微生物燃料电池在环境污染治理研究中的应用进展

近年来,微生物燃料电池(Microbial fuel cells,MFCs)研究得到了迅速发展。由于可以将可生物降解有机物的化学能直接转化为电能,MFCs在环境污染治理及生物产电方面具有良好的应用前景。本文将全面介绍和总结MFCs在环境污染治理中的研究及应用,其中包括脱氮、脱硫、有机污染物降解、重金属污染治理以及垃圾渗滤液处理等方面。此外,本文还提出MFCs在研究及应用过程中存在的主要问题,并对其研究前景进行展望。     

光合细菌在微生物燃料电池中的应用研究进展

微生物燃料电池(Microbial fuel cells,MFCs)降解污染物的同时产生电能,受到广泛关注。光合细菌在MFCs领域的应用实现了污水处理、CO2捕捉、光电转换等多重功能,并显示出了良好的产电特性。本文根据光合细菌在MFCs中所起作用的不同对其产电机理进行评述,并在此基础上分析了光照对光合细菌型MFCs产电性能的影响;针对当前研究的不足与面临的问题,提出了今后光合细菌在MFCs领域的应用前景与发展方向。     

环境中污染物降解基因的水平转移(HGT)及其在生物修复中的作用

水平基因转移是不同于垂直基因转移的遗传物质的交流方式.在污染环境这一特异生态环境中,降解基因的水平转移有着独特的功能与作用.研究环境中污染物降解基因在微生物间的水平转移,更深入地了解微生物种群适应污染环境的机理,对于评价污染物的环境毒理、生物可降解性以及污染环境的可修复潜力具有重要参考价值.在污染物生物修复实践中,可以通过调控降解基因的水平转移,增强污染环境中微生物的降解能力,更有效地发挥生物修复作用.文章将对环境中细菌间基因交流的机制,污染物降解基因的水平转移对微生物适应污染环境的机理、水平基因转移对代谢途径的进化及其对污染物生物修复作用的影响等方面的研究进展做一综述.     

微生物强化修复石油污染土壤的研究进展

微生物修复被认为是去除石油污染物和修复石油污染土壤的一种经济、高效且无二次污染的绿色清洁技术。受土壤环境条件和石油污染物性质等因素制约,土壤中土著石油降解微生物常存在数量不足、活性偏低、生长缓慢等问题,导致修复效果不佳、修复周期偏长。微生物强化修复技术可有效提高微生物降解效能,通过投加具有降解效能的功能菌株或菌剂、营养物质、表面活性剂、生长基质及固定化微生物等手段,可改善提升土著微生物对石油污染土壤的修复效果。文中梳理了已报道的石油降解微生物的种类,总结了微生物修复石油污染土壤的主要影响因素,阐述了微生物强化修复石油土壤的多种有效策略,提出了微生物强化修复石油污染的未来发展方向。     

低温微生物修复石油烃类污染土壤研究进展

耐冷菌、嗜冷菌等低温微生物广泛存在于极地、高山以及高纬度等土壤环境中,是石油烃类污染物在低温条件下降解与转化的重要微生物资源.利用低温微生物的独特优势,石油污染土壤的低温生物修复技术的研究成为当前热点领域.本文系统综述了低温石油烃降解菌的分类及冷适机制,低温微生物对不同类型石油烃组分的降解特征和降解机理,低温环境中接种降解菌、添加营养物质和表面活性剂等强化技术在石油污染土壤中生物修复的应用.以及微生物分子生物学技术在低温微生物降解石油烃的研究现状,为拓展我国石油污染土壤生物修复技术提供参考.     

群体感应在生物强化功能菌定殖及降解能力增强中的作用研究进展

由于难降解有机污染物和外界环境对水处理系统的冲击干扰,污水水质常出现不达标现象。引入外源含有相关功能基因并且具有基因水平转移能力的工程菌株进行生物强化处理是提高污水处理效能的有效措施。污水处理系统中存在能够分泌信号分子的菌体,菌间具有群体感应现象,当种群密度达到感应阈值时,菌体会通过释放信号分子来触发一些群体行为,从而激活相关基因的表达(如生物膜形成、生物发光、抗生素合成和毒力因子表达等)。早期的群体感应技术研究主要集中在信号传递学、微生物社会行为学和医学微生物领域,近年来,在水处理领域也开始有相继报道,研究表明群体感应在污水生物处理中发挥重要作用,并且影响生物强化菌株的定殖和污染物降解,因此群体感应行为调控是生物强化技术成效显著与否的关键因素。本文综述了群体感应及信号分子的作用机制、信号分子释放及存在的影响因素以及群体感应对菌株定殖、微生物群落结构和污染物去除的影响,并对从群体感应角度出发研究生物强化过程进行了展望,旨在为生物强化技术的有效实施及提升污水处理效能提供一种新思路,为深入理解生物强化过程中群体感应调控行为提供理论参考。     

海洋石油污染物的微生物降解与生物修复

石油是海洋环境的主要污染物 ,已经对海洋及近岸环境造成了严重的危害。微生物降解是海洋石油污染去除的主要途径。海洋石油污染物的微生物降解受石油组分与理化性质、环境条件以及微生物群落组成等多方面因素的制约 ,N和P营养的缺乏是海洋石油污染物生物降解的主要限制因子。在生物降解研究基础上发展起来的生物修复技术在海洋石油污染治理中发展潜力巨大 ,并且取得了一系列成果。介绍了海洋中石油污染物的来源、转化过程、降解机理、影响生物降解因素及生物修复技术等方面内容 ,强调了生物修复技术在治理海洋石油污染环境中的优势和重要性 ,指出目前生物修复技术存在的问题。     

微生物降解硝基芳烃及其卤代衍生物的研究进展

硝基芳烃化合物作为一种重要的化工原料,广泛应用于医药、染料、农药等化工产品的合成。在给人类社会带来空前的物质繁荣的同时,其造成的环境污染问题也成为人类社会面临的重要挑战之一。微生物在这些环境污染物的降解中起着重要的作用。近几十年,环境微生物工作者对微生物降解硝基芳香污染物的各个步骤,包括趋化感应、分解代谢及生物修复进行了大量的研究工作,获得了丰富的知识。本文综述了硝基芳烃及其卤代衍生物的微生物代谢途径、代谢机理、趋化及修复研究进展,并对本领域的研究进行了展望,有助于全面认知硝基芳烃污染物的微生物降解过程,为污染环境修复提供理论基础。     

微生物对砷的作用机理及利用真菌修复砷污染土壤的可行性

利用真菌修复砷污染土壤和水体具有很大的发展潜力,是环境科学领域研究的热点.环境中存在的砷虽然不能像有机污染物那样被微生物降解,但可以通过微生物对砷的氧化/还原、吸附/解吸、甲基化/去甲基化、沉淀/溶解等作用影响其生物有效性,从而达到降低环境中的砷毒害、修复砷污染环境的目的.本文阐述了微生物对砷的作用机理,综述了真菌对砷累积与挥发研究的最新进展,探讨了其在修复砷污染土壤方面的可行性,旨在为利用真菌来修复砷污染土壤提供理论依据.     

面向有机污染物消除的“微生物、植物、电”多效耦合作用机制及低能耗型修复技术

中欧合作项目"面向有机污染物消除的‘微生物、植物、电’多效耦合作用机制及低能耗型修复技术"是由中国国家自然科学基金委和欧盟共同资助的重大国际合作项目。该项目研究领域属于环境生物技术,研究团队包括5个中方单位和17个欧方单位,项目主要围绕新有机污染物的生物降解过程和机制、低能耗生物修复技术开展研究工作。项目执行2年来,在降解污染物的微生物资源、弱电介入增效生物降解和强化电子传递、微生物3D打印等方面取得了阶段性成果的同时,项目团队还开展了有效的交流和实质性合作。未来,项目团队将克服新冠疫情影响,强化中欧双方团队内部和团队之间的合作交流,全面实现项目科学目标,圆满完成国际合作任务。     

Application of DNA amplification fingerprinting (DAF) to mixed culture bioreactors

Summary The use of DNA amplification fingerprinting (DAF) as a tool for monitoring mixed microbial populations in bioreactors was evaluated. Short (8-mer or 10-mer) oligonucleotides were used to prime DNA extracts from various biological reactors during polymerase chain reaction (PCR) amplification. The reactors examined in this study included two sets of anaerobic stirred tank continuous flow bioreactors. One set of anaerobic reactors was operated under methanogenic conditions and one set was operated under sulfate-reducing conditions. The anaerobic reactor communities in the methanol-fed reactors showed extensive DAF homology. DAF was also applied to a fixed-film azo dye degrading reactor to examine the degree of uniformity of colonization of the substratum in representative regions of the reactor. This method is a quick and relatively inexpensive means of monitoring microbial community structure during biological processes. Since no cultivation of the sample is involved, the genetic profile of the community is not biased by outgrowth conditions. DAF profiles may be useful for comparisons of population changes over time or of bench-scale vs pilot-scale reactors but not adequate for assessing community diversity.     

Change in microbial communities in acetate- and glucose-fed microbial fuel cells in the presence of light

Power densities produced by microbial fuel cells (MFCs) in natural systems are changed by exposure to light through the enrichment of photosynthetic microorganisms. When MFCs with brush anodes were exposed to light (4000 lx), power densities increased by 8–10% for glucose-fed reactors, and 34% for acetate-fed reactors. Denaturing gradient gel electrophoresis (DGGE) profiles based on the 16S rRNA gene showed that exposure to high light levels changed the microbial communities on the anodes. Based on 16S rRNA gene clone libraries of light-exposed systems the anode communities using glucose were also significantly different than those fed acetate. Dominant bacteria that are known exoelectrogens were identified in the anode biofilm, including a purple nonsulfur (PNS) photosynthetic bacterium, Rhodopseudomonas palustris, and a dissimilatory iron-reducing bacterium, Geobacter sulfurreducens. Pure culture tests confirmed that PNS photosynthetic bacteria increased power production when exposed to high light intensities (4000 lx). These results demonstrate that power production and community composition are affected by light conditions as well as electron donors in single-chamber air-cathode MFCs.     

Testing the Efficiency of Biofilms Formed on Natural Substratum,Coyonoxtle (Opuntia Imbricata), for the Anaerobic Degradation of Aromatic Compounds

In this study, previously developed anaerobic microbial consortia capable of degrading aromatic compounds were used to develop biofilms on a natural material, coyonoxtle (Opuntia imbricata), which is abundantly available in North Mexico. The developed biofilms were evaluated for their efficiency in the biodegradation of different aromatic compounds, viz., phenol, catechol, 4‐aminobenzoic acid and p‐phenylenediamine in batch reactors. It was observed that in reactors with biofilms a more than 90 % COD removal and a concomitant production of methane could be obtained. But the rate of COD removal and methane production varied depending upon the type of biofilm used. Rumen‐derived biofilms demonstrated a lag phase of 7 to 14 days, whereas sludge‐derived biofilms exhibited a lag phase of more than three weeks. Between the biofilms from two sources, rumen‐derived biofilms showed a higher COD removal and methane production than sludge‐derived biofilms. When biofilm reactors were compared with reactors containing freely suspended consortia, it was evident that both rumen– and sludge‐derived biofilm reactors exhibited a two‐fold higher COD removal and methane production. Based on the results obtained, it can be concluded that coyonoxtle has the potential for use as a substratum.     

Comparison of anode bacterial communities and performance in microbial fuel cells with different electron donors

Microbial fuel cells (MFCs) harness the electrochemical activity of certain microbes for the production of electricity from reduced compounds. Characterizations of MFC anode biofilms have collectively shown very diverse microbial communities, raising ecological questions about competition and community succession within these anode-reducing communities. Three sets of triplicate, two-chamber MFCs inoculated with anaerobic sludge and differing in energy sources (acetate, lactate, and glucose) were operated to explore these questions. Based on 16S rDNA-targeted denaturing gradient gel electrophoresis (DGGE), all anode communities contained sequences closely affiliated with Geobacter sulfurreducens (>99% similarity) and an uncultured bacterium clone in the Bacteroidetes class (99% similarity). Various other Geobacter-like sequences were also enriched in most of the anode biofilms. While the anode communities in replicate reactors for each substrate generally converged to a reproducible community, there were some variations in the relative distribution of these putative anode-reducing Geobacter-like strains. Firmicutes were found only in glucose-fed MFCs, presumably serving the roles of converting complex carbon into simple molecules and scavenging oxygen. The maximum current density in these systems was negatively correlated with internal resistance variations among replicate reactors and, likely, was only minimally affected by anode community differences in these two-chamber MFCs with high internal resistance.     

Degradation of pentachlorophenol with the presence of fermentable and non-fermentable co-substrates in a microbial fuel cell

Pentachlorophenol (PCP) was more rapidly degraded in acetate and glucose-fed microbial fuel cells (MFCs) than in open circuit controls, with removal rates of 0.12 ± 0.01 mg/Lh (14.8 ± 1.0 mg/g-VSS-h) in acetate-fed, and 0.08 ± 0.01 mg/L h (6.9 ± 0.8 mg/g-VSS-h) in glucose-fed MFCs, at an initial PCP concentration of 15 mg/L. A PCP of 15 mg/L had no effect on power generation from acetate but power production was decreased with glucose. Coulombic balances indicate the predominant product was electricity (16.1 ± 0.3%) in PCP-acetate MFCs, and lactate (19.8 ± 3.3%) in PCP-glucose MFCs. Current generation accelerated the removal of PCP and co-substrates, as well as the degradation products in both PCP-acetate and PCP-glucose reactors. While 2,3,4,5-tetrachlorophenol was present in both reactors, tetrachlorohydroquinone was only found in PCP-acetate MFCs. These results demonstrate PCP degradation and power production were affected by current generation and the type of electron donor provided.     

Anode microbial communities produced by changing from microbial fuel cell to microbial electrolysis cell operation using two different wastewaters

Conditions in microbial fuel cells (MFCs) differ from those in microbial electrolysis cells (MECs) due to the intrusion of oxygen through the cathode and the release of H₂ gas into solution. Based on 16S rRNA gene clone libraries, anode communities in reactors fed acetic acid decreased in species richness and diversity, and increased in numbers of Geobacter sulfurreducens, when reactors were shifted from MFCs to MECs. With a complex source of organic matter (potato wastewater), the proportion of Geobacteraceae remained constant when MFCs were converted into MECs, but the percentage of clones belonging to G. sulfurreducens decreased and the percentage of G. metallireducens clones increased. A dairy manure wastewater-fed MFC produced little power, and had more diverse microbial communities, but did not generate current in an MEC. These results show changes in Geobacter species in response to the MEC environment and that higher species diversity is not correlated with current.     

Adaptation to high current using low external resistances eliminates power overshoot in microbial fuel cells

One form of power overshoot commonly observed with mixed culture microbial fuel cells (MFCs) is doubling back of the power density curve at higher current densities, but the reasons for this type of overshoot have not been well explored. To investigate this, MFCs were acclimated to different external resistances, producing a range of anode potentials and current densities. Power overshoot was observed for reactors acclimated to higher (500 and 5000 Ω) but not lower (5 and 50 Ω) resistances. Acclimation of the high external resistance reactors for a few cycles to low external resistance (5 Ω), and therefore higher current densities, eliminated power overshoot. MFCs initially acclimated to low external resistances exhibited both higher current in cyclic voltammograms (CVs) and higher levels of redox activity over a broader range of anode potentials (-0.4 to 0 V; vs. a Ag/AgCl electrode) based on first derivative cyclic voltammetry (DCV) plots. Reactors acclimated to higher external resistances produced lower current in CVs, exhibited lower redox activity over a narrower anode potential range (-0.4 to -0.2 V vs. Ag/AgCl), and failed to produce higher currents above ～-0.3 V (vs. Ag/AgCl). After the higher resistance reactors were acclimated to the lowest resistance they also exhibited similar CV and DCV profiles. Our findings show that to avoid overshoot, prior to the polarization and power density tests the anode biofilm must adapt to low external resistances to be capable of higher currents.     

Nitrilotriacetic acid degradation under microbial fuel cell environment

The removal of nitrilotriacetic acid (NTA) was studied under anaerobic conditions using oligotrophic and copiotrophic microbial fuel cells (MFCs) as a novel wastewater treatment process. Over 85% of NTA was removed from oligotrophic MFCs enriched and maintained with fuel containing NTA, whilst the value was around 20% in oligotrophic MFCs fed with NTA-free fuel, and in copiotrophic MFCs enriched with NTA containing fuel. The oligotrophic MFCs generated current with concomitant utilization of NTA when served as the sole organic compound, suggesting that NTA is oxidized its suitability as fuel in the MFCs.     

Anaerobic/aerobic conditions and biostimulation for enhanced chlorophenols degradation in biocathode microbial fuel cells

Anaerobic/aerobic conditions affected bacterial community composition and the subsequent chlorophenols (CPs) degradation in biocathode microbial fuel cells (MFCs). Bacterial communities acclimated with either 4-chlorophenol (4-CP) or 2,4-dichlorophenol (2,4-DCP) under anaerobiosis can degrade the respective substrates more efficiently than the facultative aerobic bacterial communities. The anaerobic bacterial communities well developed with 2,4-DCP were then adapted to 2,4,6-trichlorophenol (2,4,6-TCP) and successfully stimulated for enhanced 2,4,6-TCP degradation and power generation. A 2,4,6-TCP degradation rate of 0.10 mol/m³/d and a maximum power density of 2.6 W/m³ (11.7 A/m³) were achieved, 138 and 13 % improvements, respectively compared to the controls with no stimulation. Bacterial communities developed with the specific CPs under anaerobic/aerobic conditions as well as the stimulated biofilm shared some dominant genera and also exhibited great differences. These results provide the most convincing evidence to date that anaerobic/aerobic conditions affected CPs degradation with power generation from the biocathode systems, and using deliberate substrates can stimulate the microbial consortia and be potentially feasible for the selection of an appropriate microbial community for the target substrate (e.g. 2,4,6-TCP) degradation in the biocathode MFCs.     

Anaerobic Reactor Design Concepts for the Treatment of Domestic Wastewater

Since the earlier anaerobic treatment systems, the design concepts were improved from classic reactors like septic tanks and anaerobic ponds, to modern high rate reactor configurations like anaerobic filters, UASB, EGSB, fixed film fluidized bed and expanded bed reactors, and others. In this paper, anaerobic reactors are evaluated considering the historical evolution and types of wastewaters. The emphasis is on the potential for application in domestic sewage treatment, particularly in regions with a hot climate. Proper design and operation can result in a high capacity and efficiency of organic matter removal using single anaerobic reactors. Performance comparison of anaerobic treatment systems is presented based mostly on a single but practical parameter, the hydraulic retention time. Combined anaerobic reactor systems as well as combined anaerobic and non-anaerobic systems are also presented.