Treatment of alcohol distillery wastewater using a Bacteroidetes-dominant thermophilic microbial fuel cell

Simultaneous electricity generation and distillery wastewater (DWW) treatment were accomplished using a thermophilic microbial fuel cell (MFC). The results suggest that thermophilic MFCs, which require less energy for cooling the DWW, can achieve high efficiency for electricity generation and also reduce sulfate along with oxidizing complex organic substrates. The generated current density (2.3 A/m(2)) and power density (up to 1.0 W/m(2)) were higher than previous wastewater-treating MFCs. The significance of the high Coulombic efficiency (CE; up to 89%) indicated that electrical current was the most significant electron sink in thermophilic MFCs. Bacterial diversity based on pyrosequencing of the 16S rRNA gene revealed that known Deferribacteres and Firmicutes members were not dominant in the thermophilic MFC fed with DWW; instead, uncharacterized Bacteroidetes thermophiles were up to 52% of the total reads in the anode biofilm. Despite the complexity of the DWW, one single bacterial sequence (OTU D1) close to an uncultured Bacteriodetes bacterium became predominant, up to almost 40% of total reads. The proliferation of the D1 species was concurrent with high electricity generation and high Coulombic efficiency.     

Continuous electricity generation from domestic wastewater and organic substrates in a flat plate microbial fuel cell

A microbial fuel cell (MFC) is a device that converts organic matter to electricity using microorganisms as the biocatalyst. Most MFCs contain two electrodes separated into one or two chambers that are operated as a completely mixed reactor. In this study, a flat plate MFC (FPMFC) was designed to operate as a plug flow reactor (no mixing) using a combined electrode/proton exchange membrane (PEM) system. The reactor consisted of a single channel formed between two nonconductive plates that were separated into two halves by the electrode/PEM assembly. Each electrode was placed on an opposite side of the PEM, with the anode facing the chamber containing the liquid phase and the cathode facing a chamber containing only air. Electricity generation using the FPMFC was examined by continuously feeding a solution containing wastewater, or a specific substrate, into the anode chamber. The system was initially acclimated for 1 month using domestic wastewater orwastewater enriched with a specific substrate such as acetate. Average power density using only domestic wastewater was 72+/-1 mW/m2 at a liquid flow rate of 0.39 mL/min [42% COD (chemical oxygen demand) removal, 1.1 h HRT (hydraulic retention time)]. At a longer HRT = 4.0 h, there was 79% COD removal and an average power density of 43+/-1 mW/m2. Power output was found to be a function of wastewater strength according to a Monod-type relationship, with a half-saturation constant of Ks = 461 or 719 mg COD/L. Power generation was sustained at high rates with several organic substrates (all at approximately 1000 mg COD/L), including glucose (212+/-2 mW/ m2), acetate (286+/-3 mW/m2), butyrate (220+/-1 mW/ m2), dextran (150+/-1 mW/m2), and starch (242+/-3 mW/ m2). These results demonstrate the versatility of power generation in a MFC with a variety of organic substrates and show that power can be generated at a high rate in a continuous flow reactor system.     

Anaerobic treatment performance and microbial population of thermophilic upflow anaerobic filter reactor treating awamori distillery wastewater

Distillery wastewater from awamori making was anaerobically treated for one year using thermophilic upflow anaerobic filter (UAF) reactors packed with pyridinium group-containing nonwoven fabric material. The microbial structure and spatial distribution of microorganisms on the support material were characterized using molecular biological methods. The reactor steadily achieved a high TOC loading rate of 18 g/l/d with approximately 80% TOC removal efficiency when non-diluted wastewater was fed. The maximum TOC loading rate increased to 36 g/l/d when treating thrice-diluted wastewater. However, the TOC removal efficiency and gas evolution rate decreased compared with that when non-diluted wastewater was used. Methanogens closely related to Methanosarcina thermophila and Methanoculleus bourgensis and bacteria in the phyla Firmicutes and Bacteroidetes were predominant methanogens and bacteria in the thermophilic UFA reactor, as indicated by 16S rRNA gene clone analysis. Fluorescence in situ hybridization (FISH) results showed that a large quantity of bacterial cells adhered throughout the whole support, and Methanosarcina-like methanogens existed mainly in the relative outside region while Methanoculleus cells were located in the relative inner part of the support. The support material used proved to be an excellent carrier for microorganisms, and a UAF reactor using this kind of support can be used for high-rate treatment of awamori/shochu distillery wastewater.     

Tubular microbial fuel cells for efficient electricity generation

A tubular, single-chambered, continuous microbial fuel cell (MFC) that generates high power outputs using a granular graphite matrix as the anode and a ferricyanide solution as the cathode is described. The maximal power outputs obtained were 90 and 66 W m(-3) net anodic compartment (NAC) (48 and 38 W m(-3) total anodic compartment (TAC)) for feed streams based on acetate and glucose, respectively, and 59 and 48 W m(-3) NAC for digester effluent and domestic wastewater, respectively. For acetate and glucose, the total Coulombic conversion efficiencies were 75 +/- 5% and 59 +/- 4%, respectively, at loading rates of 1.1 kg chemical oxygen demand m(-3) NAC volume day(-1). When wastewater was used, of the organic matter effectively removed (i.e., 22% at a loading of 2 kg organic matter m(-3) NAC day(-1)), up to 96% was converted to electricity on a Coulombic basis. The lower overall efficiency of the wastewater-treating reactors is related to the presence of nonreadily biodegradable organics and the interference of alternative electron acceptors such as sulfate present in the wastewater. To further improve MFCs, focus has to be placed on the enhanced conversion of nonrapidly biodegradable material and the better directing of the anode flow toward the electrode instead of to alternative electron acceptors. Also the use of sustainable, open-air cathodes is a critical issue for practical implementation.     

Integrating forward osmosis into microbial fuel cells for wastewater treatment, water extraction and bioelectricity generation

A novel osmotic microbial fuel cell (OsMFC) was developed by using a forward osmosis (FO) membrane as a separator. The performance of the OsMFC was examined with either NaCl solution or artificial seawater as a catholyte (draw solution). A conventional MFC with a cation exchange membrane was also operated in parallel for comparison. It was found that the OsMFC produced more electricity than the MFC in both batch operation (NaCl solution) and continuous operation (seawater), likely due to better proton transport with water flux through the FO membrane. Water flux from the anode into the cathode was clearly observed with the OsMFC but not in the MFC. The solute concentration of the catholyte affected both electricity generation and water flux. These results provide a proof of concept that an OsMFC can simultaneously accomplish wastewater treatment, water extraction (from the wastewater), and electricity generation. The potential applications of the OsMFC are proposed for either water reuse (linking to reverse osmosis for reconcentration of draw solution) or seawater desalination (connecting with microbial desalination cells for further wastewater treatment and desalination).     

Production of electricity during wastewater treatment using a single chamber microbial fuel cell

Microbial fuel cells (MFCs) have been used to produce electricity from different compounds, including acetate, lactate, and glucose. We demonstrate here that it is also possible to produce electricity in a MFC from domestic wastewater, while atthe same time accomplishing biological wastewater treatment (removal of chemical oxygen demand; COD). Tests were conducted using a single chamber microbial fuel cell (SCMFC) containing eight graphite electrodes (anodes) and a single air cathode. The system was operated under continuous flow conditions with primary clarifier effluent obtained from a local wastewater treatment plant. The prototype SCMFC reactor generated electrical power (maximum of 26 mW m(-2)) while removing up to 80% of the COD of the wastewater. Power output was proportional to the hydraulic retention time over a range of 3-33 h and to the influent wastewater strength over a range of 50-220 mg/L of COD. Current generation was controlled primarily by the efficiency of the cathode. Optimal cathode performance was obtained by allowing passive air flow rather than forced air flow (4.5-5.5 L/min). The Coulombic efficiency of the system, based on COD removal and current generation, was < 12% indicating a substantial fraction of the organic matter was lost without current generation. Bioreactors based on power generation in MFCs may represent a completely new approach to wastewater treatment. If power generation in these systems can be increased, MFC technology may provide a new method to offset wastewater treatment plant operating costs, making advanced wastewater treatment more affordable for both developing and industrialized nations.     

Effect of temperature on microbial community of a glucose-degrading methanogenic consortium under hyperthermophilic chemostat cultivation

We continuously fed an anaerobic chemostat with synthetic wastewater containing glucose as the sole source of carbon and energy to study the effects of temperature on the microbial community under hyperthermophilic (65-80 degrees C) conditions. Methane was produced normally up to 77.5 degrees C at a dilution rate of 0.025 d(-1). However, the concentration of microorganisms and the rate of gas production decreased with increasing operation temperature. The microbial community in the chemostat at various temperatures was analyzed based on the 16S rRNA gene using molecular biological techniques including clone library analysis and denaturing gradient gel electrophoresis (DGGE). Aceticlastic methanogens related to Methanosarcina thermophila were detected at 65 degrees C and hydrogenotrophilic methanogens related to Methanothermobacter thermautotrophicus were the dominant methanogens between 70 degrees C to 77.5 degrees C. Bacteria related to Clostridium stercorarium and Thermoanaerobacter subterraneus comprised the dominant glucose-fermenting bacteria at temperatures of 65 degrees C and above, respectively. Bacteria related to Thermacetogenium phaeum and to Tepidiphilus margaritifer and Petrobacter succinatimandens were the dominant acetate-oxidizing bacteria at 70 degrees C and at 75-77.5 degrees C, respectively. The results suggested that, at temperatures of 70 degrees C and above, methane production via the aceticlastic pathway was negligible and indirect methanogenesis from acetate was dominant. Since acetate oxidation is a rate limiting step and a higher temperature favors the hydrolysis and acid formation, a two stage fermentation process, acidogenic and methanogenic fermentation stages operated under different temperatures, should be more suitable for the thermophilic anaerobic treatment at temperatures above 65 degrees C.     

Concurrent desalination and hydrogen generation using microbial electrolysis and desalination cells

The versatility of bioelectrochemical systems (BESs) makes them promising for various applications, and good combinations could make the system more applicable and economically effective. An integrated BES called microbial electrolysis and desalination cell (MEDC) was developed to concurrently desalinate salt water, produce hydrogen gas, and potentially treat wastewater. The reactor is divided into three chambers by inserting a pair of ion exchange membranes, with each chamber serving one of the three functions. With an added voltage of 0.8 V, lab scale batch study shows the MEDC achieved the highest H(2) production rate of 1.5 m(3)/m(3) d (1.6 mL/h) from the cathode chamber, while also removing 98.8% of the 10 g/L NaCl from the middle chamber. The anode recirculation alleviated pH and high salinity inhibition on bacterial activity and further increased system current density from 87.2 to 140 A/m(3), leading to an improved desalination rate by 80% and H(2) production by 30%. Compared to slight changes in desalination, H(2) production was more significantly affected by the applied voltage and cathode buffer capacity, suggesting cathode reactions were likely affected by the external power supply in addition to the anode microbial activity.     

Microbial communities in the garbage composting with rice hull as an amendment revealed by culture-dependent and -independent approaches

The diversity and succession of microbial communities during the garbage composting with rice hull as an amendment were studied by denaturing gradient gel electrophoresis (DGGE) and clone library analysis of PCR-amplified 16S ribosomal DNA (rDNA) with universal primers. Based on temperature changes, the composting process could be divided into thermophilic, cooling-down, and maturing stages. The DGGE profiles and clone library analysis revealed that the microbial community drastically changed during the composting process from the thermophilic to the maturing stages. The dominant bacterial group changed from the phylum Firmicutes in the thermophilic stage to the phylum Bacteroidetes in the maturing stage. This change in microbial communities may be significant for the composting process. The diversity of cultivated bacteria isolated from samples taken at various stages of the composting process was low. A total of 87 isolates were classified as belonging to only four different groups. These groups were also detected in the DGGE profiles and by the clone library analysis. Our study indicated that a combination of culture-dependent and -independent approaches could be very useful for monitoring both bacterial diversity and the succession of communities during the composting process. This study would be beneficial for assessing the ecological consequences of disposal of organic waste.     

Enhanced electricity production by use of reconstituted artificial consortia of estuarine bacteria grown as biofilms

Microbial fuel cells (MFCs) can convert organic compounds directly into electricity by catalytic oxidation, and although MFCs have attracted considerable interest, there is little information on the electricity-generating potential of artificial bacterial biofilms. We have used acetate-fed MFCs inoculated with sediment, with two-chamber bottles and carbon cloth electrodes to deliver a maximum power output of ~175 mW · m(-2) and a stable power output of ~105 mW · m(-2). Power production was by direct transfer of electrons to the anode from bacterial consortia growing on the anode, as confirmed by cyclic voltammetry (CV) and scanning electron microscopy (SEM). Twenty different species (74 strains) of bacteria were isolated from the consortium under anaerobic conditions and cultured in the laboratory, of which 34% were found to be exoelectrogens in single-species studies. Exoelectrogenesis by members of the genera Vibrio , Enterobacter , and Citrobacter and by Bacillus stratosphericus was confirmed, by use of culture-based methods, for the first time. An MFC with a natural bacterial consortium showed higher power densities than those obtained with single strains. In addition, the maximum power output could be further increased to ~200 mW · m(-2) when an artificial consortium consisting of the best 25 exoelectrogenic isolates was used, demonstrating the potential for increased performance and underlying the importance of artificial biofilms for increasing power output.     

芝麻香型白酒高温大曲嗜热细菌群落研究

利用高温筛选和传统培养方法,借助于核糖体DNA扩增片段限制性内切酶(ARDRA)分型、分子鉴定以及系统发育分析技术,研究了芝麻香型白酒高温大曲嗜热细菌群落结构。结果显示,55℃高温筛选获得的85株嗜热细菌分属于4个菌属,分别为Thermoactinomyces sp.,Bacillus sp.,Schlegelella sp.以及Streptomyces sp.,其中第1优势菌为Thermoactinomyces vulgaris,丰度为69.41%。该研究首次报道了芝麻香型白酒高温大曲中的嗜热细菌类群,为进一步探索其功能性以及建立其与芝麻香型白酒风味的相关性奠定了基础。     

贮存温度对原料羊乳中微生物的影响

对不同贮存温度下原料羊乳中微生物变化规律进行研究,研究表明,原料羊乳在3℃下贮存36h,乳样中菌落总数、大肠菌群、嗜热菌、蛋白分解菌和脂肪分解菌变化不显著(p>0.05),嗜冷菌变化差异显著(p<0.05);在10℃下贮存24h后,乳样中菌落总数、大肠菌群、嗜冷菌变化差异显著(p<0.05),嗜热菌、蛋白分解菌和脂肪分解菌变化不显著(p>0.05);当贮存温度为37℃和25℃时,分别贮存6h和12h以后乳样中的菌落总数、大肠菌群、嗜热菌、蛋白分解菌和脂肪分解菌变化差异显著(p<0.05),而嗜冷菌变化差异不显著(p>0.05)。随着贮存温度的升高和贮存时间的延长,原料羊乳中微生物数量增加。在原料羊乳的贮存和运输过程中,应尽可能将贮存温度控制在3℃,贮存时间不应该超过36h,以提高原料羊乳的卫生质量。      

Characterization of microbial fuel cells at microbially and electrochemically meaningful time scales

The variable biocatalyst density in a microbial fuel cell (MFC) anode biofilm is a unique feature of MFCs relative to other electrochemical systems, yet performance characterizations of MFCs typically involve analyses at electrochemically relevant time scales that are insufficient to account for these variable biocatalyst effects. This study investigated the electrochemical performance and the development of anode biofilm architecture under different external loadings, with duplicate acetate-fed single-chamber MFCs stabilized at each resistance for microbially relevant time scales. Power density curves from these steady-state reactors generally showed comparable profiles despite the fact that anode biofilm architectures and communities varied considerably, showing that steady-state biofilm differences had little influence on electrochemical performance until the steady-state external loading was much larger than the reactor internal resistance. Filamentous bacteria were dominant on the anodes under high external resistances (1000 and 5000 Ω), while more diverse rod-shaped cells formed dense biofilms under lower resistances (10, 50, and 265 Ω). Anode charge transfer resistance decreased with decreasing fixed external resistances, but was consistently 2 orders of magnitude higher than the resistance at the cathode. Cell counting showed an inverse exponential correlation between cell numbers and external resistances. This direct link of MFC anode biofilm evolution with external resistance and electricity production offers several operational strategies for system optimization.     

烤烟内生高温菌YYFG3的分离鉴定及所产蛋白酶活性

通过固体分离培养基的分离培养和牛奶琼脂鉴别培养基的鉴别初筛,从烟草(Nicotiana tabacum L.)的初烤烟叶中分离到一株嗜热产蛋白酶菌株,编号为YYFG3,其生长温度范围是30℃-65℃,最适生长温度55℃左右,对pH的耐受范围是5-9,最适范围是6-7;在发酵产酶培养基中,56℃、180 r/min条件下发酵32 h的蛋白酶活力达到最大值35.3 U/mL,故将YYFG3定性为产蛋白酶高温菌株。通过光学显微镜和扫描电子显微镜对该菌株形态特征的观察、相关生化特性的测定、16S rDNA的克隆测序以及对菌株分子遗传进化树的构建,确定菌株YYFG3隶属于土芽孢杆菌属Geobacillus,暂将其命名为Geobacillus sp.YYFG3。菌株YYFG3可作为产蛋白酶高温微生物诱变育种和全基因组育种的良好材料,具有良好的开发应用潜力。      

腌制苋菜梗的微生物菌群结构及其品质

腌制苋菜梗是浙东传统的特色腌制食品,了解其细菌种群结构并探讨对亚硝酸盐等理化品质的影响,以确保腌制食品的安全性。采用16S rDNA基因克隆文库的方法,对腌制成熟的苋菜梗中细菌组成结构多样性进行了分析,共检测出了乳杆菌、类香菌、弓形杆菌等6个菌属,其中乳杆菌属占优势为总数的83.9%。与此同时,测定了腌制苋菜梗体系亚硝酸盐等一些理化指标,腌制成熟时pH值为4.35,盐度为5.5,亚硝酸盐质量分数为3.99mg/kg(未超标),细菌和乳酸菌浓度分别为8.8×106 CFU/mL和1.6×106 CFU/mL。     

环介导等温扩增技术检测酸奶中嗜酸乳杆菌

目的建立环介导等温扩增法(loop-mediated isothermal amplification,LAMP)检测酸奶中嗜酸乳杆菌。方法以嗜酸乳杆菌16S r RNA保守区的基因序列为靶序列设计引物,优化建立LAMP反应体系和程序,并研究引物的特异性,同时确定嗜酸乳杆菌的灵敏度和检出限。结果本方法可通过凝胶电泳和离心后焦磷酸镁白色沉淀检测反应结果,检测时间为5.5 h,灵敏度为62 CFU/m L,人工污染酸奶样品的检出限为120 CFU/m L,12株非嗜酸乳杆菌细菌非特异检测结果均为100%。结论该方法灵敏性好、特异性强、操作简单、耗时短,可适合于酸奶中的嗜酸乳杆菌的快速测定。     

Biological denitrification in microbial fuel cells

Microbial fuel cells (MFCs) that remove carbon as well as nitrogen compounds out of wastewater are of special interest for practice. We developed a MFC in which microorganisms in the cathode performed a complete denitrification by using electrons supplied by microorganisms oxidizing acetate in the anode. The MFC with a cation exchange membrane was designed as a tubular reactor with an internal cathode and was able to remove up to 0.146 kg NO(3-)-N m(-3) net cathodic compartment (NCC) d(-1) (0.080 kg NO(3-)-N m(-3) total cathodic compartment d(-1) (TCC)) at a current of 58 A m(-3) NCC (32 A m(-3) TCC) and a cell voltage of 0.075 V. The highest power output in the denitrification system was 8 W m(-3) NCC (4 W m(-3) TCC) with a cell voltage of 0.214 V and a current of 35 A m(-3) NCC. The denitrification rate and the power production was limited bythe cathodic microorganisms, which only denitrified significantly at a cathodic electrode potential below 0 V versus standard hydrogen electrode (SHE). This is, to our knowledge, the first study in which a MFC has both a biological anode and cathode performing simultaneous removal of an organic substrate, power production, and complete denitrification without relying on H2-formation or external added power.     

Characterization of the microbial community in three types of fermentation starters used for Chinese liquor production

This study examined and compared the microbial community in three typical fermentation starters (called as Daqu, Xiaoqu, and Fuqu in China) used for liquor production by analysing the 16S and 18S rRNA gene clone library. The results show that the microbial diversity in the three types of fermentation starters (JiuQu) differs significantly. The bacterial species in Daqu and Fuqu were mainly thermophilic or thermotolerant. In Daqu, the dominant bacterial species were Thermoactinomyces sanguinis (53.85%) and Pantoea agglomerans (19.23%), followed by uncultured bacteria (15.39%). The lactic acid bacterium Weissella cibaria (50%) and a member of Enterobacteriaceae, Enterobacter ludwigii (10%), were the dominant bacterial species in Xiaoqu. Low abundances of other bacteria, including Deinococcus radiodurans, Corynebacterium variabile and Acinetobacter baumannii, were reported for Xiaoqu. Enterococcus faecium, Clostridium beijerinckii and Bacillus cereus were observed in Fuqu and accounted for 46.67, 23.33 and 16.67% of the total bacteria identified, respectively. Fungal diversity was high in Daqu and consisted exclusively of thermophilic moulds, such as Aspergillus glaucus (62.5%), Thermomyces lanuginosus (12.5%) and Thermoascus crustaceus (12.5%). Only two fungal species were reported for Fuqu and Xiaoqu and both contained the mould Rhizopus oryzae. Saccharomyces cerevisiae and the non‐Saccharomyces yeast (Saccharomycopsis fibuligera) were also identified in Fuqu and Xiaoqu, respectively. This finding suggests that microbial community structure in JiuQu starters is the key factor to determine the variety of flavours. Copyright © 2015 The Institute of Brewing & Distilling     

阳电极面积对微生物燃料电池产电性能的影响

微生物燃料电池（MFC）最具应用前景之一是处理废水的同时能够产生电能。以糖蜜废水作为阳极基质,以金属离子的电镀废水做阴极溶液,研究了双室微生物燃料电池不同电极面积对产电性能和COD的影响。结果发现,当外电阻为300Q时,大反应器微生物燃料电池A．（阳极面积为78．15cm^2）及小反应器微生物燃料电池～（阳极面积为76．8cm^2）最大功率密度分别为0．28mW／cm^2和0．22mW／cm^2。在前200个小时内,A：电池在第60个小时时产生最大电压71．1mV和最大电流189．5μA,A,在第190个小时时产生最大电压81．1mV和最大电流228．1μA。同时,当Zn^2＋作阴极溶液时,小反应器微生物燃料电池阳极溶液的COD去除率在1．5％到7．02％之间,大反应器微生物燃料电池阳极溶液的COD去除率在0到14．96％之间。阴极中Zn^2＋去除率A1中为28．6％,A2为21．2％。     

Denitrifying polyphosphate accumulating organisms population and nitrite reductase gene diversity shift in a DEPHANOX-type activated sludge system fed with municipal wastewater

Enhanced biological phosphorus removal (EBPR) is a widely applied method for nutrients removal, although little is known about the key genes regulating the complex biochemical transformations occurring in activated sludge during phosphorus removal. In the present study, the nitrite reductase gene (nirS) diversity and the denitrifying polyphosphate accumulating organisms (DPAOs) population, grown in a bench scale, two-sludge, continuous flow plant, operating for biological anoxic phosphorus removal (DEPHANOX-type), fed with municipal wastewater, were examined by means of physicochemical analyses and the application of molecular techniques. The DEPHANOX configuration highly influenced biomass phosphorus as well as polyhydroxyalkanoates content and facilitated the enrichment of the DPAOs population. The application of double probe fluorescent in situ hybridization (double probe FISH) technique revealed that DPAOs comprised 20% of the total bacterial population. Based on clone libraries construction and nirS gene sequencing analysis, a pronounced shift in denitrifying bacteria diversity was identified during activated sludge acclimatization. Moreover, nirS gene sequences distinct from those detected in any known bacterial strain or environmental clone were identified. This is the first report studying the microbial properties of activated sludge in a DEPHANOX-type system using molecular techniques.