in M. aeruginosa were targets of KMnO4 toxicity.

Chemical diffusion analysis of the oxidation kinetics of oxygen-deficient, nitrogen doped TiO2 thin films

Modification of TiO2 by nitrogen-doping improves its photocatalytic efficiency in visible-light activated photocatalytic processes. Therefore, the defect structure and the point defect transport of N-doped TiO2 represent important fundamental issues. Shi et al. (2012) have studied the re-oxidation kinetics of chemically reduced N-doped TiO2 (anatase) thin films by means of in situ optical spectroscopy. It was found that the time dependence of optical absorbance due to oxidation follows a parabolic rate law. The present paper is devoted to further development and refinement of the kinetic model. The ambipolar chemical diffusion model accounts for three types of mobile charged point defects with essentially different diffusion coefficients (electrons, holes, and titanium interstitials) as well as for a uniformly distributed background of immobile nitrogen ions. The concentration profiles of diffusing species and oxygen activity profiles have been obtained by numerical as well as by approximate analytical solutions of the chemical diffusion equation. The profiles reveal the presence of two separate singularities: an electron-hole recombination reaction front and a step-like electron concentration front whose coordinate obeys a parabolic rate law.

Isothermal Redox Kinetics of Co3O4-Fe2O3 Nano-Composite as a Thermochemical Heat Storage Material

Isothermal redox kinetics of as-received Co3O4 (AC), 1 h ball milled Co3O4 (BC), and 1 h ball milled Co3O4-15wt.% Fe2O3 (BCF) was investigated at various temperatures (1130, 1100, 1070, and 1040 °C for reduction and 830, 860, and 890°C for re-oxidation) by thermogravimetric method. It was found that mechanical activation with and without Fe2O3 addition decreases the rate of reduction in all isothermal reduction temperatures, while it improves the rate of re-oxidation in lower re-oxidation temperatures. Mechanical activation with and without Fe2O3 addition preserves and decreases the rate of re-oxidation at higher re-oxidation temperatures, respectively. In addition, according to the results, the re-oxidation kinetics was slower than reduction kinetics. A model-free method was used to calculate the redox activation energies. It was found that mechanical activation individually increases the reduction activation energy, while mechanical activation along with Fe2O3 addition decreases the reduction activation energy in comparison with as-received Co3O4. The results showed that reduction activation energies of AC, BC, and BCF samples varies depending on the reacted fraction (α) and are in the range of 140.6 – 166.6 kJ/mol, 175.5 – 213.7 kJ/mol and 111.5 – 121.3 kJ/mol, respectively. The results also showed that although both mechanical activations with and without Fe2O3 addition decreases the re-oxidation activation energy in comparison with as-received cobalt oxide, but the impact of mechanical activation without Fe2O3 addition on activation energy decline, is higher. Moreover, it was found that activation energies for the re-oxidation of AC, BC, and BCF samples are negative, variations depending on the reacted fraction (α), and are in the range of -76.8 to -133.5 kJ/mol, -440.2 to -471.9 kJ/mol, and -190.8 to -196.05 kJ/mol, respectively.

Syngas Production Through H2o/co2 Thermochemical Splitting

CO2 and H2O can be energy-upgraded through solar thermochemical cycles. Suitable redox materials are reduced in a solar reactor at high temperature (above 1300-1400°C) and afterwards re-oxidised by CO2 and/or H2O flow, thus producing CO and/or H2. Ceria was recognised as one of the most interesting materials for this process. However, high reduction temperature, low re-oxidation kinetics as well as low stability hindered its practical application. In this work, the redox properties of Ce0.75Zr0.25O2 system prepared by hydrothermal synthesis were compared with those of a co-precipitated sample with the same nominal composition used as reference. Samples were characterised by XRD and N2 physisorption; their self-reducibility and CO2 splitting activity were tested in a thermogravimetric balance, while H2O splitting properties were studied in an ad hoc fixed bed reactor on H2 pre-reduced samples. Obtained results proved that the material prepared by hydrothermal synthesis is characterised by both improved reducibility and splitting activity.

Improvement of splitting performance of Ce0.75Zr0.25O2 material: Tuning bulk and surface properties by hydrothermal synthesis

Thermochemical cycles received renewed interest as CO2 and H2O energy-upgrading processes using solar energy as source. The two-step cycles, based on self-reduction in a solar reactor at high temperature (above 1300–1400 °C) and re-oxidation by CO2 and/or H2O flow, are the most interesting due to their simplicity and high theoretical solar-to-fuel efficiency. In the two-step cycle, ceria has been recognized as the benchmark material but it suffers from high reduction temperature, low re-oxidation kinetics as well as low stability, thus hindering practical application. In this work, the redox properties of two Ce0.75Zr0.25O2 materials prepared by hydrothermal synthesis were compared with those of a co-precipitated sample with the same nominal composition used as reference. Samples were characterized by X-Ray Diffraction (XRD), N2 physisorption, Scanning Elecron Microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), and Electron Paramagnetic Resonance (EPR); their self-reducibility and CO2 splitting activity were tested in a Thermogravimetric (TG) balance, while H2O splitting properties were studied in an ad-hoc fixed bed reactor on H2 pre-reduced samples. Characterization results and activity tests agreed that the Ce3+ fraction both on the surface and in the bulk of ceria-zirconia can be increased by hydrothermal synthesis, thus providing improved redox properties and higher splitting activity with respect to the co-precipitated sample. So, hydrothermal synthesis, providing a controlled nucleation and growth of crystallites, appears as a promising route for the preparation of ceria-based materials with tuned oxygen vacancies.

Insights into the redox kinetics of vanadium substituted heteropoly acids through liquid core waveguide membrane microreactor studies

A liquid core waveguide membrane microreactor is a novel concept that allows in situ spectroscopy to be carried out in an optical microreactor, while enabling a very high gas-to-liquid mass transfer. The potential of this reactor concept to derive kinetics in gas/liquid reactions is demonstrated using the heteropoly acids catalyzed oxidation of biomass to formic acid (the ‘OxFA process’). For vanadium-substituted, Keggin-type heteropoly acids, the kinetics of the reduction and reoxidation step of the catalyst cycle was deduced using in situ UV/Vis spectroscopy. Reduction was studied from 40 to 80 °C: a strong dependency of the reduction kinetics was deduced. In combination with additional cyclic voltammetry and EPR characterization, it can be assumed that two active centers promote this reaction, while the existence and proportions of both types depends on the degree of vanadium substitution. The rapid mass transfer allowed transient response experiments to be carried out for the reoxidation step, which was studied up to 150 °C. Switching from anaerobic to aerobic conditions, an even stronger dependency of the reoxidation kinetics on the degree of vanadium substitution was revealed.

An investigation on the redox kinetics of NH3-SCR over a V/Mo/Ti catalyst: Evidence of a direct role of NO in the re-oxidation step

This study addresses a kinetic investigation of NH3-SCR on commercial SCR catalysts with composition V2O5/MoO3/TiO2. Objective of the study is an improved kinetic description of the reaction, based on the recognition of the redox nature of the V-site; which calls for an understanding of the effect of O2.At this scope, an extensive experimental investigation over a powdered catalyst was performed at largely varying concentrations of O2 (from 0.06 to 8%) both at high and at low NO and NH3 concentration. It was found that the increase of the O2 feed content promoted NO conversion with asymptotic trend: the promotion was important in the range 0.06–3%, but became moderate in the range 3–8%. Unexpectedly, the effect of O2 was equally important at high NO and NH3 concentration as well as at low NO and NH3 concentration (where a kinetic control from the reduction step and thus a negligible role of the oxidation step were expected). The kinetic analysis revealed that the observed experimental trends can be described by a Mars-van Krevelen rate expression assuming that the rate of re-oxidation depends on NO concentration as well as the rate of reduction does. A molecular rate equation which incorporates a simple linear dependence on NO concentration in the re-oxidation kinetics fully describes the whole bulk of data and is suitable to engineering purposes. The existence of an NH3 inhibiting effect was also included. The global rate expression was successfully validated against independent pilot-scale experiments on slabs.

The chloroplast 2-cysteine peroxiredoxin functions as thioredoxin oxidase in redox regulation of chloroplast metabolism.

Thiol-dependent redox regulation controls central processes in plant cells including photosynthesis. Thioredoxins reductively activate, for example, Calvin-Benson cycle enzymes. However, the mechanism of oxidative inactivation is unknown despite its importance for efficient regulation. Here, the abundant 2-cysteine peroxiredoxin (2-CysPrx), but not its site-directed variants, mediates rapid inactivation of reductively activated fructose-1,6-bisphosphatase and NADPH-dependent malate dehydrogenase (MDH) in the presence of the proper thioredoxins. Deactivation of phosphoribulokinase (PRK) and MDH was compromised in 2cysprxAB mutant plants upon light/dark transition compared to wildtype. The decisive role of 2-CysPrx in regulating photosynthesis was evident from reoxidation kinetics of ferredoxin upon darkening of intact leaves since its half time decreased 3.5-times in 2cysprxAB. The disadvantage of inefficient deactivation turned into an advantage in fluctuating light. Physiological parameters like MDH and PRK inactivation, photosynthetic kinetics and response to fluctuating light fully recovered in 2cysprxAB mutants complemented with 2-CysPrxA underlining the significance of 2-CysPrx. The results show that the 2-CysPrx serves as electron sink in the thiol network important to oxidize reductively activated proteins and represents the missing link in the reversal of thioredoxin-dependent regulation.

Chlorophyll fluorescence induction and relaxation system for the continuous monitoring of photosynthetic capacity in photobioreactors.

The development of high-performance photobioreactors equipped with automatic systems for non-invasive real-time monitoring of cultivation conditions and photosynthetic parameters is a challenge in algae biotechnology. Therefore, we developed a chlorophyll (Chl) fluorescence measuring system for the online recording of the light-induced fluorescence rise and the dark relaxation of the flash-induced fluorescence yield (Qa- - re-oxidation kinetics) in photobioreactors. This system provides automatic measurements in a broad range of Chl concentrations at high frequency of gas-tight sampling, and advanced data analysis. The performance of this new technique was tested on the green microalgae Chlamydomonas reinhardtii subjected to a sulfur deficiency stress and to long-term dark anaerobic conditions. More than thousand fluorescence kinetic curves were recorded and analyzed during aerobic and anaerobic stages of incubation. Lifetime and amplitude values of kinetic components were determined, and their dynamics plotted on heatmaps. Out of these data, stress-sensitive kinetic parameters were specified. This implemented apparatus can therefore be useful for the continuous real-time monitoring of algal photosynthesis in photobioreactors.