A high H_2 evolution rate under visible light of a CdS/TiO_2@Ni S catalyst due to a directional electron transfer between the phases

The photocatalytic activity of CdS can be greatly improved by co-modification of NiS and TiO_2 materials; furthermore the order of connection affects much. A directional electron transfer route via CdS → TiO_2→ NiS is found crucial to the enhancement of ternary catalyst, where TiO_2 acts as an electron reservoir and Ni S works as an effective cocatalyst. Cd S/TiO_2@Ni S with Ni S loaded on TiO_2 has an activity of H_2 evolution 2.5 times higher than NiS@Cd S/TiO_2 with Ni S pre-loaded on Cd S. Faster e-/h+separation rates is obtained of Cd S/TiO_2@Ni S under visible light than under extra UV light irradiation, which in turn demonstrates the importance of directional electron transfer route.

Direct Electron－transfer Reaction of Cytochrome C at a Bare Spectrographic Graphite Electrode

he electrochemistry of cytochrome C was investigated at a spectrographicgraphite electrode. In phosphate buffer solution (pH= 7. 0) , cytochrome C showedstable and quasi-reversible response. The formal potential E￣(o') was 0. 015 V (at25℃ , vs. SCE) and the heterogeneous electron transfer rate constant k_s obtainedvaried form 1. 10×10￣(-3) cm · s￣(-1) to 1. 80k×10￣(-3) cm · s￣(-1). The thermodynamic pa-rameters of the electron transfer reaction of cvtochrome C was also estimated. Fur-thermore, the effect of the various electrode surface states on the electrochemistryof cytochrome C was discussed.

Direct Electron Transfer Reactions of Glucose Oxidase and D-Amino Acid Oxidase at a Glassy Carbon Electrode in Organic Media

Cyclic voltammetry is employed to demonstrate feasibility of direct electron transfer of glucose oxidase and D amino acid oxidase at a glassy carbon electrode in organic media. The reversible slight conformational change of glucose oxidase is observed by changing 0.1 mol/L phosphate buffer to acetonitrile containing 10% v/v of water and 0.05 mol/L tetrabutyalammonium perchlorate, and vice versa.

Coupling biomass pretreatment for enzymatic hydrolysis and direct biomass-to-electricity conversion with molybdovanadophosphoric heteropolyacids as anode electron transfer carriers

Owing to their acidity,oxidizing ability and redox reversibility,molybdovanadophosphoric heteropolyacids(H_(n+3)PMo_(12-n)VnO40,abbreviated as PMo_(12-n)Vn) were employed as electron transfer carriers for coupling biomass pretreatment for enzymatic hydrolysis and direct biomass-to-electricity conversion.In this novel coupled process,PMo_(12-n)Vn pretreatment that causes deconstruction of cell wall structure with PMo_(12-n)Vn being simultaneously reduced can be considered as the "charging" process.The reduced PMo_(12-n)Vn are further re-oxidized with release of electrons in a liquid flow fuel cell(LFFC) to generate electricity is the "discharging" process.Several Keggin-type PMo_(12-n)Vn with different degree of vanadium substitution(DSV, namely n) were prepared.Compared to Keggin-type phosphomolybdic acid(PMo_(12)),PMo_(12-n)Vn(n=1-6) showed higher oxidizing ability but poorer redox reversibility.The cellulose enzymatic digestibility of PMo_(12-n)Vn pretreated wheat straw generally decreased with increase in DSV, but xylan enzymatic digestibility generally increased with DSV.PMo_(12) pretreatment of wheat straw at 120℃ obtained the highest enzymatic glucan conversion(EGC) reaching 95%,followed by PMo11V1 pretreatment(85%).Discharging of the reduced heteropolyacids in LFFC showed that vanadium substitution could improve the maximum output power density(Pmax).The highest Pmax was obtained by PMo9 V3(44.7 mW/cm^(2)) when FeCl_(3) was used as a cathode electron carrier,while PMo_(12) achieved the lowest Pmax(27.4 mW/cm^(2)).All the heteropolyacids showed good electrode Faraday efficiency(>95%) and cell discharging efficiency(>93%).The energy efficiency of the coupled process based on the heat values of the products and generated electric energy was in the range of 18%-25% depending on DSV.PMo_(12) and PMo11V1 seem to be the most suitable heteropolyacids to mediate the coupled process.

Electrically conductive nanowires controlled one pivotal route in energy harvest and microbial corrosion via direct metal-microbe electron transfer

Extracellular electron transfer(EET)plays a critical role in bioelectrochemical processes,allowing cou-pling between microorganisms and extracellular solid-state electrodes,metals,or other cells in energy metabolism.Previous studies have suggested a role for outer-surface c-type cytochromes in direct metal-to-microbe electron transfer by Geobacter sulfurreducens,a model electroactive bacterium.Here,we ex-amined the possibility of other microbially produced electrical contacts by deleting the gene for PilA,the protein monomer that G.sulfurreducens assembles into electrically conductive protein nanowires(e-pili).Deleting pilA gene inhibited electron extraction from pure iron and 316L stainless steel up to 31%and 81%,respectively more than deleting the gene for the outer-surface cytochrome OmcS.This PilA-deficient phenotype,and the observation that relatively thick biofilms(21.7μm)grew on the metal surfaces at multi-cell distances from the metal surfaces suggest that e-pili contributed significantly to microbial cor-rosion via direct metal-to-microbe electron transfer.These results have implications for the fundamental understanding of electron harvest via e-pili by electroactive microbes,their uses in bioenergy production,as well as in monitoring and mitigation of metal biocorrosion.

Combined pretreatment using CaO and liquid fraction of digestate of rice straw: Anaerobic digestion performance and electron transfer

To improve anaerobic digestion(AD)efficiency of rice straw,solid alkaline CaO and the liquid fraction of digestate(LFD)were used as pretreatment agents of rice straw.The results showed that AD performance of rice straw with CaOLFD pretreatment was optimal in different pretreatment methods of the CaO+LFD,CaOLFD,LFD+CaO,CaO,and LFD.The maximum methane yield(314 ml(g VS)^(-1))and the highest VFAs concentration(14851 mg·L^(-1) on day 3)of the CaOLFD pretreatment group were 81%and 118%higher than that of the control group,respectively.Under the action of solid alkaline CaO,the bacteria of Clostridium,Atopostipes,Sphaerochaeta,Tissierella,Thiopseudomonas,Rikenellaceae,and Sedimentibacter could build up co-cultures with the archaeal of Methanosaeta,Methanobacterium,and Methanosarcina performing direct interspecies electron transfer(DIET)and improving AD performance of rice straw.Therefore,the combined pretreatment using CaO and LFD could not only pretreat rice straw but also stimulate co-cultures of microorganism to establish DIET enhancing AD efficiency.

改善剩余污泥厌氧消化产甲烷性能的新策略:导电材料介导微生物种间直接电子传递

综述了近年来关于碳基和铁基导电材料促进DIET产甲烷的研究进展,归纳了直接种间电子传递的机制,总结了碳基和铁基导电材料的结构特征、电子传递机理和强化剩余污泥厌氧产甲烷效果。指出了当前研究存在的不足,并对未来的研究方向做出了展望。

A direct electrochemical biosensor for rapid glucose detection based on nitrogen-doped carbon nanocages

Given the increasing number of diabetic patients,rapid and accurate detection of glucose in body fluids is critical.This study developed a direct electrochemical biosensor for glucose based on nitrogen-doped carbon nanocages(NCNCs).NCNCs possess a large specific surface area of 1395 m^(2)·g^(-1),a high N atomic content of 9.37%and good biocompatibility,which is favorable for enzyme loading and electron transfer.The surface average concentration of electroactive glucose oxidase on NCNCs was 2.82×10^(-10)mol·cm^(-2).The NCNC-based direct electrochemical biosensor exhibited a high sensitivity of 13.7μA·(mmol·L^(-1))^(-1)·cm^(-2),rapid response time of 5 s and an impressive electron-transferrate constant(ks)of 1.87 s^(-1).Furthermore,we investigated an NCNC-based direct electron transfer(DET)biosensor for sweat glucose detection,which demonstrated tremendous promise for non-invasive wearable diabetes diagnosis.

Electron transfer to direct oxidation of aqueous organics by perovskites

The residual of oxidant chemicals in advanced oxidation processes(AOPs)resulted in both economic cost and secondary pollution.Herein,we report a direct oxidation of phenolic pollutants induced by Ca-Mn-O perovskites without using an oxidant.Governed by one-electron transfer process(ETP)from the phenolics to the Ca-Mn-O perovskites,this direct oxidation proceeds in fast reaction kinetics with activation energy of 51.4 kJ/mol,which was comparable with those AOPs-based catalytic systems.Additionally,mineralization and polymerization reactions occurred on the Ca-Mn-O surface and ensured the complete removal of phenolics.The high spin state Mn(III)within Ca-Mn-O structure was the dominant active site for this ETP.The elongated axial Mn(III)–O bonds within the[MnO_(6)]octahedron facilitated the acceptance of the electrons from the phenolics and thus promoted the initiation of the direct oxidation process.Mn(III)in the high spin state can also activate dissolved O_(2)to produce singlet oxygen(^(1)O_(2))for a fast removal of phenolics.The mixed Mn(III)/Mn(IV)within Ca-Mn-O accelerated the ETP by enhancing the electrical conductivity.This efficient Ca-Mn-O-induced ETP for removal of organic contaminants casts off the dependence on external chemical and energy inputs and provides a sustainable approach for transforming the toxic organic pollutants into value-added polymers.

乙醇发酵预处理耦合生物炭强化城镇有机固废厌氧产甲烷

当前厌氧消化的核心技术原理是种间氢传递(IHT),其对扩散传质依赖高,在处理城镇有机固废(MOSW,主要包括餐厨垃圾和剩余污泥)时易受阻,导致厌氧产甲烷停滞。直接种间电子传递(DIET)对扩散传质依赖低,可取代IHT,成为城镇有机固废厌氧产甲烷的主要工作模式。乙醇型发酵预处理和投加碳基导电材料是促进厌氧消化中DIET的两大手段。以实际城镇有机固废为底物,采用乙醇型发酵预处理耦合生物炭的方法,对强化厌氧产甲烷性能进行探究。结果显示:(1)通过优化酿酒酵母培养时间、接种比及培养基组成,获得了酿酒酵母的最佳培养条件(培养时间为21.17 h,接种比为15%,每30 mL液体培养基组成为3.00 g葡萄糖、0.12 g蛋白胨、0.12 g酵母浸出粉及微量元素);(2)通过优化乙醇型发酵预处理的温度和酿酒酵母的接种比,获得了乙醇型发酵预处理的最佳工艺条件(最佳发酵温度为37℃,酿酒酵母接种比为20 mL/L);(3)设计半连续流厌氧消化实验,探究乙醇型发酵预处理耦合生物炭对城镇有机固废甲烷产量和底物去除的影响。相比于对照组,乙醇型发酵预处理(接种20 mL/L酿酒酵母)耦合生物炭(2 g/L)组的甲烷产量提高了102.50%,底物去除率提高了16.15%;(4)微生物群落分析发现,乙醇型发酵预处理耦合生物炭提高了Methanosaeta的相对丰度。优化了酿酒酵母的培养条件,确定了乙醇型发酵预处理的最佳温度和接种比,降低了经济成本。通过乙醇型发酵预处理耦合生物炭,构建了厌氧消化中DIET,强化了厌氧产甲烷,提高了城镇有机固废的资源化和减量化。

煤微生物甲烷化的石墨烯强化机制

强化煤制微生物甲烷的研究备受重视,是煤层气的一项有效增产措施。向发酵系统中添加导电材料可以有效促进直接种间电子传递提高甲烷产率,在强化有机物厌氧降解方面潜力巨大。以长焰煤作为底物构建厌氧发酵系统,通过对生物甲烷产气量、中间关键液相产物、微生物群落结构、产甲烷代谢路径以及发酵前后残煤表面官能团等的测试和分析,探讨了石墨烯对厌氧发酵产生物甲烷的促进效应。结果表明,在以煤为底物的厌氧发酵系统中添加0.4 g/L的石墨烯有效增强了整个厌氧发酵的进行,不仅提高了甲烷产气量,同时也提前了甲烷的产出高峰期。在发酵初期,水解菌群(Paraclostridium)和产氢产乙酸菌群(Alcaligenes、Sphaerochaeta)的活性增强,前期积累了充足的营养物质。在产甲烷高峰期,添加石墨烯后Methanoculleus丰度降低而Methanosarcina丰度显著提高,乙酰辅酶A脱羰基酶/合成酶β亚基和γδ亚基作为乙酸合成途径中的关键酶,分别增加了233.54%和3.32%,这使得Methanosarcina丰度明显上升且主要进行乙酸营养型产甲烷,细菌群落中能够利用乙酸乙醇类物质的Geobacter和Anaerovorax丰度增高,其中丰度升高较明显的Geobacter可能通过与石墨烯辅助的生物电连接与Methanosarcina进行DIET,这种电子传递方式在一定程度上加速了生物甲烷的生成。产气残煤表面的羰基碳(C=O)、羧基碳(COO—)在添加石墨烯后分别下降了42.8%和49.5%,说明石墨烯有效促进了微生物对煤的降解。石墨烯的添加提高了菌群的活性和降解效率,加快了厌氧发酵进程,为产甲烷菌群提供了丰富的底物,提高了甲烷产气量。

导电材料强化厌氧处理技术研究进展

厌氧处理技术是处理有机废物、生产清洁能源的有效技术,而传统厌氧技术存在挥发性脂肪酸(VFA)积累、甲烷产率低、微生物生长速度慢、反应器运行不稳定等问题,使得能源消耗和处理成本不断增加。近年来,碳基导电材料和铁基导电材料因具有比表面积大、导电性能良好、经济环保等优点,被广泛应用于废水厌氧处理领域。导电材料可促进共营养细菌和产甲烷古菌之间的直接种间电子转移(DIET),从而促进污染物高效降解并提升产甲烷效能。在讨论导电材料性质的基础上,从提高COD去除率、促进VFA消耗、促进产甲烷以及改善微生物群落角度,论述了导电材料对厌氧处理技术的强化作用,在厌氧处理过程中添加导电材料可以加速和稳定有机废物向甲烷的转化,并对未来的发展前景提出了一些建议,以期为先进导电材料的开发及其工程应用提供参考。

基于导电材料强化抗生素胁迫厌氧消化的研究进展

厌氧消化是处理含抗生素有机废物的常用技术手段,但高浓度抗生素会抑制厌氧微生物菌群活性,从而干扰厌氧消化效能和抗生素自身降解效率。近年来,导电材料强化含抗生素有机废物厌氧消化取得了良好效果,有机废物资源回收效率得到进一步提升。本文从抗生素使用现状和对厌氧消化代谢过程的影响出发,讨论了抗生素在厌氧消化中的迁移转化机制,重点阐述了铁基和碳基导电材料在抗生素胁迫厌氧消化系统中的应用及生化作用机理。研究表明:通过富集功能性微生物、强化微生物种间电子传递以及削减厌氧消化系统中的抗生素和抗生素抗性基因,导电材料可以提升厌氧消化产甲烷效能、降低抗生素污染的环境风险。最后,从构建生物信息网络、开发优化新型材料和处理多元污染物方面对导电材料强化技术的发展方向进行了展望。

碳材料增强微生物种间电子传递强化餐厨垃圾厌氧消化产甲烷研究综述

餐厨垃圾厌氧消化产甲烷是餐厨垃圾资源化、能源化利用的重要途径,但其有机物互营产甲烷过程易受微生物间接种间电子传递的低速瓶颈和低氢分压限制的影响,导致有机酸累积抑制、甲烷回收效率低,系统稳定性差。近年来大量研究表明,多种导电碳材料可通过介导互营微生物直接种间电子传递(DIET),大幅提高种间电子传递速率,并突破低氢分压限制,强化餐厨垃圾厌氧产甲烷。文章在梳理有机物厌氧消化微生物种间电子传递机理的基础上,总结了活性炭、生物炭、碳布、石墨等多种导电碳材料介导微生物DIET强化餐厨垃圾厌氧消化的最新研究进展,包括碳材料对互营细菌和产甲烷菌种间电子传递、产气滞后期及甲烷产量、有机酸代谢和系统稳定性、厌氧微生物群落结构动态演化的影响。尽管外源碳材料介导DIET强化餐厨垃圾厌氧消化的优异效果已被证实,但碳材料诱导互营微生物间DIET体系建立的机理尚未明确,而且碳材料如何在大型沼气工程中持续稳定发挥功效及其回收利用问题仍未有效解决。在未来的研究中,碳材料诱导下高效DIET功能菌群的构建机制及其工程化应用将是重点研究方向。

电子转移途径中芳香族氨基酸的引入提高了细胞色素P450s的催化性能

细胞色素P450s是用于生物合成的多功能催化剂.在P450催化循环中,需要两个电子来还原血红素铁,并通过电子转移途径(eTPs)激活随后的还原,该步骤是反应的限速步骤.本文重新设计了巨大芽孢杆菌P450 BM3的e TPs,大幅提高了其催化性能.通过在P450 BM3的e TP中引入芳香族氨基酸,“最佳”变体P2H02(A399Y/Q403F)的催化效率比P450 BM3野生型催化效率提高了12.9倍(kcat/KM从65.8 L mol^(-1)s^(-1)提高到913.5 L mol^(-1)s^(-1)).分子动力学模拟和电子传递分析表明,在辅因子FMN和血红素之间引入的芳香族氨基酸可以显著提高电子转移速率和酶催化性能.同时,在电子传递途径中引入酪氨酸可以保护P450的催化中心,使其避免被氧化性中间产物所破坏,从而提高其催化效率.此外,引入芳香族氨基酸的策略被证明对其他P450(如CYP116B3)同样有效,改造后的酶表现出显著提高的催化效率.综上,本文策略有望拓展到其他带有长程电子传递链的氧化还原酶上,成为改造的通用策略.

微电流耦合磁性炭强化有机物厌氧降解研究进展

厌氧生物技术具有应用范围广、能耗低与资源回收等突出优势,是实现废水有机污染物“减污降碳协同增效”最有效的绿色技术之一,广泛应用于废水处理领域。但传统厌氧技术出水可生化性差,系统易酸化。如何提高厌氧生物技术的高效性及系统稳定性已成为国内外的研究热点。通过国内外文献调研,分别介绍了磁性炭、微电流以及微电流耦合炭材料这3种方式用于强化厌氧生物技术的研究进展,分析了磁性炭及微电流强化厌氧生物降解有机物存在的强化机理以及目前该技术的应用进展,讨论了微电流耦合碳材料构建二维、三维生物电化学系统对强化厌氧生物降解有机污染物的促进作用,并提出了厌氧生物技术今后研究需关注的重点,以期为厌氧生物降解有机污染物的未来研究提供参考。

钯掺杂纳米塑料对产甲烷颗粒污泥的影响

金属掺杂纳米塑料已被广泛应用在纳米塑料的环境行为与生物效应研究中,但其中掺杂的金属是否会对其生物效应产生影响尚不清楚。以厌氧颗粒污泥为研究对象,基于乳液聚合的方法合成钯(Pd)掺杂的纳米塑料(Pd-NPs),研究它对污泥厌氧消化系统产甲烷性能、微生物群落分布和污泥胞外聚合物的影响。结果表明,Pd-NPs中的Pd会随时间的推移溶出,并通过提高厌氧消化系统中地杆菌(Geobacter)的相对丰度促进电子传递进而促进污泥厌氧消化系统产甲烷量;傅立叶变换红外光谱和三维荧光光谱结果显示,Pd-NPs能够与厌氧颗粒污泥表面胞外聚合物中蛋白质和腐殖酸类物质发生相互作用,使污泥颗粒更易絮凝。这些结果为评估金属掺杂的纳米塑料对厌氧消化系统的影响提供了一定的数据支撑。

Direct Electron Transfer between Glucose Oxidase and Multi-walled Carbon Nanotubes

The direct electrochemical behavior between the glucose oxidase (GOD) and the multi walled carbon nanotubes (MWNTs) has been studied. Two pairs of cyclic voltammetric peaks corresponding to the two different processes, i.e. mass transport and surface reaction of GOD are observed on this MWNTs. The formal potentials with E o′=-0.45 V and E o′=-0.55 V were obtained respectively. The GOD film was observed on the carbon nanotube by the TEM.

Extending the operational lifetimes of all-direct electron transfer enzymatic biofuel cells by magnetically assembling and exchanging the active biocatalyst layers on stationary electrodes

Enzymatic biofuel cells promise green power generation from a variety of natural resources, yet these systems all suffer from time-dependent degradati on effects, in particular progress! ng inactivation of enzymes, which severely limit the operati on al lifetimes of such power sources. To extend operational lifetimes, we introduce a method to magnetically exchange exhausted enzymes for fresh ones. To this end, anodic and cathodic enzymes or enzyme cascades are immobilized on carbon coated magnetic nanoparticles. Under the action of suitable magnetic field gradie nts, these nano particles are assembled on the respective stati onary electrodes, or released from the electrodes for collection and subsequent excha nge. We dem on strate this method on a fructose/oxygen con suming biofuel cell emplo ying fructose dehydroge nase and bilirubin oxidase as well as on anodic and cathodic cascades employing fructose dehydrogenase/invertase and bilirubin oxidase/catalase, respectively. The en zyme-modified nan oparticles support direct electro n transfer bioelectrocatalytic curre nts by wiring the redox active cofactors to the carbonaceous coating and from there to the electrode surfaces. The facile injection, assembly, and removal of enzyme-modified magnetic nan oparticles along with fuel solutio n provides a promisi ng approach to exte nd the operati on al lifetime of enzymatic biofuel cells without the need for exchanging entire systems including chambers and electrodes.

Different outer membrane c‐type cytochromes are involved in direct interspecies electron transfer to Geobacter or Methanosarcina species

Direct interspecies electron transfer(DIET)may be most important in methanogenic environments,but mechanistic studies of DIET to date have primarily focused on cocultures in which fumarate was the terminal electron acceptor.To better understand DIET with methanogens,the transcriptome of Geobacter metallireducens during DIET‐based growth with G.sulfurreducens reducing fumarate was compared with G.metallireducens grown in coculture with diverse Methanosarcina.The transcriptome of G.metallireducens cocultured with G.sulfurreducens was significantly different from those with Methanosarcina.Furthermore,the transcriptome of G.metallireducens grown with Methanosarcina barkeri,which lacks outer‐surface c‐type cytochromes,differed from those of G.metallireducens cocultured with M.acetivorans or M.subterranea,which have an outer‐surface c‐type cytochrome that serves as an electrical connect for DIET.Differences in G.metallireducens expression patterns for genes involved in extracellular electron transfer were particularly notable.Cocultures with c‐type cytochrome deletion mutant strains,ΔGmet_0930,ΔGmet_0557 andΔGmet_2896,never became established with G.sulfurreducens but adapted to grow with all three Methanosarcina.Two porin–cytochrome complexes,PccF and PccG,were important for DIET;however,PccG was more important for growth with Methanosarcina.Unlike cocultures with G.sulfurreducens and M.acetivorans,electrically conductive pili were not needed for growth with M.barkeri.Shewanella oneidensis,another electroactive microbe with abundant outer‐surface c‐type cytochromes,did not grow via DIET.The results demonstrate that the presence of outer‐surface c‐type cytochromes does not necessarily confer the capacity for DIET and emphasize the impact of the electron‐accepting partner on the physiology of the electron‐donating DIET partner.