Electron Acceptor Research Articles

Enhancing biohydrogen production from xylose through natural FeS2 ore: Mechanistic insights

In this study, we investigated the advantages of utilizing natural FeS2 ore in the context of dark fermentative hydrogen production within a fermentation system employing heat-treated anaerobic granular sludge with xylose as the carbon source. The results demonstrated a significant improvement in both hydrogen production and the maximum rate, with increases of 2.58 and 4.2 times, respectively. Moreover, the presence of FeS2 ore led to a reduction in lag time by more than 2–3 h. The enhanced biohydrogen production performance was attributed to factors such as the intracellular NADH/NAD+ ratio, redox-active components of extracellular polymeric substances, secreted flavins, as well as the presence of hydrogenase and nitrogenase. Furthermore, the FeS2 ore served as a direct electron donor and acceptor during biohydrogen production. This study shed light on the underlying mechanisms contributing to the improved performance of biohydrogen production from xylose during dark fermentation through the supplementation of natural FeS2 ore.

Enhanced peroxymonosulfate activation by S-scheme AgI/Cu-BiVO4 heterojunction for efficient photocatalytic organics degradation and Microcystis aeruginosa inactivation: Performance, interfacial engineering and mechanism insight

Novel oxygen vacancies-enriched AgI/Cu-BiVO4 (ACBV) S-scheme heterojunction catalysts were constructed to boost photocatalytic organics degradation and M. aeruginosa inactivation with peroxymonosulfate (PMS) assistance. Specific interfacial charge transfer and abundant active centers were guided by introducing Cu doping and AgI coupling into BiVO4, with the catalytic activity and mechanism systematically investigated. The optimal 0.25-ACBV heterojunction exhibited 97.6% tetracycline (TC) degradation under PMS-assisted visible light and achieved effective inactivation of M. aeruginosa within 20 min (78.8%). The S-scheme heterostructure from Cu-BiVO4 to AgI and synergistic effects endowed the system with high-energy carrier transfer kinetics and strong oxygen reduction capability. Meanwhile, the redox cycling of Cu2+/Cu+ and surface oxygen defects served as electron acceptors to accelerate interfacial charge separation and as adsorption activation sites for PMS, promoting efficient mass transfer in the non-homogeneous system. This study inspires the design of high-performance S-scheme photocatalytic activators and expands their potential applications in environmental remediation.

Microbial communities outperform extracellular polymeric substances in the reduction of hexavalent chromium by anaerobic granular sludge

The reduction of hexavalent chromium [Cr(VI)] by microbiota agents is a potential method for ecological remediation in heavily contaminated soil. This study investigated the contribution of microbial community and extracellular polymeric substances (EPS) to reduce Cr(VI) using lab-cultured anaerobic granular sludge (AGS). The AGS demonstrated an impressive reduction efficiency of 99.3% for Cr(VI) in soil, operating within an initial Cr(VI) concentration range of 500–3000 mg/kg. The distribution of typical electron acceptors, e.g., SO42-, NO3-, and Fe3+, had a negligible influence on microbial Cr(VI) reduction. The contribution of EPS on Cr(VI) reduction accounted for only 2.1% of the total Cr(VI) reduction, implying that Cr(VI) reduction driven by AGS was primarily caused by the direct effect of microbiota. High-throughput sequencing analysis confirmed that an increasing trend in the relative abundance of Cr reduction bacteria (Sphingopyxis: 0.40–5.54%, Thermonas: 0.41–5.70%, Edaphobaculum: 0.35–6.64%, etc.), and the stability (0.716–4.114) of microbial co-occurrence networks was significantly promoted by the end of the experiment. Materials characterization indicated that successful reduction of Cr(VI) to trivalent chromium [Cr(III)] and formed in Cr(OH)3, and functional groups, O-H, N-H, -CH, and -CH2, of AGS likely played a vital role in Cr(VI) reduction. Overall, these findings offer insights into the remediation technique of microbial Cr(VI) reduction in highly-contaminated soil based on the interaction network stability of the microbial community in AGS.

Design of a Low‐Cost Electron Acceptor for Highly Efficient Organic Solar Cell through Alkyl Chain Branching Position Manipulation

The state‐of‐the‐art bulk‐heterojunction (BHJ) organic solar cells (OSCs) typically include expensive fused‐ring electron acceptors, hindering industrialization. Designing low‐cost and highly efficient electron acceptors remains challenging. Herein, two low‐cost electron acceptors (DTB2 and DTB3) based on a conjugated 1,4‐di(thiophen‐2‐yl)benzene (DTB) core and two fluorinated 2‐(3‐oxo‐2,3‐dihydroinden‐1‐ylidene)malononitrile end‐groups are reported. Their only difference is the alkyl chain branching position on the benzene ring. Both acceptors exhibit similar low optical gaps of ≈1.35 eV but different molecular orientations. DTB2 shows an edge‐on arrangement, while DTB3, with a shift in branching positions toward the conjugated backbone, produces a face‐on arrangement. Such molecular orientations are maintained in their BHJ layers after blending with a polymer donor PBQx‐TF. The PBQx‐TF:DTB3 film demonstrates superior BHJ phase‐separation and faster charge carrier generation (0.44 ps) than those of the PBQx‐TF:DTB2 film (50 ps). As a result, the DTB2‐based OSC achieves a modest power conversion efficiency (PCE) of 8.5%. While the DTB3‐based OSC produces an outstanding PCE of 15.3%, which is much higher than those of the reported DTB‐based OSCs. Besides, DTB3 has a figure of merit up to 0.46, higher than the state‐of‐the‐art fused‐ring electron acceptors. This work provides new insights into designing low‐cost and highly efficient electron acceptors.

Disclosing the intrinsic nature of efficient removal of antibiotics in N/S dual-doped porous carbon-based materials: The manipulation of internal electric field

N/S co-doping has emerged as a prevailing strategy for carbon-based adsorbents to facilitate the antibiotic removal efficiency. Nevertheless, the underlying interplay among N, S, and their adjacent vacancy defects remains overlooked. Herein, we present a novel in situ strategy for fabricating pyridinic-N dominated and S dual-doped porous carbon adsorbent with rich vacancy defects (VNSC). The experimental results revealed that N (acting as the electron donor) and S (acting as the electron acceptor) form an internal electric field (IEF), with a stronger IEF generated between pyridinic-N and S, while their adjacent vacancy defects activate carbon π electrons, thus enhancing the charge transfer of the IEF. Density functional theory (DFT) calculations further demonstrated that the rich charge transfer in the IEF facilitated the π-π electron donor-acceptor (EDA) interaction between VNSC and tetracycline (TC) as well as norfloxacin (NOR), and thus is the key to adsorption performance of VNSC. Consequently, VNSC exhibited high adsorption capacities toward TC (573.1 mg g−1) and NOR (517.0 mg g−1), and its potential for environmental applications was demonstrated by interference, environmentally relevant concentrations, fixed-bed column, and regeneration tests. This work discloses the natures of adsorption capacity for N/S dual-doped carbon-based materials for antibiotics.

Long-Lived Charge Separation in Single Crystals of an Electron Donor Covalently Linked to Four Acceptor Molecules.

Crystalline donor-acceptor (D-A) systems serve as an excellent platform for studying CT exciton creation, migration, and dissociation into free charge carriers for solar energy conversion. Donor-acceptor cocrystals have been utilized to develop an understanding of CT exciton formation in ordered organic solids; however, the strong electronic coupling of the D and A units can sometimes limit charge separation lifetimes due to their close proximity. Covalent D-A systems that preorganize specific donor-acceptor structures can assist in engineering crystal morphologies that promote long-lived charge separation to overcome this limitation. Here we investigate photogenerated CT exciton formation in a single crystal of a 2,5,8,11-tetraphenylperylene (PerPh4) donor to which four identical naphthalene-(1,4:5,8)-bis(dicarboximide) (NDI) electron acceptors are covalently attached at the para positions of the PerPh4 phenyl groups to yield PerPh4-NDI4. X-ray crystallography shows that the four NDIs pack pairwise into two distinct motifs. Two NDI acceptors of one PerPh4-NDI4 are positioned over the PerPh4 donors of adjacent PerPh4-NDI4 molecules with the donor and acceptor π-systems having a large dihedral angle between them, while the other two NDIs of PerPh4-NDI4 form xylene-NDI van der Waals π-stacks with the corresponding NDIs in adjacent PerPh4-NDI4 molecules. Upon selective photoexcitation of PerPh4 in the single crystal, CT exciton formation occurs in <300 fs yielding electron-hole pairs that live for more than ∼16 μs. This demonstrates the effectiveness of covalently linked D-A systems for engineering single crystal structures that promote efficient and long-lived charge separation for solar energy conversion.

Exploring Efficient Blue TADF Materials with Ultrafast Bipolar Charge Transport for High‐Efficiency Thick‐Layer OLEDs

AbstractAchieving strong solid‐state photoluminescence and fast charge transport simultaneously for organic molecules is of significant importance but challenging because of the trade‐off between these properties. Herein, two tailored blue luminescent molecules constructed with ring‐fused carbonyl‐containing electron acceptors and spiro‐acridine electron donors are developed. Owing to ordered long‐range molecular alignment with proper interaction energies, their neat films exhibit ultrafast bipolar charge transport and strong delayed fluorescence with high quantum yields and short lifetimes. In doped organic light‐emitting diodes (OLEDs), both molecules display eminent electroluminescence performances with excellent external quantum efficiencies (EQEs) of 40.6%. They also exhibit brilliant blue lights with record‐beating EQEs of 30.2% in non‐doped thin‐layer OLEDs, and more importantly, high‐performance simplified non‐doped thick‐layer OLEDs are achieved, rendering lowered driving voltages, and the best EQEs of 23.0% with tiny efficiency roll‐offs. In addition, using them as sensitizers, remarkable EQEs of 40.1% and 23.2% with ultrasmall efficiency roll‐offs are realized in blue hyperfluorescence thin‐layer and thick‐layer OLEDs, respectively. The operational lifetimes are obviously elongated matter in non‐doped thick‐layer devices or hyperfluorescence thick‐layer devices. This work provides promising candidates for efficient simplified thick‐layer OLEDs and opens a new avenue toward organic molecules with strong delayed fluorescence and fast charge transport simultaneously.

The Tsai vs. Bergman Cluster Stability in ZnMgSc 1/1 Periodic Approximant Crystal

AbstractQuasicrystals with icosahedral symmetry can be classified into two main groups: Bergman‐type and Tsai‐type. While these are considered as distinct phases, they share a common feature of being constructed from atomic clusters, either Tsai or Bergman. In this study, we employ Density Functional Theory to perform electronic structure calculations on the Zn84.79Mg0.86Sc14.35 periodic approximant crystal phase. Our investigation involves systematically displacing atoms from Tsai cluster sites to Bergman cluster sites, allowing us to explore modifications in the electronic structure. Our findings reveal that the stability of the phase is influenced by the interaction between Zn‐4p and Sc‐3d orbitals. We observe that the sp‐d hybridization effect may play a more crucial role rather than Hume‐Rothery stabilization, as this observation holds true regardless of the presence or absence of periodic boundary conditions. Notably, the additional atom present in the Tsai structure serves as a significant electron acceptor in low‐energy orbitals. Its absence in Bergman structures results in a composition with fewer atoms possessing high‐energy d orbitals. This discovery provides a rationale for the frequent occurrence of Bergman phases with transition metals or rare earth elements, which occupy less than 10 % of the sites in the structure.

Complex I activity in hypoxia: implications for oncometabolism.

Certain cancer cells within solid tumors experience hypoxia, rendering them incapable of oxidative phosphorylation (OXPHOS). Despite this oxygen deficiency, these cells exhibit biochemical pathway activity that relies on NAD+. This mini-review scrutinizes the persistent, residual Complex I activity that oxidizes NADH in the absence of oxygen as the electron acceptor. The resulting NAD+ assumes a pivotal role in fueling the α-ketoglutarate dehydrogenase complex, a critical component in the oxidative decarboxylation branch of glutaminolysis - a hallmark oncometabolic pathway. The proposition is that through glutamine catabolism, high-energy phosphate intermediates are produced via substrate-level phosphorylation in the mitochondrial matrix substantiated by succinyl-CoA ligase, partially compensating for an OXPHOS deficiency. These insights provide a rationale for exploring Complex I inhibitors in cancer treatment, even when OXPHOS functionality is already compromised.

Boron nitride doped with transition metals for carbon monoxide detection: a promising nanosensor for air cleaning

PurposeThis study aims to investigate the potential of the decorated boron nitride nanocage (BNNc) with transition metals for capturing carbon monoxide (CO) as a toxic gas in the air.Design/methodology/approachBNNc was modeled in the presence of doping atoms of titanium (Ti), vanadium (V), chromium (Cr), cobalt (Co), copper (Cu) and zinc (Zn) which can increase the gas sensing ability of BNNc. In this research, the calculations have been accomplished by CAM–B3LYP–D3/EPR–3, LANL2DZ level of theory. The trapping of CO molecules by (Ti, V, Cr, Co, Cu, Zn)–BNNc has been successfully incorporated because of binding formation consisting of C → Ti, C → V, C → Cr, C → Co, C → Cu, C → Zn.FindingsNuclear quadrupole resonance data has indicated that Cu-doped or Co-doped on pristine BNNc has high fluctuations between Bader charge versus electric potential, which can be appropriate options with the highest tendency for electron accepting in the gas adsorption process. Furthermore, nuclear magnetic resonance spectroscopy has explored that the yield of electron accepting for doping atoms on the (Ti, V, Cr, Co, Cu, Zn)–BNNc in CO molecules adsorption can be ordered as follows: Cu > Co >> Cr > Zn ˜ V> Ti that exhibits the strength of the covalent bond between Ti, V, Cr, Co, Cu, Zn and CO. In fact, the adsorption of CO gas molecules can introduce spin polarization on the (Ti, V, Cr, Co, Cu, Zn)–BNNc which specifies that these surfaces may be used as magnetic-scavenging surface as a gas detector. Gibbs free energy based on IR spectroscopy for adsorption of CO molecules adsorption on the (Ti, V, Cr, Co, Cu, Zn)–BNNc have exhibited that for a given number of carbon donor sites in CO, the stabilities of complexes owing to doping atoms of Ti, V, Cr, Co, Cu, Zn can be considered as: CO →Cu–BNNc >> CO → Co–BNNc > CO → Cr–BNNc > CO → V–BNNc > CO → Zn–BNNc > CO → Ti–BNNc.Originality/valueThis study by using materials modeling approaches and decorating of nanomaterials with transition metals is supposed to introduce new efficient nanosensors in applications for selective sensing of carbon monoxide.

Uncovering the role of oxygen on organic carbon cycling: insights from a continuous culture study with a facultative anaerobic bacterioplankton species (Shewanella baltica)

Deoxygenation is tied to organic carbon (Corg) supply and utilization in marine systems. Under oxygen-depletion, bacteria maintain Corg respiration using alternative electron acceptors such as nitrate. Since anaerobic respiration’s energy yield is lower, Corg remineralization may be reduced and its residence time increased. We investigated the influence of oxygen and alternative electron acceptors’ availability on Corg cycling by heterotrophic bacteria during a continuous culture experiment with Shewanella baltica, a facultative anaerobic γ-Proteobacteria in the Baltic Sea. We tested six different oxygen levels, from suboxic (&amp;lt;5 µmol L-1) to fully oxic conditions, using a brackish (salinity=14 g L-1) media supplied with high (HighN) or low (LowN) inorganic nitrogen concentrations relative to glucose as labile Corg source. Our results show that suboxia limited DOC (glucose) uptake and cell growth only under LowN, while higher availability of alternative electron acceptors seemingly compensated oxygen limitation under HighN. N-loss was observed under suboxia in both nitrogen treatments. Under HighN, N-loss was highest and a C:N loss ratio of ~2.0 indicated that Corg was remineralized via denitrification. Under LowN, the C:N loss ratio under suboxia was higher (~5.5), suggesting the dominance of other anaerobic respiration pathways, such as dissimilatory nitrate reduction to ammonium (DNRA). Bacterial growth efficiency was independent of oxygen concentration but higher under LowN (34 ± 3.0%) than HighN (26 ± 1.6%). Oxygen concentration also affected dissolved organic matter (DOM) cycling. Under oxic conditions, the release of dissolved combined carbohydrates was enhanced, and the amino acid-based degradation index (DI) pointed to more diagenetically altered DOM. Our results suggest bacterial Corg uptake in low-oxygen systems dominated by S. baltica can be limited by oxygen but compensated by high nitrate availability. Hence, suboxia diminishes Corg remineralisation only when alternative electron acceptors are lacking. Under high nitrate:Corg supply, denitrification leads to a higher N:C loss ratio, potentially counteracting eutrophication in the long run. Low nitrate:Corg supply may favour other anaerobic respiration pathways like DNRA, which sustains labile nitrogen in the system, potentially intensifying the cycle of eutrophication. Going forward, it will be crucial to establish the validity of our findings for S. baltica in natural systems with diverse organic substrates and microbial consortia.

Rational fabrication of Z-scheme heterojunction ZnFe2O4-seed@TpTt-COF for the visible-light-driven photocatalytic degradation of bisphenol A in food waste leachate boosted by primitive humic acid

Herein, we proposed a method by pre-embedding organic covalent organic framework TpTt-COF(TpTt) (consisting of the electron donor 1,3,5-triazine-2,4,6-triamine (Tt) and electron acceptor 2,4,6-triformylphloroglucinol (Tp) aldehyde) within inorganic ZnFe2O4 core to serve as seed for the in-situ grafting of organic TpTt shell tightly. The as-formed ZnFe2O4-seed@TpTt-COF (Z-S@TpTt) core–shell structure exhibited visible-light-driven photocatalytic degradation of BPA effectively. This may stem from the rationally tuned energy band structure of ZnFe2O4-seed via TpTt pre-anchoring, thus enabled a Z-scheme electron transfer way within the heterojunction to broaden the light adsorption, accelerate the charge transfer and maintain their thermodynamic redox capacity. More strikingly, humic acid (HA) in the actual wastewater (food waste leachate (FWL), where BPA highly frequently presented) could even boost the photocatalytic degradation of BPA. Comprehensive characterizations and DFT calculations revealed that HA acts as a critical “electron shuttle” to further promote the separation of electron-hole pairs via the formation of an EDA complex with the Z-S@TpTt. The gathered electrons on CB of ZnFe2O4-seed and holes on VB of TpTt may generate more •O2– and 1O2, thus the improved performance of Z-S@TpTt core–shell heterojunction in BPA degradation was achieved. Besides the promoted catalytical activity, the convenient separation ability and extraordinary chemical/thermal stability inherited from the magnetic core and the COF shell also enabled robust reuse of Z-S@TpTt heterojunction in FWL. All of these properties endowed Z-S@TpTt heterojunction with the practical application potential to remove BPA in an economical and environment-friendly way, which is also compatible with the “waste control by waste” strategy today.

Theoretical assessment of discharge effects on the decomposition tendency of C6F12O over metallic surfaces

AbstractC6F12O is proposed to be one potential eco‐friendly insulation gas to replace SF6. However, the assessment of its decomposition properties and the compatibility with metal electrodes in discharge faults is still challenging, which greatly hinders the development of its insulation and arc‐extinction applications. Herein, a theoretical method is proposed to reasonably address the discharge effects on C6F12O decomposition over typical Cu and Al electrodes at atomic scale. The results show that both the external electric field and the excess electrons could affect the activation of C6F12O by changing the electron acceptance of C6F12O and the orbital hybridisation during the surface bonding. On metal surfaces, the C‐F single bond in adsorbed C6F12O is the weakest position to decompose, and its cleavage could be promoted by the discharge effects. After the C‐F breaking, the C‐C cleavage remains unfavourable on Cu (111), but it is significantly promoted on Al (111), indicating a higher corrosion risk on the Al surface via continuous C6F12O decompositions. The proposed method as a valid supplement to the experiment reveals the discharge effects and the decomposition tendency of C6F12O on metal electrodes in discharge faults, which broadens the means for insulation gas evaluation.

Far-Red to Near-Infrared Emission from Conjugated Polymers with High Density of Excited States Based on a Boron Tropolonate Complex as an Electron Acceptor

Far-Red to Near-Infrared Emission from Conjugated Polymers with High Density of Excited States Based on a Boron Tropolonate Complex as an Electron Acceptor

The Effect of Position of Cyano-3-Acetic Acid Electron Withdrawing Group on γ-Mangostin as a Sensitizer on Dye-Sensitized Solar Cells (DSSC): Theoretical Study

Computational research on the influence of the electron acceptor group position of cyano-3-acetic acid on γ-mangostin as a sensitizer in Dye-Sensitized Solar Cell (DSSC) has been carried out with variations in the positions of the atoms O-1, O-2, O-3 and O- 4. The photoelectric properties are known from the HOMO-LUMO energy parameters, UV-Vis absorption, |VRP|, ΔGinject, ΔGreg, τ, LHE and FEDAM. Geometry optimization uses Orca 4.2.1 with a 6-31G* basis set and interpretation uses Avogadro, Chemissian and GaussSum. Ground state optimization uses the DFT-B3LYP method and excited state optimization uses the TD-DFT-B3LYP method. The results showed that the difference in photoelectric properties affected the DSSC performance. O-2 has the best parameters for electron scattering and UV-Vis light with an absorption of 426 nm. O-3 has the best value for excited state lifetime (τ) and coupling constant (|VRP|). O-3 has a weakness in the LHE value. The LHE value for compounds without modification has the best value. Based on the qualitative parameters of the Full-Electron Donor-Acceptor Map (FEDAM) it was found that the ability of cyano-3-acetic acid as an electron acceptor is better at O-2.

Enhancing in situ biodegradation in groundwater using pump and treat remediation: a proof of concept and modelling analysis of controlling variables.

A remediation approach which uses pump and treatment (PAT) to enhance the biodegradation of organic contaminants by increasing dispersive mixing between plumes and groundwater was evaluated for a phenol-contaminated aquifer, using a reactive transport model which simulates kinetic reactions between an electron donor (ED) in the plume and electron acceptor (EA) in the groundwater. The influence of system design and operation was examined in six modelling scenarios. Injection or extraction of groundwater increases biodegradation above no action and the location, pumping rate, and distance between well(s) are important variables which influence biodegradation. An increase in pumping rate, distance of the wells from the plume centreline, and changing the flow direction increase dispersive mixing between the plume and groundwater. This increases plume spreading and the plume fringe interface, providing a greater flux of dissolved EAs for biodegradation. In general, injection of groundwater containing natural EAs enhances biodegradation more than extraction. The enhancement of biodegradation is sensitive to the relative fluxes of ED and EA, as controlled by the arrangement of the wells. In the best performing scenario, biodegradation was enhanced by 128%, compared with no action.

Invasive weed of Eupatorium Adenophora Spreng leaves extract as a novel efficient inhibitor for the corrosion of cold rolled steel in chloroacetic acid solution

Traditional inhibitors are restricted due to their high price and high toxicity. Plant extracts as green inhibitors can be used as an alternative to traditional inhibitors due to their merits of low price, eco-friendly, and rich resources. The inhibitive action and mechanism of Eupatorium Adenophora Spreng leaves extract (EASLE) on the corrosion of cold rolled steel (CRS) in chloroacetic acid (ClCH2COOH) medium was investigated for the first time. The maximum inhibition efficiency of EASLE is 94.9% even at higher temperature of 50 °C. The surface micro-topography of inhibited CRS is relatively flat from SEM, AFM and CLSM images, and C/N/O elements contained in EASLE can form coordinated bonds with Fe atoms, as observed through XPS and TOF-SIMS. The adsorption of EASLE mainly occurs through chemisorption and is consistent with Langmuir isotherm. EASLE acts as a hybrid inhibitor, and its inhibitive mechanism is consistent with “geometric blocking effect”. The charge-transfer resistance turns to be higher after adding EASLE, and there is a single time constant. All the main inhibiting components of o-cresol, erucamide, vanillin, 3-phenoxybenzoic acid, p-coumaric acid, and adenine in EASLE exhibit the inhibition efficiency of approximately 80% in ClCH2COOH. Theoretical calculations suggest that benzene rings, heterocycles, and carboxyl groups are derived from these active components can be used as both electron acceptors and provider. The hydrophilic group can actively adsorb to CRS surface through heteroatoms of erucamide, while the hydrophobic group with a long carbon chain extends to the aqueous phase to form a protective barrier. EASLE can be an excellent substitute for traditional inhibitors, which are of both economic and environmental values.

Enzymatic synthesis of a skin active ingredient - glochidone by 3-ketosteroid dehydrogenase from Sterolibacterium denitrificans

In this study, we applied AcmB2, sourced from Sterolibacterium denitrificans, to catalyze the oxidative dehydrogenation of 3-ketolupeol (lupenone), a derivative of lupeol, triterpene obtained from birch bark. This enzymatic Δ1-dehydrogenation catalyzed by AcmB2 yielded glochidone, a bioactive compound frequently obtained from medicinal plants like Salvia trichoclada and Maytenus boria. Glochidone is known for its broad biological activities, including antibacterial, antifungal, anti-inflammatory, anticancer, antidiabetic as well as acetylcholinesterase inhibition. Our research demonstrates >99% conversion efficiency with 100% regioselectivity of the reaction. The effective conversion to glochidone employed an electron acceptor e.g., potassium hexacyanoferrate III, in mild, environmentally friendly conditions: 8–16% 2-hydroxypropyl-β-cyclodextrin, and 2–3% 2-methoxyethanol. AcmB2 reaction optimum was determined at pH 8.0 and 30 °C. Enzyme's biochemical attributes such as electron acceptor type, concentration and steroid substrate specificity were investigated. Among 4-, 5- and 6-ring steroid derivatives androst-4-en-3,17-dione and testosterone propionate were determined as the best substrates of AcmB2. Δ1-Dehydrogenation of substrates such as lupenone, diosgenone and 3-ketopetromyzonol was confirmed. We have assessed the antioxidant and rejuvenating characteristics of glochidone as an active component in formulations, considering its precursors, lupeol, and lupenone as well. Glochidone exhibited limited antioxidant and chelating capabilities compared to lupeol and reference compounds. However, it demonstrated robust rejuvenating properties, with a sirtuin induction level of 61.5 ± 1.87%, notably surpassing that of the reference substance, E-resveratrol (45.15 ± 0.09%). Additionally, glochidone displayed 26.5±0.67 and 19.41±0.76% inhibition of elastase and collagenase, respectively. The safety of all studied triterpenes was confirmed on skin reconstructed human Epidermis model. These findings provide valuable insights into the potential applications of glochidone in formulations aimed at addressing skin health concerns. This research presents the first example of an enzyme in the 3-ketosteroid dehydrogenase (KstD) family catalyzing the Δ1-dehydrogenation of a pentacyclic triterpene. We also explored structural differences between AcmB, AcmB2, and related KstDs pointing to G52 and P532 as potentially responsible for the unique substrate specificity of AcmB2. Our findings not only highlight the enzyme's capabilities but also present novel enzymatic pathways for bioactive compound synthesis.

Assessing energy fluxes and carbon use in soil as controlled by microbial activity - A thermodynamic perspective A perspective paper

Soil organic matter (SOM) plays a central role for both the C cycle and soil functions. Plants provide the input and heterotrophic (micro)organisms are essential for the turnover. Microbial metabolism links matter and energy fluxes and generates the highest energy turnover dynamics in SOM because the organisms need both energy and matter for maintenance and growth. In this perspectives paper, we evaluate the knowledge on thermodynamic approaches potentially applicable to study the turnover of organic matter in the soil system. Thermodynamics is essential for understanding organic matter turnover in soil as turnover and storage are controlled by the energy supply to, and consumption by, microbes. Instead of just comparing the heat of combustion of compounds without considering microbial anabolism, we need to apply conventional thermodynamic state variables that can be either estimated using established thermodynamic equations, or measured empirically in soil. In particular, we can follow and quantify overall changes of enthalpies by calorimetry. Here, we suggest to apply a thermodynamic concept with the related experimental approaches of calo(respiro)metry and turnover mass balances including biomass formation. This enables us to better interpret and understand the highly variable carbon use efficiency (CUE) in a multi-substrate system such as soil and to relate this to energy use efficiency (EUE). Combining the experimental measurements of the thermodynamic state variables with mass turnover data allow prediction of whether compounds can be metabolized with energy delivery to microorganisms, or be thermodynamically stabilized under the respective redox and electron acceptor conditions. Energy balancing shows how much energy is actually used and retained in the soil, how much is emitted as heat, and how much may be stabilized due to endergonic turnover reactions. Thermodynamic stabilization should therefore be considered as basic stabilization process for organic compounds in soil.

Promoting denitrification via high electron conversion ratio in the iron valence Cycle: Prospects for Pseudomonas sp. JM-7 application in environmental engineering

The interdependence between iron and nitrogen in the environment is of utmost importance, and this study has explored the intricate relationship between denitrification and iron valence cycling using Pseudomonas sp. strain JM-7 (P. JM-7) as a model bacteria. Our research demonstrated that P. JM-7 had the ability to effectuate electron transfer from the periplasmic space to electron acceptors, such as nitrate, via Cytochrome c-proteins (c-Cyts). We found that iron valence state transformations with Fe(II)/Fe(III) promoted P. JM-7′s denitrification of nitrate coupled to yeast extract powder (YEP) oxidation. Denitrification rates depended on temperature (>21 °C) and pH (6–9). During logarithmic growth, 5 g/L YEP enabled 350 mg/L nitrate removal, increasing to 1650 mg/L in stable growth. Addition of 4 mM Fe(II)/Fe(III) increased denitrification to 500 mg/L during logarithmic growth. The dynamic test results displayed that compared to the SiO2 filler control group, iron-containing fillers could facilitate P. JM-7 to reduce 100 mg/L nitrate with 50 mg/L YEP electrons, corresponding to 6 times the maximum electron transfer efficiency in the static test. Overall, iron redox cycling significantly enhanced P. JM-7 denitrification, imparting insights into iron–nitrogen interactions. In summary, our research imparts valuable insights into the nexus between iron and nitrogen in the environment, highlighting the potential application of P. JM-7 in environmental engineering. Our findings indicate that P. JM-7 exhibits a significant denitrification capability, and further research is recommended to investigate its ability to remove phosphorus and promote sustainable environmental remediation practices.