Mung bean(Vigna radiata)sprouts are widely consumed worldwide due to their high nutritional value.However,the low yield and microbial contamination of mung bean sprouts seriously reduces their economic value.This stud...Mung bean(Vigna radiata)sprouts are widely consumed worldwide due to their high nutritional value.However,the low yield and microbial contamination of mung bean sprouts seriously reduces their economic value.This study investigates the effects of non-thermal plasma on the quality and microbial reduction of mung bean sprouts by pretreatment of seeds in water for different times(0,1,3 and 6 min).The quality results showed that short-time plasma treatment(1 and 3 min)promoted seed germination and seedling growth,whereas long-time plasma treatment(6 min)had inhibitory effects.Plasma also had a similar dose effects on the total flavonoid and phenolic contents of mung bean sprouts.The microbiological results showed that plasma treatment achieved a reduction of native microorganisms ranging from 0.54 to 7.09 log for fungi and 0.29 to 6.80 log for bacteria at 96 h incubation.Meanwhile,plasma treatment could also efficiently inactivate artificially inoculated Salmonella typhimurium(1.83–6.22 log)and yeast(0.53–3.19 log)on mung bean seeds.The results of seed coat permeability tests and scanning electron microscopy showed that plasma could damage the seed coat structure,consequently increasing the electrical conductivity of mung bean seeds.The physicochemical analysis of plasma-treated water showed that plasma generated various long-and short-lived active species[nitric oxide radicals(NO·),hydroxyl radicals(·OH),singlet oxygen(1O2),hydrogen peroxide(H_(2)O_(2)),nitrate(NO_(3)^(-)),and nitrite(NO_(2)^(-))]in water,thus the oxidizability,acidity and conductivity of plasma-treated water were all increased in a treatment timedependent manner.The result for mimicked chemical mixtures confirmed the synergistic effect of activity of H_(2)O_(2),NO_(3)^(-)and NO_(2)^(-)on bacterial inactivation and plant growth promotion.Taken together,these results imply that plasma pretreatment of mung bean seeds in water with moderate oxidizability and acidity is an effective method to improve the yield of mung bean sprouts and reduce microbial contamination.展开更多
Enantiomerically pure syn-4,5-dihydroxy carboxylic acid lactones were prepared by microbial reduction of acyl lactones with resting cell of Aspergillus niger.
Despite more than a decade of study,there are still significant obstacles to overcome before graphene can be successfully produced on a large scale for commercial use.Chemical oxidation of graphite to produce graphene...Despite more than a decade of study,there are still significant obstacles to overcome before graphene can be successfully produced on a large scale for commercial use.Chemical oxidation of graphite to produce graphene oxide(GO),followed by a subsequent reduction process to synthesize reduced graphene oxide(rGO),is considered the most practical method for mass production.Microorganisms,which are abundant in nature and inexpensive,are one of the potential green reductants for rGO synthesis.However,there is no recent review discussing the reported microbial reduction of GO in detail.To address this,we present a comprehensive review on the reduction of GO by a range of microorganisms and compared their efficacies and reaction conditions.Also,presented were the mechanisms by which microorganisms reduce GO.We also reviewed the recent advancements in using microbially reduced GO as the anode and cathode material in the microbial fuel cell(MFC)and algal biophotovoltaics(BPV),as well as the challenges and future directions in microbial fuel cell research.展开更多
In the system of nitric oxide removal from the flue gas by metal chelate absorption, it is an obstacle that ferrous absorbents are easily oxidized by oxygen in the flue gas to ferric counterparts, which are not capabl...In the system of nitric oxide removal from the flue gas by metal chelate absorption, it is an obstacle that ferrous absorbents are easily oxidized by oxygen in the flue gas to ferric counterparts, which are not capable of binding NO. By adding iron metal or electrochemical method, Fe III (EDTA) can be reduced to Fe II (EDTA). However, there are various drawbacks associated with these techniques. The dissimilatory reduction of Fe III (EDTA) with microorganisms in the system of nitric oxide removal by metal chelate absorption was investigated. Ammonium salt instead of nitrate was used as the nitrogen source, as nitrates inhibited the reduction of Fe III due to the competition between the two electron acceptors. Supplemental glucose and lactate stimulated the formation of Fe II more than ethanol as the carbon sources. The microorganisms cultured at 50℃ were not very sensitive to the other experimental temperature, the reduction percentage of Fe III varied little with the temperature range of 30—50℃. Concentrated Na 2CO 3 solution was added to adjust the solution pH to an optimal pH range of 6—7 The overall results revealed that the dissimilatory ferric reducing microorganisms present in the mix culture are probably neutrophilic, moderately thermophilic Fe III reducers.展开更多
Process control parameters influencing microbial perchlorate reduction via a flow-through zero-valent iron （ZVI） column reactor were investigated in order to optimize perchlorate removal from water. Mixed perchlorat...Process control parameters influencing microbial perchlorate reduction via a flow-through zero-valent iron （ZVI） column reactor were investigated in order to optimize perchlorate removal from water. Mixed perchlorate reducers were obtained from a wastewater treatment plant and inoculated into the reactor without further acclimation. Examined parameters included hydraulic residence time （HRT）, pH, nutrients requirement, and perchlorate reduction kinetics. The minimum HRT for the system was concluded to be 8 hr. The removal efficiency of 10 mg. L-1 influent perchlorate concentration was reduced by 20%-80% without control to the neutral pH （HRT = 8 hr）. Therefore pH was determined to be an important parameter for microbial perchlorate reduction. Furthermore, a viable alternative to pH buffer was discussed. The microbial perchlorate reduction followed the first order kinetics, with a rate constant （K） of 0.761 hr-1. The results from this study will contribute to the implementation of a safe, cost effective, and efficient system for perchlorate reduction to below regulated levels.展开更多
In soil-rice systems,microbial reduction of iron(Fe)has been recognized as a crucial biogeochemical process that regulates Fe and chromium(Cr)translocation;however,the underlying processes are unknown.To investigate t...In soil-rice systems,microbial reduction of iron(Fe)has been recognized as a crucial biogeochemical process that regulates Fe and chromium(Cr)translocation;however,the underlying processes are unknown.To investigate the impacts of biochar on the biochemical cycling of Fe and Cr and their toxicity to rice,maize straw biochar was applied at 1%(weight/weight)to a paddy soil spiked with 300 mg kg^(-1)Cr under two phosphorus(P)levels(0 or 90 mg kg^(-1))in a pot experiment.The key microbial groups affecting Fe dissimilatory reduction and their environmental drivers were explored.Biochar inhibited root Cr uptake by 36%,owing to the promoted iron plaque(IP)formation on the rice root surface.Correlation analysis showed that Fe concentration in pore water was strongly linked to the abundances of Geobacter(r=0.81-0.94,P<0.05)and Clostridium(r=0.83-0.95,P<0.05),indicating that Geobacter and Clostridium played essential roles in Fe reduction.Redundancy analysis showed that labile carbon and pore water P concentrations were the key determinants influencing Fe-reducing bacterial abundances,accounting for 42%and 32%of the variation in community composition,respectively.Besides,biochar increased Fe and P concentrations in root cell walls,which retained more Cr.Overall,Cr stress in rice under biochar treatment was relieved through increasing IP formation and altering subcellular distribution.These mechanistic insights had important implications for reducing Cr uptake by rice.展开更多
In this study, Pb(Ⅱ) was used as a target heavy metal pollutant, and the metabolism of Shewanella putrefaciens(S. putrefaciens) was applied to achieve reducing conditions to study the effect of microbial reduction on...In this study, Pb(Ⅱ) was used as a target heavy metal pollutant, and the metabolism of Shewanella putrefaciens(S. putrefaciens) was applied to achieve reducing conditions to study the effect of microbial reduction on lead that was preadsorbed on graphene oxide(GO) surfaces.The results showed that GO was transformed to its reduced form(r-GO) by bacteria, and this process induced the release of Pb(Ⅱ) adsorbed on the GO surfaces. After 72 hr of exposure in an S. putrefaciens system, 5.76% of the total adsorbed Pb(Ⅱ) was stably dispersed in solution in the form of a Pb(Ⅱ)-extracellular polymer substance(EPS) complex, while another portion of Pb(Ⅱ) released from GO-Pb(Ⅱ) was observed as lead phosphate hydroxide(Pb_(10)(PO_(4))_(6)(OH)_(2))precipitates or adsorbed species on the surface of the cell. Additionally, increasing pH induced the stripping of oxidative debris(OD) and elevated the content of dispersible Pb(Ⅱ)in aqueous solution under the conditions of S. putrefaciens metabolism. These research results provide valuable information regarding the migration of heavy metals adsorbed on GO under reducing conditions due to microbial metabolism.展开更多
We investigated the reduction of lepidocrocite(γ-FeOOH) by Shewanella oneidensis MR-1 in the presence and absence of Cd. The results showed that Cd^(2+) retarded microbial reduction of γ-Fe OOH and avoided formation...We investigated the reduction of lepidocrocite(γ-FeOOH) by Shewanella oneidensis MR-1 in the presence and absence of Cd. The results showed that Cd^(2+) retarded microbial reduction of γ-Fe OOH and avoided formation of magnetite. The inhibitory effect on γ-Fe OOH transformation may not result from Cd^(2+) toxicity to the bacterium; it rather was probably due to competitive adsorption between Cd^(2+) and Fe^(2+) on γ-Fe OOH as its surface reduction catalyzed by adsorbed Fe^(2+) was eliminated by adsorption of Cd^(2+).展开更多
Fe reducing bacteria(FRB),through extracellular electron transfer(EET)pathway,can reduce Fe(III)nanoparticles,thereby affecting the migration,transformation,and degradation of pollutants.However,the interaction of Fe(...Fe reducing bacteria(FRB),through extracellular electron transfer(EET)pathway,can reduce Fe(III)nanoparticles,thereby affecting the migration,transformation,and degradation of pollutants.However,the interaction of Fe(III)nanoparticles with the most commonly identified FRB,Geobacter sulfurreducens PCA,remains poorly understood.Herein,we demonstrated that the synergistic role of outer membrane proteins and periplasmic proteins in the EET process for-Fe_(2)O_(3),Fe3O4,and𝛽α-FeOOH nanoparticles by construction of multiple gene knockout strain.oxpG(involved in the type II secretion system)and omcST(outer membrane c-type cytochrome)medi-ated pathways accounted for approximately 67%of the total reduction of𝛼α-Fe_(2)O_(3) nanoparticles.The residual reduction of𝛼α-Fe_(2)O_(3) nanoparticles in∆oxpG-omcST strain was likely caused by redox-active substances in cell supernatant.Conversely,the reduction of dissolved Fe(III)was almost unaffected in∆oxpG-omcST strain at the same concentration.However,at high dissolved Fe(III)concentration,the reduction significantly decreased due to the formation of Fe(III)nanoparticles,suggesting that this EET process is specific to Fe(III)nanoparticles.Overall,our study provided a more comprehensive understanding for the EET pathways between G.sulfurreducens PCA and different Fe(III)species,enriching our knowledge on the role of microorganisms in iron biogeochemical cycles and remediation strategies of pollutants.展开更多
The origin of sedimentary dolomite has become a long-standing problem in the Earth Sciences.Some carbonate minerals like ankerite have the same crystal structure as dolomite,hence their genesis may provide clues to he...The origin of sedimentary dolomite has become a long-standing problem in the Earth Sciences.Some carbonate minerals like ankerite have the same crystal structure as dolomite,hence their genesis may provide clues to help solving the dolomite problem.The purpose of this study was to probe whether microbial activity can be involved in the formation of ankerite.Bio-carbonation experiments associated with microbial iron reduction were performed in batch systems with various concentrations of Ca^(2+)(0–20 mmol/L),with a marine iron-reducing bacterium Shewanella piezotolerans WP3 as the reaction mediator,and with lactate and ferrihydrite as the respective electron donor and acceptor.Our biomineralization data showed that Ca-amendments expedited microbially-mediated ferrihydrite reduction by enhancing the adhesion between WP3 cells and ferrihydrite particles.After bioreduction,siderite occurred as the principal secondary mineral in the Ca-free systems.Instead,Ca-Fe carbonates were formed when Ca^(2+)ions were present.The CaCO_(3) content of microbially-induced Ca-Fe carbonates was positively correlated with the initial Ca2+concentration.The Ca-Fe carbonate phase produced in the 20 mmol/L Ca-amended biosystems had a chemical formula of Ca_(0.8)Fe_(1.2)(CO_(3))_(2),which is close to the theoretical composition of ankerite.This ankeritelike phase was nanometric in size and spherical,Ca-Fe disordered,and structurally defective.Our simulated diagenesis experiments further demonstrated that the resulting ankerite-like phase could be converted into ordered ankerite under hydrothermal conditions.We introduced the term“proto-ankerite”to define the Ca-Fe phases that possess near-ankerite stoichiometry but disordered cation arrangement.On the basis of the present study,we proposed herein that microbial activity is an important contributor to the genesis of sedimentary ankerite by providing the metastable Ca-Fe carbonate precursors.展开更多
As a case study, refined iron（Fe） speciation and quantitative characterization of the reductive reactivity of Fe（Ⅲ）oxides are combined to investigate Fe diagenetic processes in a core sediment from the eutrophic ...As a case study, refined iron（Fe） speciation and quantitative characterization of the reductive reactivity of Fe（Ⅲ）oxides are combined to investigate Fe diagenetic processes in a core sediment from the eutrophic Jiaozhou Bay.The results show that a combination of the two methods can trace Fe transformation in more detail and offer nuanced information on Fe diagenesis from multiple perspectives. This methodology may be used to enhance our understanding of the complex biogeochemical cycling of Fe and sulfur in other studies. Microbial iron reduction（MIR） plays an important role in Fe（Ⅲ） reduction over the upper sediments, while a chemical reduction by reaction with dissolved sulfide is the main process at a deeper（〉 12 cm） layer. The most bioavailable amorphous Fe（Ⅲ） oxides [Fe（Ⅲ）am] are the main source of the MIR, followed by poorly crystalline Fe（Ⅲ） oxides [Fe（Ⅲ）pc）]and magnetite. Well crystalline Fe（Ⅲ） oxides [Fe（Ⅲ）wc] have barely participated in Fe diagenesis. The importance of the MIR over the upper layer may be a combined result of the high availability of highly reactive Fe oxides and low availability of labile organic matter, and the latter is also the ultimate factor limiting sulfate reduction and sulfide accumulation in the sediments. Microbially reducible Fe（Ⅲ） [MR-Fe（Ⅲ）], which is quantified by kinetics of Fe（II）-oxide reduction, mainly consists of the most reactive Fe（Ⅲ）am and less reactive Fe（Ⅲ）pc. The bulk reactivity of the MR-Fe（Ⅲ） pool is equivalent to aged ferrihydrite, and shows down-core decrease due to preferential reduction of highly reactive phases of Fe oxides.展开更多
Microbial Fe(Ⅲ)reduction is a significant driving force for the biogeochemical cycles of C,O,P,S,N,and dominates the natural bio-purification of contaminants in groundwater(e.g.,petroleum hydrocarbons,chlorinated eth...Microbial Fe(Ⅲ)reduction is a significant driving force for the biogeochemical cycles of C,O,P,S,N,and dominates the natural bio-purification of contaminants in groundwater(e.g.,petroleum hydrocarbons,chlorinated ethane,and chromium).In this review,the mechanisms and environmental significance of Fe(Ⅲ)(hydro)oxides bioreduction are summarized.Compared with crystalline Fe(Ⅲ)(hydro)oxides,amorphous Fe(m)(hydro)oxides are more bioavailable.Ligand and electron shuttle both play an important role in microbial Fe(Ⅲ)reduction.The restrictive factors of Fe(Ⅲ)(hydro)oxides bioreduction should be further investigated to reveal the characteristics and mechanisms of the process.It will improve the bioavailability of crystalline Fe(Ⅲ)(hydro)oxides and accelerate the anaerobic oxidation efficiency of the reduction state pollutants.Furthermore,the approach to extract,culture,and incubate the functional Fe(Ⅲ)reducing bacteria from actual complicated environment,and applying it to the bioremediation of organic,ammonia,and heavy metals contaminated groundwater will become a research topic in the future.There are a broad application prospects of Fe(Ⅲ)(hydro)oxides bioreduction to groundwater bioremediation,which includes the in situ injection and permeable reactive barriers and the innovative Kariz wells system.The study provides an important reference for the treatment of reduced pollutants in contaminated groundwater.展开更多
Due to the toxicity of bioaccumulative organohalides to human beings and ecosystems,a variety of biotic and abiotic remediation methods have been developed to remove organohalides from contaminated environments.Biorem...Due to the toxicity of bioaccumulative organohalides to human beings and ecosystems,a variety of biotic and abiotic remediation methods have been developed to remove organohalides from contaminated environments.Bioremediation employing organohalide-respiring bacteria(OHRB)-mediated microbial reductive dehalogenation(Bio-RD)represents a cost-effective and environmentally friendly approach to attenuate highly-halogenated organohalides,specifically organohalides in soil,sediment and other anoxic environments.Nonetheless,many factors severely restrict the implications of OHRB-based bioremediation,including incomplete dehalogenation,low abundance of OHRB and consequent low dechlorination activity.Recently,the development of in situ chemical oxidation(ISCO)based on sulfate radicals(SO_(4)^(·−))via the persulfate activation and oxidation(PAO)process has attracted tremendous research interest for the remediation of lowly-halogenated organohalides due to its following advantages,e.g.,complete attenuation,high reactivity and no selectivity to organohalides.Therefore,integration of OHRB-mediated Bio-RD and subsequent PAO(Bio-RD-PAO)may provide a promising solution to the remediation of organohalides.In this review,we first provide an overview of current progress in Bio-RD and PAO and compare their limitations and advantages.We then critically discuss the integration of Bio-RD and PAO(Bio-RD-PAO)for complete attenuation of organohalides and its prospects for future remediation applications.Overall,Bio-RD-PAO opens up opportunities for complete attenuation and consequent effective in situ remediation of persistent organohalide pollution.展开更多
The toxic and recalcitrant polychlorinated biphenyls （PCBs） adversely affect human and biota by bioaccumulation and biomagnification through food chain. In this study, an anaerobic microcosm was developed to extensi...The toxic and recalcitrant polychlorinated biphenyls （PCBs） adversely affect human and biota by bioaccumulation and biomagnification through food chain. In this study, an anaerobic microcosm was developed to extensively dechlorinate hexa- and hepta-CBs in Aroclor 1260. After 4 months of incubation in defined mineral salts medium amended PCBs （70μmol· L^-1） and lactate （10 mmol· L^-1）, the culture dechlorinated hexa-CBs from 40.2% to 8.7% and hepta-CBs 33.6% to 11.6%, with dechlorination efficiencies of 78.3% and 65.5%, respectively （all in moL ratio）. This dechlorination process led to tetra-CBs （46.4%） as the predominant dechlorination products, followed by penta- （22.1%） and tri-CBs （5.4%）. The number of meta chlorines per biphenyl decreased from 2.50 to 1.41. Results of quantitative real-time PCR show that Dehalococcoides cells increased from 2.39 × 10^5±0.5× 10^5 to 4.99 ×10^7±0.32 ×10^7 copies mL^-1 after 120 days of incubation, suggesting that Dehalococcoides play a major role in reductive dechlorination of PCBs. This study could prove the feasibility of anaerobic reductive culture enrichment for the dehalogenation of highly chlorinated PCBs, which is priorto be applied for in situ biorernediation of notorious halogenated compounds.展开更多
基金supported by National Natural Science Foundation of China(Nos.11605159 and 11405147)Chinese Postdoctoral Science Foundation(No.2017M612412)+3 种基金the Foundation of Key Technology Research Project of Henan Province(No.182102311115)Key Discipline Construction Project of Zhengzhou University(No.32410257)Youth Innovation Project of Key Discipline of Zhengzhou University(No.XKZDQN202002)Natural Science Foundation of Henan Province(No.202300410013)。
文摘Mung bean(Vigna radiata)sprouts are widely consumed worldwide due to their high nutritional value.However,the low yield and microbial contamination of mung bean sprouts seriously reduces their economic value.This study investigates the effects of non-thermal plasma on the quality and microbial reduction of mung bean sprouts by pretreatment of seeds in water for different times(0,1,3 and 6 min).The quality results showed that short-time plasma treatment(1 and 3 min)promoted seed germination and seedling growth,whereas long-time plasma treatment(6 min)had inhibitory effects.Plasma also had a similar dose effects on the total flavonoid and phenolic contents of mung bean sprouts.The microbiological results showed that plasma treatment achieved a reduction of native microorganisms ranging from 0.54 to 7.09 log for fungi and 0.29 to 6.80 log for bacteria at 96 h incubation.Meanwhile,plasma treatment could also efficiently inactivate artificially inoculated Salmonella typhimurium(1.83–6.22 log)and yeast(0.53–3.19 log)on mung bean seeds.The results of seed coat permeability tests and scanning electron microscopy showed that plasma could damage the seed coat structure,consequently increasing the electrical conductivity of mung bean seeds.The physicochemical analysis of plasma-treated water showed that plasma generated various long-and short-lived active species[nitric oxide radicals(NO·),hydroxyl radicals(·OH),singlet oxygen(1O2),hydrogen peroxide(H_(2)O_(2)),nitrate(NO_(3)^(-)),and nitrite(NO_(2)^(-))]in water,thus the oxidizability,acidity and conductivity of plasma-treated water were all increased in a treatment timedependent manner.The result for mimicked chemical mixtures confirmed the synergistic effect of activity of H_(2)O_(2),NO_(3)^(-)and NO_(2)^(-)on bacterial inactivation and plant growth promotion.Taken together,these results imply that plasma pretreatment of mung bean seeds in water with moderate oxidizability and acidity is an effective method to improve the yield of mung bean sprouts and reduce microbial contamination.
文摘Enantiomerically pure syn-4,5-dihydroxy carboxylic acid lactones were prepared by microbial reduction of acyl lactones with resting cell of Aspergillus niger.
基金This work was supported by the Ministry of Higher Education Malaysia via Fundamental Research Grant Scheme(FRGS)[FRGS/1/2022/STG01/UM/03/2][FP064-2022]Ministry of Higher Education Malaysia under the Higher Institution Centre of Excellence(HICoE)Programme[IOES-2014F]+1 种基金UM Innovate Fund[PPSI-2020-HICOE-03]the Research University Grant,Universiti Malaya[RU003-2022].
文摘Despite more than a decade of study,there are still significant obstacles to overcome before graphene can be successfully produced on a large scale for commercial use.Chemical oxidation of graphite to produce graphene oxide(GO),followed by a subsequent reduction process to synthesize reduced graphene oxide(rGO),is considered the most practical method for mass production.Microorganisms,which are abundant in nature and inexpensive,are one of the potential green reductants for rGO synthesis.However,there is no recent review discussing the reported microbial reduction of GO in detail.To address this,we present a comprehensive review on the reduction of GO by a range of microorganisms and compared their efficacies and reaction conditions.Also,presented were the mechanisms by which microorganisms reduce GO.We also reviewed the recent advancements in using microbially reduced GO as the anode and cathode material in the microbial fuel cell(MFC)and algal biophotovoltaics(BPV),as well as the challenges and future directions in microbial fuel cell research.
文摘In the system of nitric oxide removal from the flue gas by metal chelate absorption, it is an obstacle that ferrous absorbents are easily oxidized by oxygen in the flue gas to ferric counterparts, which are not capable of binding NO. By adding iron metal or electrochemical method, Fe III (EDTA) can be reduced to Fe II (EDTA). However, there are various drawbacks associated with these techniques. The dissimilatory reduction of Fe III (EDTA) with microorganisms in the system of nitric oxide removal by metal chelate absorption was investigated. Ammonium salt instead of nitrate was used as the nitrogen source, as nitrates inhibited the reduction of Fe III due to the competition between the two electron acceptors. Supplemental glucose and lactate stimulated the formation of Fe II more than ethanol as the carbon sources. The microorganisms cultured at 50℃ were not very sensitive to the other experimental temperature, the reduction percentage of Fe III varied little with the temperature range of 30—50℃. Concentrated Na 2CO 3 solution was added to adjust the solution pH to an optimal pH range of 6—7 The overall results revealed that the dissimilatory ferric reducing microorganisms present in the mix culture are probably neutrophilic, moderately thermophilic Fe III reducers.
文摘Process control parameters influencing microbial perchlorate reduction via a flow-through zero-valent iron （ZVI） column reactor were investigated in order to optimize perchlorate removal from water. Mixed perchlorate reducers were obtained from a wastewater treatment plant and inoculated into the reactor without further acclimation. Examined parameters included hydraulic residence time （HRT）, pH, nutrients requirement, and perchlorate reduction kinetics. The minimum HRT for the system was concluded to be 8 hr. The removal efficiency of 10 mg. L-1 influent perchlorate concentration was reduced by 20%-80% without control to the neutral pH （HRT = 8 hr）. Therefore pH was determined to be an important parameter for microbial perchlorate reduction. Furthermore, a viable alternative to pH buffer was discussed. The microbial perchlorate reduction followed the first order kinetics, with a rate constant （K） of 0.761 hr-1. The results from this study will contribute to the implementation of a safe, cost effective, and efficient system for perchlorate reduction to below regulated levels.
基金supported by the National Natural Science Foundation of China(Nos.42107017 and 32172121)。
文摘In soil-rice systems,microbial reduction of iron(Fe)has been recognized as a crucial biogeochemical process that regulates Fe and chromium(Cr)translocation;however,the underlying processes are unknown.To investigate the impacts of biochar on the biochemical cycling of Fe and Cr and their toxicity to rice,maize straw biochar was applied at 1%(weight/weight)to a paddy soil spiked with 300 mg kg^(-1)Cr under two phosphorus(P)levels(0 or 90 mg kg^(-1))in a pot experiment.The key microbial groups affecting Fe dissimilatory reduction and their environmental drivers were explored.Biochar inhibited root Cr uptake by 36%,owing to the promoted iron plaque(IP)formation on the rice root surface.Correlation analysis showed that Fe concentration in pore water was strongly linked to the abundances of Geobacter(r=0.81-0.94,P<0.05)and Clostridium(r=0.83-0.95,P<0.05),indicating that Geobacter and Clostridium played essential roles in Fe reduction.Redundancy analysis showed that labile carbon and pore water P concentrations were the key determinants influencing Fe-reducing bacterial abundances,accounting for 42%and 32%of the variation in community composition,respectively.Besides,biochar increased Fe and P concentrations in root cell walls,which retained more Cr.Overall,Cr stress in rice under biochar treatment was relieved through increasing IP formation and altering subcellular distribution.These mechanistic insights had important implications for reducing Cr uptake by rice.
基金supported by the National Key Project of Research and Development Plan of China (No. 2017YFC04034033)the Shanxi National Science Foundation (No. 2020JQ-664)the Key Laboratory of Education Department of Shanxi Province, China (No. 20JS085)。
文摘In this study, Pb(Ⅱ) was used as a target heavy metal pollutant, and the metabolism of Shewanella putrefaciens(S. putrefaciens) was applied to achieve reducing conditions to study the effect of microbial reduction on lead that was preadsorbed on graphene oxide(GO) surfaces.The results showed that GO was transformed to its reduced form(r-GO) by bacteria, and this process induced the release of Pb(Ⅱ) adsorbed on the GO surfaces. After 72 hr of exposure in an S. putrefaciens system, 5.76% of the total adsorbed Pb(Ⅱ) was stably dispersed in solution in the form of a Pb(Ⅱ)-extracellular polymer substance(EPS) complex, while another portion of Pb(Ⅱ) released from GO-Pb(Ⅱ) was observed as lead phosphate hydroxide(Pb_(10)(PO_(4))_(6)(OH)_(2))precipitates or adsorbed species on the surface of the cell. Additionally, increasing pH induced the stripping of oxidative debris(OD) and elevated the content of dispersible Pb(Ⅱ)in aqueous solution under the conditions of S. putrefaciens metabolism. These research results provide valuable information regarding the migration of heavy metals adsorbed on GO under reducing conditions due to microbial metabolism.
基金financially supported by the National Natural Science Foundation of China(41601239)the Highlevel Leading Talent Introduction Program of GDAS,the China Postdoctoral Science Foundation(2016M600644)the"Pearl River Talents"Postdoctoral Program of Guangdong Province,and the National Key Research and Development Program of China(2016YFD0800703)
文摘We investigated the reduction of lepidocrocite(γ-FeOOH) by Shewanella oneidensis MR-1 in the presence and absence of Cd. The results showed that Cd^(2+) retarded microbial reduction of γ-Fe OOH and avoided formation of magnetite. The inhibitory effect on γ-Fe OOH transformation may not result from Cd^(2+) toxicity to the bacterium; it rather was probably due to competitive adsorption between Cd^(2+) and Fe^(2+) on γ-Fe OOH as its surface reduction catalyzed by adsorbed Fe^(2+) was eliminated by adsorption of Cd^(2+).
基金supported by the National Key Research and Development Project(No.2020YFA0907500)the National Natural Science Foundation of China(No.22476206)+1 种基金the supports from the National Young Top-Notch Talents(No.W03070030)Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.Y202011).
文摘Fe reducing bacteria(FRB),through extracellular electron transfer(EET)pathway,can reduce Fe(III)nanoparticles,thereby affecting the migration,transformation,and degradation of pollutants.However,the interaction of Fe(III)nanoparticles with the most commonly identified FRB,Geobacter sulfurreducens PCA,remains poorly understood.Herein,we demonstrated that the synergistic role of outer membrane proteins and periplasmic proteins in the EET process for-Fe_(2)O_(3),Fe3O4,and𝛽α-FeOOH nanoparticles by construction of multiple gene knockout strain.oxpG(involved in the type II secretion system)and omcST(outer membrane c-type cytochrome)medi-ated pathways accounted for approximately 67%of the total reduction of𝛼α-Fe_(2)O_(3) nanoparticles.The residual reduction of𝛼α-Fe_(2)O_(3) nanoparticles in∆oxpG-omcST strain was likely caused by redox-active substances in cell supernatant.Conversely,the reduction of dissolved Fe(III)was almost unaffected in∆oxpG-omcST strain at the same concentration.However,at high dissolved Fe(III)concentration,the reduction significantly decreased due to the formation of Fe(III)nanoparticles,suggesting that this EET process is specific to Fe(III)nanoparticles.Overall,our study provided a more comprehensive understanding for the EET pathways between G.sulfurreducens PCA and different Fe(III)species,enriching our knowledge on the role of microorganisms in iron biogeochemical cycles and remediation strategies of pollutants.
基金This research was jointly supported by the National Natural Science Foundation of China(Grant Nos.42272046,42293292 and 42072336)the National Key R&D Program of China(Grant No.2022YFF0800304)the 111 Project(Grant No.BP0820004).
文摘The origin of sedimentary dolomite has become a long-standing problem in the Earth Sciences.Some carbonate minerals like ankerite have the same crystal structure as dolomite,hence their genesis may provide clues to help solving the dolomite problem.The purpose of this study was to probe whether microbial activity can be involved in the formation of ankerite.Bio-carbonation experiments associated with microbial iron reduction were performed in batch systems with various concentrations of Ca^(2+)(0–20 mmol/L),with a marine iron-reducing bacterium Shewanella piezotolerans WP3 as the reaction mediator,and with lactate and ferrihydrite as the respective electron donor and acceptor.Our biomineralization data showed that Ca-amendments expedited microbially-mediated ferrihydrite reduction by enhancing the adhesion between WP3 cells and ferrihydrite particles.After bioreduction,siderite occurred as the principal secondary mineral in the Ca-free systems.Instead,Ca-Fe carbonates were formed when Ca^(2+)ions were present.The CaCO_(3) content of microbially-induced Ca-Fe carbonates was positively correlated with the initial Ca2+concentration.The Ca-Fe carbonate phase produced in the 20 mmol/L Ca-amended biosystems had a chemical formula of Ca_(0.8)Fe_(1.2)(CO_(3))_(2),which is close to the theoretical composition of ankerite.This ankeritelike phase was nanometric in size and spherical,Ca-Fe disordered,and structurally defective.Our simulated diagenesis experiments further demonstrated that the resulting ankerite-like phase could be converted into ordered ankerite under hydrothermal conditions.We introduced the term“proto-ankerite”to define the Ca-Fe phases that possess near-ankerite stoichiometry but disordered cation arrangement.On the basis of the present study,we proposed herein that microbial activity is an important contributor to the genesis of sedimentary ankerite by providing the metastable Ca-Fe carbonate precursors.
基金The National Natural Science Foundation of China under contract Nos 41576078 and 41276069the Shandong Province Natural Science Foundation of China under contract No.ZR2015DM006the National Key Research and Development Program of China under contract No.2016YFA0601301
文摘As a case study, refined iron（Fe） speciation and quantitative characterization of the reductive reactivity of Fe（Ⅲ）oxides are combined to investigate Fe diagenetic processes in a core sediment from the eutrophic Jiaozhou Bay.The results show that a combination of the two methods can trace Fe transformation in more detail and offer nuanced information on Fe diagenesis from multiple perspectives. This methodology may be used to enhance our understanding of the complex biogeochemical cycling of Fe and sulfur in other studies. Microbial iron reduction（MIR） plays an important role in Fe（Ⅲ） reduction over the upper sediments, while a chemical reduction by reaction with dissolved sulfide is the main process at a deeper（〉 12 cm） layer. The most bioavailable amorphous Fe（Ⅲ） oxides [Fe（Ⅲ）am] are the main source of the MIR, followed by poorly crystalline Fe（Ⅲ） oxides [Fe（Ⅲ）pc）]and magnetite. Well crystalline Fe（Ⅲ） oxides [Fe（Ⅲ）wc] have barely participated in Fe diagenesis. The importance of the MIR over the upper layer may be a combined result of the high availability of highly reactive Fe oxides and low availability of labile organic matter, and the latter is also the ultimate factor limiting sulfate reduction and sulfide accumulation in the sediments. Microbially reducible Fe（Ⅲ） [MR-Fe（Ⅲ）], which is quantified by kinetics of Fe（II）-oxide reduction, mainly consists of the most reactive Fe（Ⅲ）am and less reactive Fe（Ⅲ）pc. The bulk reactivity of the MR-Fe（Ⅲ） pool is equivalent to aged ferrihydrite, and shows down-core decrease due to preferential reduction of highly reactive phases of Fe oxides.
基金This work was supported by the National Natural Science Foundation of China(Grant No.21606214)the Water Pollution Control and Control of Major National Science and Technology Projects in China(No.2018ZX07109-003)。
文摘Microbial Fe(Ⅲ)reduction is a significant driving force for the biogeochemical cycles of C,O,P,S,N,and dominates the natural bio-purification of contaminants in groundwater(e.g.,petroleum hydrocarbons,chlorinated ethane,and chromium).In this review,the mechanisms and environmental significance of Fe(Ⅲ)(hydro)oxides bioreduction are summarized.Compared with crystalline Fe(Ⅲ)(hydro)oxides,amorphous Fe(m)(hydro)oxides are more bioavailable.Ligand and electron shuttle both play an important role in microbial Fe(Ⅲ)reduction.The restrictive factors of Fe(Ⅲ)(hydro)oxides bioreduction should be further investigated to reveal the characteristics and mechanisms of the process.It will improve the bioavailability of crystalline Fe(Ⅲ)(hydro)oxides and accelerate the anaerobic oxidation efficiency of the reduction state pollutants.Furthermore,the approach to extract,culture,and incubate the functional Fe(Ⅲ)reducing bacteria from actual complicated environment,and applying it to the bioremediation of organic,ammonia,and heavy metals contaminated groundwater will become a research topic in the future.There are a broad application prospects of Fe(Ⅲ)(hydro)oxides bioreduction to groundwater bioremediation,which includes the in situ injection and permeable reactive barriers and the innovative Kariz wells system.The study provides an important reference for the treatment of reduced pollutants in contaminated groundwater.
基金This study was supported by the National Natural Science Foundation of China(Grant Nos.41922049 and 41877111)the Fundamental Research Funds for the Central Universities(No.19lgzd30)the Guangzhou Science and Technology Program general project(No.201804010141).
文摘Due to the toxicity of bioaccumulative organohalides to human beings and ecosystems,a variety of biotic and abiotic remediation methods have been developed to remove organohalides from contaminated environments.Bioremediation employing organohalide-respiring bacteria(OHRB)-mediated microbial reductive dehalogenation(Bio-RD)represents a cost-effective and environmentally friendly approach to attenuate highly-halogenated organohalides,specifically organohalides in soil,sediment and other anoxic environments.Nonetheless,many factors severely restrict the implications of OHRB-based bioremediation,including incomplete dehalogenation,low abundance of OHRB and consequent low dechlorination activity.Recently,the development of in situ chemical oxidation(ISCO)based on sulfate radicals(SO_(4)^(·−))via the persulfate activation and oxidation(PAO)process has attracted tremendous research interest for the remediation of lowly-halogenated organohalides due to its following advantages,e.g.,complete attenuation,high reactivity and no selectivity to organohalides.Therefore,integration of OHRB-mediated Bio-RD and subsequent PAO(Bio-RD-PAO)may provide a promising solution to the remediation of organohalides.In this review,we first provide an overview of current progress in Bio-RD and PAO and compare their limitations and advantages.We then critically discuss the integration of Bio-RD and PAO(Bio-RD-PAO)for complete attenuation of organohalides and its prospects for future remediation applications.Overall,Bio-RD-PAO opens up opportunities for complete attenuation and consequent effective in situ remediation of persistent organohalide pollution.
基金Acknowledgements This work was financial supported by grants from the National Natural Science Foundation of China （Grant Nos. 51108014 and 41671310）.
文摘The toxic and recalcitrant polychlorinated biphenyls （PCBs） adversely affect human and biota by bioaccumulation and biomagnification through food chain. In this study, an anaerobic microcosm was developed to extensively dechlorinate hexa- and hepta-CBs in Aroclor 1260. After 4 months of incubation in defined mineral salts medium amended PCBs （70μmol· L^-1） and lactate （10 mmol· L^-1）, the culture dechlorinated hexa-CBs from 40.2% to 8.7% and hepta-CBs 33.6% to 11.6%, with dechlorination efficiencies of 78.3% and 65.5%, respectively （all in moL ratio）. This dechlorination process led to tetra-CBs （46.4%） as the predominant dechlorination products, followed by penta- （22.1%） and tri-CBs （5.4%）. The number of meta chlorines per biphenyl decreased from 2.50 to 1.41. Results of quantitative real-time PCR show that Dehalococcoides cells increased from 2.39 × 10^5±0.5× 10^5 to 4.99 ×10^7±0.32 ×10^7 copies mL^-1 after 120 days of incubation, suggesting that Dehalococcoides play a major role in reductive dechlorination of PCBs. This study could prove the feasibility of anaerobic reductive culture enrichment for the dehalogenation of highly chlorinated PCBs, which is priorto be applied for in situ biorernediation of notorious halogenated compounds.
