An effective visible-light driven fumarate production from gaseous CO2 and pyruvate by the cationic zinc porphyrin-based photocatalytic system with dual biocatalysts.

Fumaric acid is a useful unsaturated dicarboxylic acid that serves as a precursor for the biodegradable plastics poly(butylene succinate) and poly(propylene fumarate). Currently, fumaric acid is mainly synthesised from petroleum resources such as benzene. It is therefore desirable to develop methods to produce fumaric acid from renewable resources such as those derived from biomass. In this work, an effective visible-light driven fumarate production from gaseous CO2 and pyruvate with the system consisting of triethanolamine, cationic water-soluble zinc porphyrin, zinc tetrakis(4-N,N,N-trimethylaminophenyl)porphyrin, pentamethylcyclopentadienyl coordinated rhodium(III) 2,2'-bipyridyl complex, NAD+, malate dehydrogenase (NAD+-dependent oxaloacetate-decarboxylating) and fumarase was developed.

Visible-light driven 3-hydroxybutyrate synthesis from CO2 and acetone with the hybrid system of photocatalytic NADH regeneration and multi-biocatalysts.

Poly-3-hydroxybutyrate (PHB)-derived plastics are polymer materials with excellent biodegradability, being insoluble in water and relatively resistant to hydrolysis. There is a need for a method capable of synthesizing 3-hydroxybutyrate, a monomer of PHB, from a renewable material. In this work, visible-light driven 3-hydroxybutyrate from CO2 and acetone with the system consisting of triethanolamine, water-soluble zinc porphyrin, pentamethylcyclopentadienyl coordinated rhodium complex, NAD+ and a cell extract containing acetone carboxylase and 3-hydroxybutyrate dehydrogenase from Rhodobacter capsulatus SB1003 cultured in acetone-bicarbonate medium is established. In particular, the conversion yield for acetone to 3-hydroxybutyrate was improved up to 81% in this system after 7 h irradiation.

Theoretical study on CO2 reduction catalyzed by formate dehydrogenase using the cation radical of a bipyridinium salt with an ionic substituent as a co-enzyme.

Formate dehydrogenase from Candida boidinii (CbFDH; EC.1.2.1.2) is a useful enzyme for CO2 reduction to formate in the photoredox system of a visible-light sensitizer and an electron mediator in the presence of an electron donor. The electron mediator, cation radicals of 4,4'-bipyridinium salts (4,4'-BPs) act as the co-enzyme for CbFDH in the CO2 reduction to formate. We found that the CbFDH-catalyzed CO2 reduction to formate could be controlled by the ionic substituents introduced into the cation radical of 4,4'-BPs [Y. Amao, Sustainable Energy Fuels, 2018, 2, 1928-1950]. By using 1,1'-diaminoethyl-4,4'-bipyridinium salt (DABP), 1-aminoethyl-1'-methyl-4,4'-bipyridinium salt (AMBP), 1,1'-carboxymethyl-4,4'-bipyridinium salt (DCBP), and 1-carboxymethyl-1'-methyl-4,4'-bipyridinium salt (CMBP), the introduction of an amino-group into 4,4'-BP accelerates the CbFDH-catalyzed CO2 reduction to formate, while the introduction of a carboxy-group into 4,4'-BP slows the CO2 reduction to formate. This work clarified the direct interaction of the cation radicals of DABP, DCBP, AMBP, CMBP, and MV in the substrate-binding site of CbFDH by the docking simulation. In addition, a mechanistic investigation for the CbFDH-catalyzed CO2 reduction to formate with cation radicals of DABP, DCBP, AMBP, CMBP, and MV was carried out based on the energy of molecular orbitals calculated by density functional theory (DFT).

How does methylviologen cation radical supply two electrons to the formate dehydrogenase in the catalytic reduction process of CO2 to formate?

Formate dehydrogenase from Candida boidinii (EC.1.2.1.2; CbFDH) is a commercially available enzyme and can be easily handled as a catalyst for the CO2 reduction to formate in the presence of NADH, single-electron reduced methylviologen (MV+˙) and so on. It was found that the formate oxidation to CO2 with CbFDH was suppressed using the oxidized MV as a co-enzyme and the single-electron reduced MV (MV+˙) was effective for the catalytic activity of CbFDH for the CO2 reduction to formate compared with that using the natural co-enzyme of NADH [Y. Amao, Chem. Lett., 2017, 46, 780-788]. The CO2 reduction to formate catalyzed by CbFDH requires two molecules of the MV+˙. In order to clarify the two-electron reduction process using MV+˙ in the CO2 reduction to formate catalyzed with CbFDH, we attempted enzyme reaction kinetics, electrochemical and quantum chemical analyses. Kinetic parameters obtained from the enzymatic kinetic analysis metric revealed an index of affinity of MV+˙ for CbFDH in the CO2 reduction to formate. From the results of the electrochemical analysis, it was predicted that only one molecule of MV+˙ was bound to CbFDH, and the MV bound to CbFDH was to be necessarily re-reduced by the electron source outside of CbFDH to supply the second electron in the CO2 reduction to formate. From the results of docking simulation and density functional theory (DFT) calculations, it was indicated that one molecule of MV bound to the position close to CO2 in the inner part of the substrate binding pocket of CbFDH contributed to the two-electron CO2 reduction to formate.

Visible-light-driven CO2 reduction to formate with a system of water-soluble zinc porphyrin and formate dehydrogenase in ionic liquid/aqueous media.

Visible-light-driven CO2 reduction to formate with a system consisting of water-soluble zinc tetraphenylporphyrin tetrasulfonate (ZnTPPS), formate dehydrogenase from Candida boidinii (CbFDH) and methylviologen (MV) in the presence of triethanolamine (TEOA) as an electron donor in an ionic liquid, 1-ethyl-3-methylimidazolium dimethyl phosphate ([EMlm][Me2PO4])/aqueous media was investigated. The catalytic activity of CbFDH for formate oxidation to CO2 and CO2 reduction to formate did not decrease significantly even in [EMlm][Me2PO4]/aqueous media, compared with that in aqueous media. The visible-light-driven MV reduction by the photosensitization of ZnTPPS in [EMlm][Me2PO4]/aqueous media proceeds more efficiently than in the aqueous media system. In the visible-light-driven CO2 reduction to formate system of ZnTPPS, MV and CbFDH with [EMlm][Me2PO4]/aqueous media, moreover, the formate production concentration after 180 min decreased by only 20% as compared with the system in aqueous media.

Visible-light driven hydrogen production using chlorophyll derivatives conjugated with a viologen moiety in the presence of platinum nanoparticles.

The utilization of the light-harvesting and electron-transferring function of chlorophylls (Chls) has received attention for visible-light driven hydrogen production. In this work, a series of Chl derivatives based on pyropheophorbide-a (Pyro-a) conjugated with a viologen moiety, including a Pyro-a methyl ester directly bonded with the viologen at the 3-position 1, its 31-methylene analog 2 and Pyro-a connected with the viologen in the 17-substituent 3, were synthesized from chemical modification of naturally occurring Chl-a and characterized in terms of their photochemical and photophysical properties. As the photoexcited singlet state of the Pyro-a moiety was strongly quenched by the viologen moiety in a molecule, the effective photoinduced intramolecular electron transfer from Pyro-a to the bonded viologen moiety occurred. Moreover, these molecules were applied as a photosensitizer in the system for visible-light driven hydrogen production with platinum nanoparticles via intramolecular reduction of the bonded viologen moiety. Efficient photoreduction of external methyl viologen and successive hydrogen production on platinum nanoparticles were achieved using the synthetic conjugate of Pyro-a with the viologen moiety as a photosensitizer. In particular, effective visible-light driven hydrogen production was accomplished using 3 and platinum nanoparticles via the reduction of external methyl viologen.

Development of a dye molecule-biocatalyst hybrid system with visible-light induced carbon-carbon bond formation from CO2 as a feedstock.

Recently, CO2 utilization technology, including artificial photosynthesis, has received much attention. In this field, CO2 is used as a feedstock for fuels, polymers and in other chemical processes. Of note are malic enzymes (MEs) which catalyze the reaction of malic acid to pyruvic acid and CO2 with the co-enzyme NADP+, and catalyze the reverse reaction of pyruvic acid and CO2 to malic acid with the co-enzyme NADPH. Thus, MEs are also an attractive biocatalyst for carbon-carbon bond formation from CO2. Studies of the visible light-induced malic acid production from pyruvic acid and CO2 using an electron donor, a photosensitizer, an electron mediator, ferredoxin-NADP+ reductase, NADP+, and ME have been reported. However, modification of these systems is required, as they are very complicated. In this study, the visible light-induced carbon-carbon bond formation from pyruvic acid and CO2 with ME using the photoreduction of 1,1'-diphenyl-4,4'-bipyridinium salt derivatives as a novel electron mediator with water-soluble tetraphenylporphyrin tetrasulfonate (H2TPPS) in the presence of triethanolamine (TEOA) as an electron donor was developed. When a sample solution containing TEOA, H2TPPS, 1,1'-diphenyl-4,4'-bipyridinium salt derivative, pyruvic acid, and ME in CO2-saturated bis-tris buffer was irradiated, the major product was oxaloacetic acid. Thus, a visible light-induced photoredox system for carbon-carbon bond formation from CO2 with ME using 1,1'-diphenyl-4,4'-bipyridinium salt derivative as an electron mediator was developed.

CO2 Photoreduction by Formate Dehydrogenase and a Ru-Complex in a Nanoporous Glass Reactor.

In this study, we demonstrated the conversion of CO2 to formic acid under ambient conditions in a photoreduction nanoporous reactor using a photosensitizer, methyl viologen (MV2+), and formate dehydrogenase (FDH). The overall efficiency of this reactor was 14 times higher than that of the equivalent solution. The accumulation rate of formic acid in the nanopores of 50 nm is 83 times faster than that in the equivalent solution. Thus, this CO2 photoreduction nanoporous glass reactor will be useful as an artificial photosynthesis system that converts CO2 to fuel.

Artificial leaf device for solar fuel production.

Solar fuels, such as hydrogen gas produced from water and methanol produced from carbon dioxide reduction by artificial photosynthesis, have received considerable attention. In natural leaves the photosynthetic proteins are well-organized in the thylakoid membrane. To develop an artificial leaf device for solar low-carbon fuel production from CO2, a chlorophyll derivative chlorin-e6 (Chl-e6; photosensitizer), 1-carboxylundecanoyl-1'-methyl-4,4'-bipyrizinium bromide, iodide (CH3V(CH2)9COOH; the electron carrier) and formate dehydrogenase (FDH) (the catalyst) immobilised onto a silica-gel-based thin layer chromatography plate (the Chl-V-FDH device) was investigated. From luminescence spectroscopy measurements, the photoexcited triplet state of Chl-e6 was quenched by the CH3V(CH2)9COOH moiety on the device, indicating the photoinduced electron transfer from the photoexcited triplet state of Chl-e6 to the CH3V(CH2)9COOH moiety. When the CO2-saturated sample solution containing NADPH (the electron donor) was flowed onto the Chl-V-FDH device under visible light irradiation, the formic acid concentration increased with increasing irradiation time.

Immobilization and Photocurrent Activity of a Light-Harvesting Antenna Complex II, LHCII, Isolated from a Plant on Electrodes.

A light-harvesting (LH) antenna complex II, LHCII, isolated from spinach was immobilized onto an indium tin oxide (ITO) electrode with dot patterning of 3-aminopropyltriethoxysilane (APS) by utilizing electrostatic interactions between the cationic surface of the electrode and the anionic surface of stromal side of the LHCII polypeptide. Interestingly, the illumination of LHCII assembled onto the ITO electrode produced a photocurrent response that depends on the wavelength of the excitation light. Further, LHCII was immobilized onto a TiO2 nanostructured film to extend for the development of a dye-sensitized biosolar cell system. The photocurrent measured in the iodide/tri-iodide redox system of an ionic liquid based electrolyte on the TiO2 system showed remarkable enhancement of the conversion efficiency, as compared to that on the ITO electrode.

Photoinduced biohydrogen production from biomass.

Photoinduced biohydrogen production systems, coupling saccharaides biomass such as sucrose, maltose, cellobiose, cellulose, or saccharides mixture hydrolysis by enzymes and glucose dehydrogenase (GDH), and hydrogen production with platinum colloid as a catalyst using the visible light-induced photosensitization of Mg chlorophyll-a (Mg Chl-a) from higher green plant or artificial chlorophyll analog, zinc porphyrin, are introduced.

Optical oxygen-sensing properties of porphyrin derivatives anchored on ordered porous aluminium oxide plates.

An optical oxygen-sensing activity of anchored porphyrin derivatives on ordered porous aluminium oxide plates was studied in relevance to development of new oxygen-sensing systems. Porphyrin derivatives, 5,10,15,20-tetrakis(4-carboxylundecane-1-oxy)porphyrin, 5-[4-(11-carboxylundecane-1-oxy)-10,15,20-triphenyl]porphyrin, 5-(4-carboxylphenyl)-10,15,20-triphenylporphyrin, and their platinum complexes, 5,10,15,20-tetrakis(4-carboxylundecane-1-oxy)porphyrinatoplatinum(II), 5-[4-(11-carboxylundecane-1-oxy)-10,15,20-triphenyl]porphyrinatoplatinum(II), 5-(4-carboxylphenyl)-10,15,20-triphenylporphyrinatoplatinum(II), were synthesized and anchored by an equilibrium adsorption method on aluminium oxide plates, which were prepared by an anodic oxidation. The excitation spectra of the porphyrin-anchored layers showed a broadened and blue-shifted Soret band compared with the corresponding porphyrins in DMSO. The luminescence intensity decreased with increasing oxygen concentrations. The oxygen-sensing ability estimated from I(0)/I(100) (I(0) and I(100) denote the luminescence intensity in 0 and 100% oxygen) was 9.08, 6.78, 8.71, 81.9, 35.5, and 39.1, which are greater than those of corresponding porphyrin derivatives in DMSO under the measured conditions, and indicates the remarkable enhancement effect of platinum(II). Non-linear Stern-Volmer plots were well fitted by the two component system to give the oxygen-sensitive constant (K(SV1)/%(-1)), the oxygen-insensitive constant (K(SV2)/%(-1)), and the former contribution (f(1)): 0.232, 3.32 x 10(-2), and 0.642; 0.141, 2.05 x 10(-2), and 0.687; 0.143, 1.05 x 10(-2), and 0.882; 17.3, 7.04 x 10(-3), and 0.980; 10.2, 1.43 x 10(-2), and 0.935; 16.3, 8.35 x 10(-3), and 0.954. The response time for the change of the atmospheric gas from argon to oxygen was 9.4 s, 12.5 s, 9.6 s, 5.0 s, 8.9 s, and 4.6 s, indicating the shortening effect of platinum. The reverse effect of platinum was observed in the change from oxygen to argon: 15.5 s, 17.0 s, 20.8 s, 667.4 s, 590.1 s, and 580.4 s, indicating the specific interaction of oxygen to the platinum(II) center.

Photovoltaic conversion using Zn chlorophyll derivative assembled in hydrophobic domain onto nanocrystalline TiO2 electrode.

Photovoltaic conversion using zinc chlorin-e6 (ZnChl-e6), which is zinc chlorophyll-a derivative, and fatty acid (myristic acid or cholic acid) co-adsorbed nanocrystalline TiO2 layer onto ITO glass (OTE) electrode is developed. The maximum peaks of photocurrent action spectrum of the ZnChl-e6 adsorbed TiO2 layer onto OTE (ZnChl-e6/TiO2) are 400, 660 and 800 nm, respectively. Especially the IPCE value at 800 nm (7.5%) is larger than that of 660 nm (6.9%). This result indicates that ZnChl-e6 molecules is aggregated or formed dimer on a nanocrystalline TiO2 layer onto OTE and the absorption band is shifted to near IR region. The photocurrent action spectrum of ZnChl-e6 and cholic acid adsorbed TiO2 layer onto OTE (ZnChl-e6-Cho/TiO2 is similar to that of the UV-vis absorption spectrum in methanol solution, and IPCE values at 400 and 660 nm (8.1%) increase and the IPCE value at 800 nm (4.1%) decreases, indicating that the aggregation of ZnChl-e6 molecules on the TiO2 is suppressed by cholic acid. By using ZnChl-e6-Cho/TiO2, the short-circuit photocurrent density and open-circuit photovoltage also increase compared with that of ZnChl-e6 adsorbed nanocrystalline TiO2 electrode.

Photochemical and photophysical properties of carotenoid immobilized on a surfactant micellar medium including chlorophyll as an artificial photosynthesis system.

To develop an artificial photosynthesis model, the anionic water-soluble carotenoid dye crocetin was electrostatically immobilized onto the surface of cationic surfactant cetyltrimethylammonium bromide (CTAB) micellar medium including Mg chlorophyll-a and b (MgChl-a and b) (Cro/MgChl), and its photophysical properties were studied using UV-vis absorption and fluorescence spectroscopy. The fluorescence of MgChl-a and b was observed, with the excitation wavelength attributed to the absorption band of crocetin, indicating that photo-induced energy transfer from the photoexcited state of crocetin to MgChl-a and b occurs. The photostability of MgChl-a and b in Cro/MgChl was investigated under continuous irradiation. After 60 min irradiation, the absorbance decreases at 660 nm Cro/MgChl and MgChl-a/b, without crocetin, were 3.0 and 17%, respectively. These results indicate that the photo-bleaching rate of MgChl-a/b in Cro/MgChl on irradiation is suppressed by the crocetin molecule on the surface of micelles.

Light-harvesting properties of zinc complex of chlorophyll-a from spirulina in surfactant micellar media.

Zn chlorophyll-a was prepared from Mg chlorophyll-a from spirulina and the optical properties of the ground state and the photoexited state of Zn chlorophyll-a in aqueous surfactant micellar media were studied using UV-vis absorption, fluorescence emission spectra, electrochemical and fluorescence lifetime measurements. In comparison of the UV-vis absorption and fluorescence emission spectra of Zn chlorophyll-a and Mg chlorophyll-a, the blue-shift in the absorption bands and emission peak of Zn chlorophyll-a was observed. The energies of the first excited singlet state of Zn chlorophyll-a was 1.87 eV. The first oxidation and reduction potentials of the photoexcited singlet state of Zn chlorophyll-a were -0.67 and 0.60 V, respectively. Fluorescence lifetime of Zn chlorophyll-a was 9.0 ns in CTAB micellar solution. The fluorescence lifetime of Zn chlorophyll-a is shorter than that of Mg chlorophyll-a (9.8 ns). The photositability of Zn chlorophyll-a was superior to that of Mg chlorophyll-a in various pH conditions.

Photoreduction behavior of cytochrome c by zinc porphyrin in lipid media.

To elucidate the role of cardiolipin (CL) on redox behavior of cytochrome c (cyt c (III)), the photoreduction of cyt c using the photosensitization of zinc tetraphenylporphyrin in presence of triethanolamine (TEOA) as a sacrificial electron-donating reagent in various lipid media were studied. The initial rate of cyt c (III) photoreduction in various lipid, CL, l-alpha-phosphatidic acid (PA), dimethyldipalmitoylammonium bromide (DMPA) and Triton X-100 media were 1.0, 0.73, 0.80 and 0.67 micromol dm-3 min-1, respectively. The cyt c (III) photoreduction rate slightly increased by the addition of CL.

Near-IR light-sensitized voltaic conversion system using nanocrystalline TiO2 film by Zn chlorophyll derivative aggregate.

A Zn chlorophyll-a derivative, Zn chlorin-e6 (ZnChl-e6), adsorbed onto a nanocrystalline TiO2 film (ZnChl-e6/TiO2) electrode was prepared, and the photovoltaic properties of the ZnChl-e6/TiO2 electrode were studied. The absorption peaks of ZnChl-e6/TiO2 observed at 420, 654, and 795 nm were attributed to the ZnChl-e6 molecules aggregating onto TiO2 film. The fluorescence attributed to the ZnChl-e6 monomer and aggregate was observed at 710 and 820 nm, respectively, and the fluorescence in both cases was quenched by TiO2 particles. The maximum of the incident photon-to-current conversion efficiency (IPCE) value in the photocurrent action spectrum was 800 nm, and the IPCE value was 7.0%. ZnChl-e6 molecules formed aggregates on a nanocrystalline TiO2 film electrode. From the photocurrent-photovoltage characteristics of the ZnChl-e6/TiO2 electrode irradiated with 100 mW cm(-2), the short-circuit photocurrent (I(SC)) was found to be 0.19 mA cm(-2) and the open-circuit photovoltage (V(OC)) was found to be 375 mV. The maximum power was estimated to be 28.7 microW cm(-2), and the fill factor (FF) was estimated to be 40.1%. A near-IR light induced photovoltaic conversion system using a ZnChl-e6 aggregate formed onto a nanocrystalline TiO2 film electrode was achieved.

Optical CO(2) sensor of the combination of colorimetric change of alpha-naphtholphthalein in poly(isobutyl methacrylate) and fluorescent porphyrin in polystyrene.

An optical CO(2) sensor based on the overlay of the CO(2) induced absorbance change of pH indicator dye alpha-naphtholphthalein in poly(isobutyl methacrylate) (polyIBM) layer with the fluorescence of tetraphenylporphyrin (TPP) in polystyrene layer is developed. The observed luminescence intensity from TPP at 655nm increased with increasing the CO(2) concentration. The ratio I(100)/I(0) value of the sensing film consisting of alpha-naphtholphthalein in polyIBM and TPP in polystyrene layer, where I(0) and I(100) represent the detected luminescence intensities from a layer exposed to argon and CO(2) saturated conditions, respectively, that the sensitivity of the sensor, is estimated to be 192. The response and recovery times of the sensing film are less than 6.0s for switching from argon to CO(2), and for switching from CO(2) to argon. The signal changes are fully reversible and no hysterisis is observed during the measurements. The highly sensitive optical CO(2) sensor based on fluorescence intensity changes of TPP due to the absorption change of alpha-naphtholphthalein in polyIBM layer with CO(2) is achieved.

Lactic acid production with lactate dehydrogenase using the visible light sensitization of zinc porphyrin.

Lactic acid production with L-lactate dehydrogenase from Pig heart (LDH) and reduced methyl viologen produced by the visible light photosensitization of zinc tetrakis(4-methylpyridyl)porphyrin (ZnTMPyP) was investigated. When the sample solution containing triethanolamine as an electron-donating reagent, ZnTMPyP, methyl viologen as an electron carrier, pyruvic acid and LDH in potassium phosphate buffer (pH 7) was irradiated, lactic acid production was observed. After 240 min irradiation, the amount of lactic acid production and the yield of pyruvic acid to lactic acid were estimated to be 0.17 mmol dm(-3) and 17.0%, respectively.