Stability and electronic properties of praseodymium-doped silicon clusters PrSin (<Emphasis Type="Italic">n</Emphasis> = 12–21)

The neutral PrSi _n (n = 12–21) species considering various spin configurations were systematically studied using PBE0 and B3LYP schemes in combination with relativistic small-core potentials (ECP28MWB) for Pr atoms and cc-pVTZ basis set for Si atoms. The total energy, growth-pattern, equilibrium geometry, relative stability, hardness, charge transfer, and magnetic moments are calculated and discussed. The results reveal that when n < 20, the ground-state structure of PrSi _n evaluated to be prolate clusters. Starting from n = 20, the ground-state structures of PrSi _n are evaluated to be endohedral cagelike clusters. Although the relative stabilities based on various binding energies and different functional is different from each other, the consensus is that the PrSi₁₃, PrSi₁₆, PrSi₁₈, and PrSi₂₀ are more stable than the others, especially the PrSi₂₀. Analyses of hardness show that introducing Pr into Si _n (n = 12–21) elevates the photochemical sensitivity, especially for PrSi₂₀. Calculated result of magnetic moment and charge transfer shows that the 4f electrons of Pr in the clusters are changed, especially in endohedral structures such as PrSi₂₀, in which one electron transfers from 4f to 5d orbital. That is, the 4f electron of Pr in the clusters participates in bonding. The way to participate in bonding is that a 4f electron transfers to 5d orbital. Although the 4f electron of Pr atom participates in bonding, the total magnetic moment of PrSi _n is equal to that of isolated Pr atom. The charge always transfers from Pr atom to Si _n cluster for the ground state structures of PrSi_n (n = 12–19), but charge transfer is reverse for n ≥ 20. The largest charge transfer for endohedral structure reveals that the bonding between Pr and Si _n is ionic in nature and very strong. The fullerenelike structure of PrSi₂₀ is the most stable among all of these clusters and can act as the building blocks for novel functional nanotubes.     

Interaction of various types of photosystem I complexes with exogenous electron acceptors

Interaction of photosystem I (PS I) complexes from cyanobacteria Synechocystis sp. PCC 6803 containing various quinones in the A₁-site (phylloquinone PhQ in the wild-type strain (WT), and plastoquinone PQ or 2,3-dichloronaphthoquinone Cl ₂ NQ in the menB deletion strain) and different numbers of Fe₄S₄ clusters (intact WT and F_X-core complexes depleted of F_A/F_B centers) with external acceptors has been studied. The efficiency of interaction was estimated by measuring the light-induced absorption changes at 820 nm due to the reduction of the special pair of chlorophylls (P₇₀₀ ⁺) by an external acceptor(s). It was shown that externally added Cl ₂ NQ is able to effectively accept electrons from the terminal iron-sulfur clusters of PS I. Moreover, the efficiency of Cl ₂ NQ as external acceptor was higher than the efficiency of the commonly used artificial electron acceptor, methylviologen (MV) for both the intact WT PS I and for the F_X-core complexes. The comparison of the efficiency of MV interaction with different types of PS I complexes revealed gradual decrease in the following order: intact WT?>?menB?>?F_X-core. The effect of MV on the recombination kinetics in menB complexes of PS I with Cl ₂ NQ in the A₁-site differed significantly from all other PS I samples. The obtained effects are considered in terms of kinetic efficiency of electron acceptors in relation to thermodynamic and structural characteristics of PS I complexes.     

Theoretical characterization on photoelectric properties of benzothiadiazole- and fluorene-based small molecule acceptor materials for the organic photovoltaics

The upper efficiency of heterojunction organic photovoltaics depends on the increased open-circuit voltage (V _oc) and short-circuit current (J _sc). So, a higher lowest unoccupied molecular orbital (LUMO) level is necessary for organic acceptor material to possess higher V _oc and more photons absorbsorption in the solar spectrum is needed for larger J _sc. In this article, we theoretically designed some small molecule acceptors (2～5) based on fluorene (F), benzothiadiazole, and cyano group (CN) referring to the reported acceptor material 2-[{7-(9,9-di-n-propyl-9H-fluoren-2-yl)benzo[c][1,2,5]thiadiazol-4-yl}methylene]malononitrile (1), the crucial parameters affecting photoelectrical properties of compounds 2～5 were evaluated by the density functional theory (DFT) and time dependent density functional theory (TDDFT) methods. The results reveal that compared with 1, 3 and 4 could have the better complementary absorption spectra with P3HT, the increased LUMO level, the improved V _oc, and the decreased electronic organization energy (λ _e). From the simulation of transition density matrix, it is very clear that the excitons of molecules 3 and 4 are easier to separate in the material surface. Therefore, 3 and 4 may become potential acceptor candidates for organic photovoltaic cells. In addition, with the increased number of CN, the optoelectronic properties of the molecules show a regular change, mainly improve the LUMO level, energy gap, V _oc, and absorption intensity. In summary, reasonably adjusting CN can effectively improve the photovoltaic properties of small molecule acceptors.

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Graphical Abstract Structure–property relationship of small molecule acceptors could be rationally evaluated in the article. The changes of conjugate length and CN are important strategies to alter the photovoltaic properties of small molecule acceptors. Therefore, taking the K12/1 as a reference, we have theoretically designed a series of small molecule acceptors (2–4). The calculated results by means of DFT and TDDFT manifest that molecules 3 and 4 have the better complementary absorption spectra with P3HT, the increased LUMO level, the improved V _oc, the decreased electronic organization energy and the easier separation in the material surface than 1. In summary, reasonably increasing conjugate length and decreasing CN can effectively improve the PCE, which will provide a theoretical guideline for the design and synthesis of new small molecule acceptors.

     

Kinetic modeling of electron transfer reactions in photosystem I complexes of various structures with substituted quinone acceptors

The reduction kinetics of the photo-oxidized primary electron donor P₇₀₀ in photosystem I (PS I) complexes from cyanobacteria Synechocystis sp. PCC 6803 were analyzed within the kinetic model, which considers electron transfer (ET) reactions between P₇₀₀, secondary quinone acceptor A₁, iron-sulfur clusters and external electron donor and acceptors – methylviologen (MV), 2,3-dichloro-naphthoquinone (Cl₂NQ) and oxygen. PS I complexes containing various quinones in the A₁-binding site (phylloquinone PhQ, plastoquinone-9 PQ and Cl₂NQ) as well as F _X-core complexes, depleted of terminal iron–sulfur F _A/F _B clusters, were studied. The acceleration of charge recombination in F _X-core complexes by PhQ/PQ substitution indicates that backward ET from the iron–sulfur clusters involves quinone in the A₁-binding site. The kinetic parameters of ET reactions were obtained by global fitting of the P₇₀₀ ⁺ reduction with the kinetic model. The free energy gap ΔG ₀ between F _X and F _A/F _B clusters was estimated as ?130 meV. The driving force of ET from A₁ to F _X was determined as ?50 and ?220 meV for PhQ in the A and B cofactor branches, respectively. For PQ in A_1A-site, this reaction was found to be endergonic (ΔG ₀?=?+75 meV). The interaction of PS I with external acceptors was quantitatively described in terms of Michaelis–Menten kinetics. The second-order rate constants of ET from F _A/F _B, F _X and Cl₂NQ in the A₁-site of PS I to external acceptors were estimated. The side production of superoxide radical in the A₁-site by oxygen reduction via the Mehler reaction might comprise ≥0.3% of the total electron flow in PS I.     

Heterologous expression and characterisation of a laccase from <Emphasis Type="Italic">Colletotrichum lagenarium</Emphasis> and decolourisation of different synthetic dyes

Laccases have received considerable attention in recent decades because of their ability to oxidise a large spectrum of phenolic and non-phenolic organic substrates and highly recalcitrant environmental pollutants. In this research, a laccase gene from Colletotrichum lagenarium was chemically synthesised using yeast bias codons and expressed in Pichia pastoris. The molecular mass of the recombinant laccase was estimated to be 64.6 kDa by SDS–PAGE, and the enzyme exhibited maximum activity at pH 3.6–4.0 but more stability in buffer with higher pH (>pH 3.6). The optimal reaction temperature of the enzyme was 40 °C, beyond which stability significantly decreased. By using 2,2′-azino-bis-(3-ethylbenzothiazoline)-6-sulphonate (ABTS) as a substrate, K _m and V _max values of 0.34 mM and 7.11 mM min^?1 mg^?1, respectively, were obtained. Using ABTS as a mediator, the laccase could oxidise hydroquinone to p-benzoquinone and decolourise the synthetic dyes malachite green, crystal violet and orange G. These results indicated that the laccase could be used to treat industrial effluents containing artificial dyes.     

Impacts on Micro- and Macro-Structure of Thermally Stabilised Whey Protein-Pectin Complexes: A Fluorescence Approach

Stability of whey protein-pectin complexes is an essential criterion for their application in different food matrices. The impact of process parameters on micro- and macro-structural characteristics of thermally stabilised whey protein-pectin complexes was investigated using fluorescence spectroscopy, ζ-potential measurements, dynamic light scattering and phase separation. Complexes prepared from whey protein isolate (WPI) and pectins with different degrees of esterification (HMP, LMP) were generated at different biopolymer concentrations (WPI + pectin: 5.0 % + 1.0 %, c _{h i g h} ; 2.75 % + 0.55 %, c _{m e d} ; 0.5 % + 0.1 %, c _{l o w} ), heating temperatures (80-90^°C) and pH levels (6.1-4.0). Micro- and macro-structural characteristics of the complexes depended on concentration level and degree of esterification, with complexes being more sensitive towards environmental changes at c _{l o w} than at c _{m e d} and c _{h i g h} . WPI-LMP complexes exhibited sizes <1 μm suitable for micro-encapsulation, whereas WPI-HMP complexes at c _{m e d} achieved sizes from 1-10 μm and at c _{h i g h} from 10-200 μm underlining their potential as fat-replacers and structuring agents, respectively. Slopes and intercepts derived from intensity ratios of fluorescence spectra gave insights into the state of unfolding of β-lactoglobulin within the complexes and thus about the protective effect of pectin addition.     

Enantioconvergent hydrolysis of racemic styrene oxide at high concentration by a pair of novel epoxide hydrolases into (<Emphasis Type="Italic">R</Emphasis>)-phenyl-1,2-ethanediol

Objectives

To prepare (R)-phenyl-1,2-ethanediol ((R)-PED) with high enantiomeric excess (ee _p) and yield from racemic styrene oxide (rac-SO) at high concentration by bi-enzymatic catalysis.

Results

The bi-enzymatic catalysis was designed for enantioconvergent hydrolysis of rac-SO by a pair of novel epoxide hydrolases (EHs), a Vigna radiata EH3 (VrEH3) and a variant (AuEH2^A250I) of Aspergillus usamii EH2. The simultaneous addition mode of VrEH3 and AuEH2^A250I, exhibiting the highest average turnover frequency (aTOF) of 0.12 g h^?1 g^?1, was selected, by which rac-SO (10 mM) was converted into (R)-PED with 92.6% ee _p and 96.3% yield. Under the optimized reaction conditions: dry weight ratio 14:1 of VrEH3-expressing E. coli/vreh3 to AuEH2^A250I-expressing E. coli/Aueh2 ^A250I and reaction at 20 °C, rac-SO (10 mM) was completely hydrolyzed in 2.3 h, affording (R)-PED with 98% ee _p. At the weight ratio 0.8:1 of rac-SO to two mixed dry cells, (R)-PED with 97.4% ee _p and 98.7% yield was produced from 200 mM (24 mg/ml) rac-SO in 10.5 h.

Conclusions

Enantioconvergent hydrolysis of rac-SO at high concentration catalyzed by both VrEH3 and AuEH2^A250I is an effective method for preparing (R)-PED with high ee _p and yield.

     

Choice of a spin singlet or triplet: electronic properties of Bis-Co(II), Bis-Ni(II), Bis-Cu(II) and Bis-Zn(II) oxygen doubly N-confused hexaphyrin (1.1.1.1.1.1)

Fused hexaphyrins have many physical and chemical properties and can coordinate transition metal ions. In this study, we investigated the geometric structure, charge decomposition analysis (CDA), spin density, frontier molecular orbital (FMO) compositions and absorption spectra of four oxygen doubly N-confused hexaphyrin (1.1.1.1.1.1) (ONCP) complexes with the metal ions Co(II), Ni(II), Cu(II) and Zn(II) (designated ONCP-d-Co, ONCP-d-Ni, ONCP-d-Cu and ONCP-d-Zn). Based on their energies, geometric structures, FMO characteristics and comparison to experiments, ONCP-d-Co and ONCP-d-Cu have the mix-states of the triplet state and broken-symmetry state (antiferromagnetic state) rather than the spin singlet of a closed shell as previously reported. Moreover, based on analyses of the spin density and spin population of the spin triplet ONCP-d-Co and ONCP-d-Cu complexes, the charge transfer in ONCP-d-Cu is greater than that in ONCP-d-Co because the spin density in ONCP-d-Cu is concentrated not only on the Cu ion but also on the ONCP ligand. Thus, the CDA value for ONCP-d-Cu is larger. Finally, through comparative analysis of the FMO compositions and absorption spectra, the complexes and ligand are shown to have very similar absorption spectra with characteristics that arise mainly from π?→?π* transitions both in the B-band and the Q-band, which is due to the FMO compositions being dominated by the highly delocalized conjugated system, rather than by the metal ions. The absorption maxima of the Q-band are ONCP-d-Co (1020 nm)?>?ONCP-d-Zn (1012 nm)?>?ONCP-d-Ni (997 nm)?>?ONCP-d-Cu (988 nm), which is inversely proportional to the energy gap in their FMOs.

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Graphical Abstract The present work investigates the geometric structure, charge decomposition analysis (CDA), spin density, frontier molecular orbital (FMO) compositions and absorption spectra of four oxygen doubly N-confused hexaphyrin (1.1.1.1.1.1) (ONCP) complexes with the metal ions Co(II), Ni(II), Cu(II) and Zn(II) (designated ONCP-d-Co, ONCP-d-Ni, ONCP-d-Cu and ONCP-d-Zn). Based on their energies, geometric structures, FMO characteristics and comparison to experiments, ONCP-d-Co and ONCP-d-Cu have the mix-state of the triplet state and broken-symmetry state (antiferromagnetic state) rather than the spin singlet of a close shell as were previously reported. Meanwhile, ONCP-d-Ni and ONCP-d-Zn show spin singlet structure. The calculated CDA shows the following order: ONCP-d-Cu (1.487)?>?ONCP-d-Ni (1.255)?>?ONCP-d-Co (1.211)?>?ONCP-d-Zn (1.201). Through comparisons of spin density and spin populations of ONCP-d-Co and ONCP-d-Cu, charge transfer between Cu and ligand ONCP is greater than that of Co and ONCP, which makes the CDA value of ONCP-d-Cu obviously larger than that of the other complexes

     

Acetaldehyde kinetics of enological yeast during alcoholic fermentation in grape must

Acetaldehyde strongly binds to the wine preservative SO₂ and, on average, causes 50–70 mg l^?1 of bound SO₂ in red and white wines, respectively. Therefore, a reduction of bound and total SO₂ concentrations necessitates knowledge of the factors that affect final acetaldehyde concentrations in wines. This study provides a comprehensive analysis of the acetaldehyde production and degradation kinetics of 26 yeast strains of oenological relevance during alcoholic fermentation in must under controlled anaerobic conditions. Saccharomyces cerevisiae and non-Saccharomyces strains displayed similar metabolic kinetics where acetaldehyde reached an initial peak value at the beginning of fermentations followed by partial reutilization. Quantitatively, the range of values obtained for non-Saccharomyces strains greatly exceeded the variability among the S. cerevisiae strains tested. Non-Saccharomyces strains of the species C. vini, H. anomala, H. uvarum, and M. pulcherrima led to low acetaldehyde residues (<10 mg l^?1), while C. stellata, Z. bailii, and, especially, a S. pombe strain led to large residues (24–48 mg l^?1). Acetaldehyde residues in S. cerevisiae cultures were intermediate and less dispersed (14–34 mg l^?1). Addition of SO₂ to Chardonnay must triggered significant increases in acetaldehyde formation and residual acetaldehyde. On average, 0.33 mg of residual acetaldehyde remained per mg of SO₂ added to must, corresponding to an increase of 0.47 mg of bound SO₂ per mg of SO₂ added. This research demonstrates that certain non-Saccharomyces strains display acetaldehyde kinetics that would be suitable to reduce residual acetaldehyde, and hence, bound-SO₂ levels in grape wines. The acetaldehyde formation potential may be included as strain selection argument in view of reducing preservative SO₂ concentrations.     

First study on characterization of virulence and antibiotic resistance genes in verotoxigenic and enterotoxigenic <Emphasis Type="Italic">E</Emphasis>. <Emphasis Type="Italic">coli</Emphasis> isolated from raw milk and unpasteurized traditional cheeses in Romania

The study focused on the incidence of enterotoxigenic Escherichia coli (ETEC) and verotoxigenic E. coli (VTEC) in raw milk and traditional dairy cheeses marketed in Romania, characterizing the virulence and antibiotic resistance genes of these isolates. One hundred and twenty samples of raw milk and 80 samples of unpasteurized telemy cheese were collected and cultured according to the international standard protocol. All the characteristic E. coli cultures were analyzed for the presence of STa, STb, LT, stx1, and stx2 toxicity genes. The ETEC/VTEC strains were tested for the presence of antibiotic resistance genes, such as aadA1, tetA, tetB, tetC, tetG, dfrA1, qnrA, aaC, sul1, bla _SHV , bla _CMY , bla _TEM , and ere(A), using PCR. The results showed that 27 samples (18.62%) were positive for one of the virulence genes investigated. 48.1% (n = 13) tested positive at the genes encoding for tetracycline resistance, tetA being the most prevalent one (61.5%; n = 8). A high percent (33.3%; n = 9) revealed the beta-lactamase (bla _TEM ) resistance gene, and none of the samples tested positive for bla _CMY and bla _SHV genes. The genes responsible for resistance to sulfonamides (sul1) and trimethoprim (dfrA1) were detected in rates of 14.8% (n = 4) and 7.4% (n = 2), respectively. E. coli is highly prevalent in raw milk and unpasteurized cheeses marketed in Romania. These strains might represent an important reservoir of resistance genes which can easily spread into other European countries, given the unique market.     

Impact of elevated CO<Subscript>2</Subscript> in <Emphasis Type="Italic">Casuarina equisetifolia</Emphasis> rooted stem cuttings inoculated with <Emphasis Type="Italic">Frankia</Emphasis>

Impact of different levels of elevated CO ₂ on the activity of Frankia (Nitrogen-fixing actinomycete) in Casuarina equisetifolia rooted stem cuttings has been studied to understand the relationship between C. equisetifolia, Frankia and CO₂. The stem cuttings of C. equietifolia were collected and treated with 2000 ppm of Indole Butyric Acid (IBA) for rooting. Thus vegetative propagated rooted stem cuttings of C. equisetifolia were inoculated with Frankia and placed in the Open top chambers (OTC) with elevated CO₂ facilities. These planting stocks were maintained in the OTC for 12 months under different levels of elevated CO₂ (ambient control, 600 ppm, 900 ppm). After 12 months, the nodule numbers, bio mass, growth, and photosynthesis of C. equisetifolia rooted stem cuttings inoculated with Frankia were improved under 600 ppm of CO₂. The rooted stem cuttings of C. equisetifolia inoculated with Frankia showed a higher number of nodules under 900 ppm of CO₂ and cuttings without Frankia inoculation exhibited poor growth. Tissue Nitrogen (N) content was also higher under 900 ppm of CO₂ than ambient control and 600 ppm levels. The photosynthetic rate was higher (17.8 μ mol CO₂ m^?2 s^?1) in 900 ppm of CO₂ than in 600 ppm (13.2 μ mol CO₂ m^?2 s^?1) and ambient control (8.3 μ mol CO₂ m^?2 s^?1). This study showed that Frankia can improve growth, N fixation and photosynthesis of C. equietifolia rooted stem cuttings under extreme elevated CO₂ level conditions (900 ppm).     

Parasitism Rate of <Emphasis Type="Italic">Habrobracon hebetor</Emphasis> to <Emphasis Type="Italic">Ephestia kuehniella</Emphasis> Larvae: Residual Effect of Deltamethrin,Fenvalerate and Azadirachtin

Sublethal concentrations of chemical insecticides may cause changes in some behavioral characteristics of natural enemies such as functional responses. The residual effect of three synthetic insecticides including deltamethrin, fenvalerate and azadirachtin were studied on functional response of Habrobracon hebetor Say to Ephestia kuehniella Zeller larvae. Seven host densities (2, 4, 8, 16, 32, 64 and 96) were used during a 24 h period. The resulting data were appropriately fit to Type II functional response models in all treatments: (1) control (0.0916 h^?1; and T _h  = 0.2011 h); (2) deltamethrin (a = 0.0839 h^?1; and T _h  = 0.3560 h); (3) fenvalerate (a = 0.0808 h^?1 and T _h  = 0.3623 h); and (4) azadirachtin (a = 0.0900 h^?1 and T _h  = 0.2042 h). Maximum theoretical parasitism rate (T/T _h ) was 119.34 estimated for control wasps. There was no significant difference between the values of attack rates (a and a + D _a ) in all treatments while the handling time was statistically affected in female wasps treated with fenvalerate. Our findings will be useful in safe application of these insecticides in pest management programmes.     

A novel NADPH-dependent reductase of <Emphasis Type="Italic">Sulfobacillus acidophilus</Emphasis> TPY phenol hydroxylase: expression,characterization, and functional analysis

The reductase component (MhpP) of the Sulfobacillus acidophilus TPY multicomponent phenol hydroxylase exhibits only 40 % similarity to Pseudomonas sp. strain CF600 phenol hydroxylase reductase. Amino acid sequence alignment analysis revealed that four cysteine residues (Cys-X ₄ -Cys-X ₂ -Cys-X _29-35 -Cys) are conserved in the N terminus of MhpP for [2Fe-2S] cluster binding, and two other motifs (RXYS and GXXS/T) are conserved in the C terminus for binding the isoalloxazine and phosphate groups of flavin adenine dinucleotide (FAD). Two motifs (S/T-R and yXCGp) responsible for binding to reduce nicotinamide adenine dinucleotide phosphate (NADPH) are also conserved in MhpP, although some residues differ. To confirm the function of this reductase, MhpP was heterologously expressed in Escherichia coli BL21(DE3) and purified. UV-visible spectroscopy and electron paramagnetic resonance spectroscopy revealed that MhpP contains a [2Fe-2S] cluster. MhpP mutants in which the four cysteine residues were substituted via site-directed mutagenesis lost the ability to bind the [2Fe-2S] cluster, resulting in a decrease in enzyme-specific oxidation of NADPH. Thin-layer chromatography revealed that MhpP contains FAD. Substrate specificity analyses confirmed that MhpP uses NADPH rather than NADH as an electron donor. MhpP oxidizes NADPH using cytochrome c, potassium ferricyanide, or nitro blue tetrazolium as an electron acceptor, with a specific activity of 1.7 ± 0.36, 0.78 ± 0.13, and 0.16 ± 0.06 U/mg, respectively. Thus, S. acidophilus TPY MhpP is a novel NADPH-dependent reductase component of phenol hydroxylase that utilizes FAD and a [2Fe-2S] cluster as cofactors.     

Hydrothermal time analysis of watermelon (<Emphasis Type="Italic">Citrullus vulgaris</Emphasis> cv. ‘Crimson sweet’) seed germination

This study evaluated the ability of a hydrothermal time model (HTT) to describe the kinetics of watermelon (Citrullus vulgaris cv. ‘Crimson sweet’) seed germination under different temperatures (T) and water potentials (ψ) and also to determine the cardinal temperatures of watermelon. Results indicated that ψ influenced germination rate and germination percentage. For this seed lot, cardinal temperatures were 10 °C for T _b, 28.34 °C for T _o and 40.8 °C for T _c in the control (0 MPa) treatment. There was a decrease in hydrotime constant (θ _H) when T was increased to T _o and then remained constant at supra-optimal temperatures (30 MPah^?1). Also, at temperatures above T _o, ψ _b(50) values increased linearly with T. The k _T value (the slope of the relationship between ψ _b(50) and T exceeds T _o) of this seed lot was calculated as 0.076 MPa°Ch^?1. Results this study show that when the HTT model is applied, it can accurately describe ψ _b(g) and the course of germination around Ts (R ² = 0.82). Moreover, the ψ _b(50) was estimated to be ?0.96 MPa based on this model. Consequently, the germination response of watermelon for all Ts and ψs can be adequately described by the HTT model and enabling it to be used as a predictive tool in watermelon seed germination simulation models.     

Evaluation of ethanol production and bioadsorption of heavy metals by various red seaweeds

The objective of this study was to evaluate ethanol production and bioadsorption with four red seaweeds, Gelidium amansii, Gracilaria verrucosa, Kappaphycus alvarezii and Eucheuma denticulatum. To produce ethanol, thermal acid hydrolysis, enzymatic saccharification and fermentation was carried out. After pretreatment, 38.5, 39.9, 31.0 and 27.5 g/L of monosaccharides were obtained from G. amansii, G. verrucosa, K. alvarezii and E. denticulatum, respectively. Ethanol fermentation was performed with Saccharomyces cerevisiae KCCM 1129 adapted to 80 g/L galactose. The ethanol productions by G. amansii, G. verrucosa, K. alvarezii and E. denticulatum were 18.8 g/L with Y _EtOH = 0.49, 19.1 g/L with Y _EtOH = 0.48, 14.5 g/L with Y _EtOH = 0.47 and 13.0 g/L with Y _EtOH = 0.47, respectively. The waste seaweed slurries after the ethanol fermentation were reused to adsorb Cd(II), Pb(II) and Cu(II). Using langmuir isotherm model, Cu(II) had the highest affinity for waste seaweeds with the highest q _max and electronegativity values among three heavy metals.     

Better tolerance to water deficit in doubled diploid ‘Carrizo citrange’ compared to diploid seedlings is associated with more limited water consumption

Tolerance to water deficit in diploid (2x) and doubled diploid (4x) ‘Carrizo citrange’ (Citrus sinensis [L.] Osbeck × Poncirus trifoliata [L.] Raf) was investigated. Water deficit was applied for 4 weeks. Physiological parameters, including stomatal conductance (g _s), photosynthesis (A), transpiration (E), leaf and soil water potentials (Ψ _leaf; Ψ _soil), and pot water loss, were monitored throughout the stress. Moreover, ABA, H₂O₂ contents, and the expression of genes involved in ABA biosynthesis (NCED3), regulation of abscisic acid signaling (ABI1), and coding for a catalase enzyme (CAT2) known to favor H₂O₂ scavenging were monitored. During the experiment g _s, A, and E values were most of the time higher in 2x compared to 4x. During the water deficit period, pot water loss decreased faster in 2x compared to 4x, leading to a faster decrease in all physiological parameters in 2x. The higher sensitivity of 2x compared to 4x was correlated with more numerous thinner roots, higher leaf ABA and H₂O₂ contents, and with the lower leaf water potential. ABI1 and NCED3 expression was not strictly correlated with the ABA content. However, the higher CAT2 expression in 4x was correlated with the lower leaf H₂O₂ contents. Therefore, the better tolerance observed in 4x ‘Carrizo citrange’ compared to 2x was associated with more limited water consumption and better and H₂O₂ scavenging.     

Interacting effects of elevated atmospheric CO<Subscript>2</Subscript> and hydrology on the growth and carbon sequestration of <Emphasis Type="Italic">Sphagnum</Emphasis> moss

Peatlands are a critical carbon store comprising 30% of the Earth’s terrestrial soil carbon. Sphagnum mosses comprise up to 90% of peat in the northern hemisphere but impacts of climate change on Sphagnum mosses are poorly understood, limiting development of sustainable peatland management and restoration. This study investigates the effects of elevated atmospheric CO₂ (eCO₂) (800 ppm) and hydrology on the growth of Sphagnum fallax, Sphagnum capillifolium and Sphagnum papillosum and greenhouse gas fluxes from moss–peat mesocosms. Elevated CO₂ levels increased Sphagnum height and dry weight but the magnitude of the response differed among species. The most responsive species, S. fallax, yielded the most biomass compared to S. papillosum and S. capillifolium. Water levels and the CO₂ treatment were found to interact, with the highest water level (1 cm below the surface) seeing the largest increase in dry weight under eCO₂ compared to ambient (400 ppm) concentrations. Initially, CO₂ flux rates were similar between CO₂ treatments. After week 9 there was a consistent three-fold increase of the CO₂ sink strength under eCO₂. At the end of the experiment, S. papillosum and S. fallax were greater sinks of CO₂ than S. capillifolium and the ? 7 cm water level treatment showed the strongest CO₂ sink strength. The mesocosms were net sources of CH₄ but the source strength varied with species, specifically S. fallax produced more CH₄ than S. papillosum and S. capillifolium. Our findings demonstrate the importance of species selection on the outcomes of peatland restoration with regards to Sphagnum’s growth and GHG exchange.     

Theoretical study on <Emphasis Type="Italic">p</Emphasis>-type D-π-A sensitizers with modified π-spacers for dye-sensitized solar cells

Based on a prototype sensitizer W2, we designed triarylamine-based p-type sensitizers W2-1 to W2-7 that contain modified π-spacers (π'), a π-spacer and two anchors. For W2-1 to W2-4, instead of 2,1,3-benzothiadiazole in W2, thieno[3,4-b]-1,4-dioxin, thiophene, thieno[3,4-c][1,2,5]thiadizole, thiazolo[5,4-d]thiazole are π' and thiophene as π-spacer. For W2-5 to W2-8, π' and π are same, with 2,1,3-benzothiadiazole, thieno[3,4-b]-1,4-dioxin, thieno[3,4-c][1,2,5]thiadiazo, thiazolo[5,4-d]thiazole, respectively, as the π'-spacers. Structure optimization, electronic level and absorption characters were calculated with density functional theory (DFT) and time-dependent DFT (TDDFT) at the CAM-B3LYP/6-311G (d,p). The solvent effect was involved using a polarized continuum model in chloroform. The results showed that the highest occupied molecular orbital and the lowest unoccupied molecular orbital guarantee sufficient hole injection (lower than –0.2 eV), and dye regeneration (lower than –0.2 eV). W2-4 has higher light-harvesting efficiency (LHE) (0.994) and larger overlap with the visible light from 400 nm to 600 nm. Finally, the results suggest that the driving force of hole injection, dye regeneration and charge recombination (ΔG_inj, ΔG_reg and ΔG_CR) of W2-4 are the best, with more negative ΔG_inj (–4.33), ΔG_reg (–1.74) and more positive ΔG_CR (1.92). Replacing 2,1,3-benzothiadiazole with thiazolo[5,4-d]thiazole as π'-spacers is a effective way to improve the performance of the dyes. An introduction of thiazolo[5,4-d]thiazole group can improve the absorption ability and hinder charge recombination.

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Graphical abstract Absorption spectra of p-type D-π-A sensitizers with modified π-spacers