Biogas production and microbial community change during the Co-digestion of food waste with chinese silver grass in a single-stage anaerobic reactor

Chinese silver grass (CSG), a potential subtropical energy crop, was investigated as a co-substrate to enhance the anaerobic digestion of food waste for municipal solid waste treatment. Results showed that 88.1% of food wastes were degraded using CSG as a co-substrate with 45 days of digestion, where the food waste, CSG, and sludge on VS/TS/working volume was 93.14 g/111.55 g/1 L, in which the average biogas production was at 429.3 L/kg solids, and the average methane content was around 60%. During the digestion, the concentrations of ammonium and free ammonia gradually increased to 1448.2 and 265.2 mg/L respectively, without any significant inhibitory effects on biogas production, which is probably due to the buffering effects of CSG. Microbial community analysis showed that microorganisms from the class of Firmicutes and Bacteroidetes were dominant during digestion, and that the microbial community diversity increased with active methanogenesis, suggesting that the addition of substrates contribute to the increase of microbial diversity, and could be beneficial for biogas production. Therefore, using CSG as a co-substrate in the single-stage food waste anaerobic digestion system is a potential simple method to convert CSG into renewable energy and to simultaneously improve food waste treatment.     

Analysis of a microbial community associated with polychlorinated biphenyl degradation in anaerobic batch reactors

The degradation of polychlorinated biphenyls (PCBs) was investigated under fermentative-methanogenic conditions for up to 60 days in the presence of anaerobic biomass from a full-scale UASB reactor. The low methane yields in the PCBs-spiked batch reactors suggested that the biomass had an inhibitory effect on the methanogenic community. Reactors containing PCBs and co-substrates (ethanol/sodium formate) exhibited substantial PCB reductions from 0.7 to 0.2 mg mL^?1. For the Bacteria domain, the PCBs-spiked reactors were grouped with the PCB-free reactors with a similarity of 55 %, which suggested the selection of a specific population in the presence of PCBs. Three genera of bacteria were found exclusively in the PCB-spiked reactors and were identified using pyrosequencing analysis, Sedimentibacter, Tissierela and Fusibacter. Interestingly, the Sedimentibacter, which was previously correlated with the reductive dechlorination of PCBs, had the highest relative abundance in the R_CS-PCB (7.4 %) and R_CS-PCB-PF (12.4 %) reactors. Thus, the anaerobic sludge from the UASB reactor contains bacteria from the Firmicutes phylum that are capable of degrading PCBs.     

Effects of glucose overloading on microbial community structure and biogas production in a laboratory-scale anaerobic digester

This study characterizes the response of the microbial communities of a laboratory-scale mesophilic biogas process, fed with a synthetic substrate based on cellulose and egg albumin, to single pulses of glucose overloading (15 or 25 times the daily feed based on VS). The microbial biomass and community structure were determined from analyses of membrane phospholipids. The ratio between phospholipid fatty acids (PLFAs; eubacteria and eucaryotes) and di-ethers (PLEL; archaea) suggested that methanogens constituted 4-8% of the microbial biomass. The glucose addition resulted in transient increases in the total biomass of eubacteria while there were only small changes in community structure. The total gas production rate increased, while the relative methane content of the biogas and the alkalinity decreased. However, the biomass of methanogens was not affected by the glucose addition. The results show that the microbial communities of biogas processes can respond quickly to changes in the feeding rate. The glucose overload resulted in a transient general stimulation of degradation rates and almost a doubling of eubacterial biomass, although the biomass increase corresponded to only 7% of the glucose C added.     

Process stability and microbial community structure in anaerobic hydrogen-producing microflora from food waste containing kimchi

Hydrogen production by the dark fermentation of food wastes is an economic and environmentally friendly technology to produce the clean energy source as well as to treat the problematic wastes. However, the long-term operations of the continuous anaerobic reactor for fermentative hydrogen production were frequently unstable. In this study, the structure of microbial community within the anaerobic reactor during unstable hydrogen production was examined by denaturing gradient gel electrophoresis (DGGE) and terminal restriction fragment length polymorphism (T-RFLP) techniques. The changes in microbial community from H(2)-producing Clostridium spp. to lactic acid-producing Lactobacillus spp. were well coincident with the unexpected process failures and the changes of metabolites concentrations in the effluent of the anaerobic reactor. As the rate of hydrogen production decreased, effluent lactic acid concentration increased. Low rate of hydrogen production and changes in microbial community were related to the 'kimchi' content and storage temperature of food waste feed solution. After low temperature control of the storage tank of the feed solution, any significant change in microbial community within the anaerobic reactor did not occur and the hydrogen production was very stably maintained for a long time.     

Changes in the microbial community during repeated anaerobic microbial dechlorination of pentachlorophenol

Pentachlorophenol (PCP) has been widely used as a pesticide in paddy fields and has imposed negative ecological effect on agricultural soil systems, which are in typically anaerobic conditions. In this study, we investigated the effect of repeated additions of PCP to paddy soil on the microbial communities under anoxic conditions. Acetate was added as the carbon source to induce and accelerate cycles of the PCP degradation. A maximum degradation rate occurred at the 11th cycle, which completely transformed 32.3 μM (8.6 mg L^?1) PCP in 5 days. Illumina high throughput sequencing of 16S rRNA gene was used to profile the diversity and abundance of microbial communities at each interval and the results showed that the phyla of Bacteroidates, Firmicutes, Proteobacteria, and Euryarchaeota had a dominant presence in the PCP-dechlorinating cultures. Methanosarcina, Syntrophobotulus, Anaeromusa, Zoogloea, Treponema, W22 (family of Cloacamonaceae), and unclassified Cloacamonales were found to be the dominant genera during PCP dechlorination with acetate. The microbial community structure became relatively stable as cycles increased. Treponema, W22, and unclassified Cloacamonales were firstly observed to be associated with PCP dechlorination in the present study. Methanosarcina that have been isolated or identified in PCP dechlorination cultures previously was apparently enriched in the PCP dechlorination cultures. Additionally, the iron-cycling bacteria Syntrophobotulus, Anaeromusa, and Zoogloea were enriched in the PCP dechlorination cultures indicated they were likely to play an important role in PCP dechlorination. These findings increase our understanding for the microbial and geochemical interactions inherent in the transformation of organic contaminants from iron rich soil, and further extend our knowledge of the PCP-transforming microbial communities in anaerobic soil conditions.     

Metabolic activity of subterranean microbial communities in deep granitic groundwater supplemented with methane and H2

It was previously concluded that opposing gradients of sulphate and methane, observations of 16S ribosomal DNA sequences displaying great similarity to those of anaerobic methane-oxidizing Archaea and a peak in sulphide concentration in groundwater from a depth of 250–350 m in Olkiluoto, Finland, indicated proper conditions for methane oxidation with sulphate. In the present research, pressure-resistant, gas-tight circulating systems were constructed to enable the investigation of attached and unattached anaerobic microbial populations from a depth of 327 m in Olkiluoto under in situ pressure (2.4 MPa), diversity, dissolved gas and chemistry conditions. Three parallel flow cell cabinets were configured to allow observation of the influence on microbial metabolic activity of 11 mℳ methane, 11 mℳ methane plus 10 mℳ H₂ or 2.1 mℳ O₂ plus 7.9 mℳ N₂ (that is, air). The concentrations of these gases and of organic acids and carbon, sulphur chemistry, pH and E_h, ATP, numbers of cultivable micro-organisms, and total numbers of cells and bacteriophages were subsequently recorded under batch conditions for 105 days. The system containing H₂ and methane displayed microbial reduction of 0.7 mℳ sulphate to sulphide, whereas the system containing only methane resulted in 0.2 mℳ reduced sulphate. The system containing added air became inhibited and displayed no signs of microbial activity. Added H₂ and methane induced increasing numbers of lysogenic bacteriophages per cell. It appears likely that a microbial anaerobic methane-oxidizing process coupled to acetate formation and sulphate reduction may be ongoing in aquifers at a depth of 250–350 m in Olkiluoto.     

Dynamics of a pig slurry microbial community during anaerobic storage and management

The microbial community of a pig slurry on a farm was monitored for 6 months using both molecular and cultural approaches. Sampling was carried out at all the different stages of effluent handling, from the rearing build-up to slurry spreading. Total DNA of each sample was extracted and analyzed by PCR-single-strand conformation polymorphism (SSCP) analysis using primers targeting the 16S rRNA genes from the archaeal and bacterial domains and also the Eubacterium-Clostridium, Bacillus-Streptococcus-Lactobacillus, and Bacteroides-Prevotella groups. A comparison of the SSCP profiles showed that there were rapid changes in the dominant bacterial community during the first 2 weeks of anaerobic storage and that the community was relatively stable thereafter. Several bacterial populations, identified as populations closely related to uncultured Clostridium and Porphyromonas and to Lactobacillus and Streptococcus cultured species commonly isolated from pig feces, remained present and dominant from the rearing build-up to the time of spreading. Enumeration of fecal indicators (enterococci and Escherichia coli) performed in parallel using cultural methods revealed the same trends. On the other hand, the archaeal community adapted slowly during pig slurry storage, and its diversity increased. A shift between two hydrogenotrophic methanogenic Methanobrevibacter populations from the storage pit to the pond was observed. Microorganisms present in pig slurry at the time of spreading could not be detected in soil after spreading by either molecular or cultural techniques, probably because of the detection limit inherent in the two techniques.     

Analysis of the anaerobic microbial community capable of degrading p-toluene sulphonate

Three strains of Clostridium sp., 14 (VKM B-2201), 42 (VKM B-2202), and 21 (VKM B-2279), two methanogens, Methanobacterium formicicum MH (VKM B-2198) and Methanosarcina mazei MM (VKM B-2199), and one sulfate-reducing bacterium, Desulfovibrio sp. SR1 (VKM B-2200), were isolated in pure cultures from an anaerobic microbial community capable of degrading p-toluene sulfonate. Strain 14 was able to degrade p-toluene sulfonate in the presence of yeast extract and bactotryptone and, like strain 42, to utilize p-toluene sulfonate as the sole sulfur source with the production of toluene. p-Toluene sulfonate stimulated the growth of Ms. mazei MM on acetate. The sulfate-reducing strain Desulfovibrio sp. SR1 utilized p-toluene sulfonate as an electron acceptor. The putative scheme of p-toluene sulfonate degradation by the anaerobic microbial community is discussed.     

Continuous production of glutathione using immobilized microbial cells containing ATP generating system

Acetate kinase reaction in Escherichia coli cells and glycolytic pathway in Saccharomyces cerevisiae cells were utilized as ATP generation systems for glutathione synthetic processes. These two ATP generation systems were well coupled with glutathione synthetase reactions and glutathione was produced by coimmobilized E. coli cells with dextran-bound ATP or by immobilized S. cerevisiae cells. The glycolytic pathway in S. cerevisiae cells was further utilized for the biosynthetic processes of other useful compounds.     

Linking microbial community structure,interactions and function in anaerobic digesters using new molecular techniques

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Whole-metagenome amplification of a microbial community associated with scleractinian coral by multiple displacement amplification using phi29 polymerase

Limitations in obtaining sufficient specimens and difficulties in extracting high quality DNA from environmental samples have impeded understanding of the structure of microbial communities. In this study, multiple displacement amplification (MDA) using phi29 polymerase was applied to overcome these hindrances. Optimization of the reaction conditions for amplification of the bacterial genome and evaluation of the MDA product were performed using cyanobacterium Synechocystis sp. strain PCC6803. An 8-h MDA reaction yielded a sufficient quantity of DNA from an initial amount of 0.4 ng, which is equivalent to approximately 10(5) cells. Uniform amplification of genes randomly selected from the cyanobacterial genome was confirmed by real-time polymerase chain reaction. The metagenome from bacteria associated with scleractinian corals was used for whole-genome amplification using phi29 polymerase to analyse the microbial diversity. Unidentified bacteria with less than 93% identity to the closest 16S rDNA sequences deposited in DNA Data Bank of Japan were predominantly detected from the coral-associated bacterial community before and after the MDA procedures. Sequencing analysis indicated that alpha-Proteobacteria was the dominant group in Pocillopora damicornis. This study demonstrates that MDA techniques are efficient for genome wide investigation to understand the actual microbial diversity in limited bacterial samples.     

Fermentative hydrogen production and bacterial community structure in high-rate anaerobic bioreactors containing silicone-immobilized and self-flocculated sludge

A novel continuously stirred anaerobic bioreactor (CSABR) seeded with silicone-immobilized sludge was developed for high-rate fermentative H2 production using sucrose as the limiting substrate. The CSABR system was operated at a hydraulic retention time (HRT) of 0.5-6 h and an influent sucrose concentration of 10-40 g COD/L. With a high feeding sucrose concentration (i.e., 30-40 g COD/L) and a short HRT (0.5 h), the CSABR reactor produced H2 more efficiently with the highest volumetric rate (VH2) of 15 L/h/L (i.e., 14.7 mol/d/L) and an optimal yield of ca. 3.5 mol H2/mol sucrose. The maximum VH2 value obtained from this work is much higher than any other VH2 values ever documented. Formation of self-flocculated granular sludge occurred during operation at a short HRT. The granule formation is thought to play a pivotal role in the dramatic enhancement of H2 production rate, because it led to more efficient biomass retention. A high biomass concentration of up to 35.4 g VSS/L was achieved even though the reactor was operated at an extremely low HRT (i.e., 0.5 h). In addition to gaining high biomass concentrations, formation of granular sludge also triggered a transition in bacterial community structure, resulting in a nearly twofold increase in the specific H2 production rate. According to denatured-gradient-gel-electrophoresis analysis, operations at a progressively decreasing HRT resulted in a decrease in bacterial population diversity. The culture with the best H2 production performance (at HRT = 0.5 h and sucrose concentration = 30 g COD/L) was eventually dominated by a presumably excellent H2-producing bacterial species identified as Clostridium pasteurianum.     

Effect of applied voltage and temperature on methane production and microbial community in microbial electrochemical anaerobic digestion systems treating swine manure

Journal of Industrial Microbiology & Biotechnology - Microbial electrochemical technology (MET) that can harvest electricity/valuable materials and enhance the efficiency of conventional...     

利用微生物电解池处理牛奶废水过程中产电菌落与产氢性能之间的关系

【目的】 研究微生物电解池(Microbial electrolysis cell, MEC)利用复杂有机物作为底物的运行特性, 对其在废水处理中的应用有着重要的意义。【方法】 以模拟牛奶废水为基质, 通过构建MEC反应器来考察在不同外加电压条件下产电菌群的性能。【结果】 当外加电压升高到1.2 V时, 最大电流密度可达到261 A/m3, 产氢速率可达0.048 m3 H2/m3 d, 分别比外加电压为0.4 V的情形提高了467%和700%。外加电压为1.2 V时, 系统对COD和蛋白质去除率可分别达59%和74%, 其中COD去除较之0.4 V的情形提高了22.5%。PCR-DGGE的分子生物学分析结果表明, 阳极生物膜中以Geobacter sp.作为优势菌, 说明在利用大分子有机物作为基质时产电菌与非产电菌的协同作用更为明显。【结论】 MEC能够利用牛奶废水作为燃料, 在实现高效降解的同时以产氢的形式进行能量产出, 这为MEC的实际应用提供了研究思路。     

木质纤维素燃料乙醇蒸馏废水的高温厌氧处理及菌群结构分析

【目的】为开发高效的高浓度木质纤维素燃料乙醇蒸馏废水厌氧处理及资源化利用工艺,以活性炭为载体,在实验室规模上对高温厌氧流化床反应器处理木质纤维素燃料乙醇蒸馏废水进行研究。【方法】反应器经65 d梯度驯化后启动,对工艺参数进行一系列优化,并通过基于16S rRNA基因的分子生态学技术分析厌氧污泥中的优势菌群。【结果】实验获得了最优的反应条件和处理效果:厌氧流化床反应器(Anaerobic fluidized bed reactor,AFBR)在温度55±1°C、有机负荷率(OLR)13.8 g COD/(L·d)及水力停留时间(HRT)48 h操作时,COD去除率达到90%以上,同时甲烷产率达到290 mL/g COD;菌群鉴定分析结果显示高温厌氧活性污泥中Clostridia所占比例最大,产甲烷菌属以Methanoculleus和Methanosarcina为主,其它功能菌群主要为Alphaproteobacteria等。【结论】AFBR反应器可高效降解木质纤维素燃料乙醇蒸馏废水并产生生物能源甲烷,其反应体系内微生物种类丰富。     

Metagenomic analysis of the microbial community associated with the coral Porites astreoides

The coral holobiont is a dynamic assemblage of the coral animal, zooxanthellae, endolithic algae and fungi, Bacteria,Archaea and viruses. Zooxanthellae and some Bacteria form relatively stable and species-specific associations with corals. Other associations are less specific; coral-associated Archaea differ from those in the water column, but the same archaeal species may be found on different coral species. It has been hypothesized that the coral animal can adapt to differing ecological niches by 'switching' its microbial associates. In the case of corals and zooxanthellae, this has been termed adaptive bleaching and it has important implications for carbon cycling within the coral holobiont and ultimately the survival of coral reefs. However, the roles of other components of the coral holobiont are essentially unknown. To better understand these other coral associates, a fractionation procedure was used to separate the microbes, mitochondria and viruses from the coral animal cells and zooxanthellae. The resulting metagenomic DNA was sequenced using pyrosequencing. Fungi, Bacteria and phage were the most commonly identified organisms in the metagenome. Three of the four fungal phyla were represented, including a wide diversity of fungal genes involved in carbon and nitrogen metabolism, suggesting that the endolithic community is more important than previously appreciated. In particular, the data suggested that endolithic fungi could be converting nitrate and nitrite to ammonia, which would enable fixed nitrogen to cycle within the coral holobiont. The most prominent bacterial groups were Proteobacteria (68%), Firmicutes (10%), Cyanobacteria (7%) and Actinobacteria (6%). Functionally, the bacterial community was primarily heterotrophic and included a number of pathways for the degradation of aromatic compounds, the most abundant being the homogentisate pathway. The most abundant phage family was the ssDNA Microphage and most of the eukaryotic viruses were most closely related to those known to infect aquatic organisms. This study provides a metabolic and taxonomic snapshot of microbes associated with the reef-building coral Porites astreoides and presents a basis for understanding how coral-microbial interactions structure the holobiont and coral reefs.     

Phylogenetic analysis of a microbial community involved in anaerobic oxidation of ammonium nitrogen

The phylogenetic diversity of a microbial community involved in anaerobic oxidation of ammonium nitrogen in the DEAMOX process was studied. Analysis of clone libraries containing 16S rRNA gene inserts of Bacteria, (including Planctomycetes) and Archaea revealed the presence of nucleotide sequences of the microorganisms involved in the main reactions of the carbon, nitrogen, and sulfur cycles, including nitrifying, denitrifying, and ANAMMOX bacteria. In the bacterial clone library, 16S rRNA gene sequences of representatives of the phyla Proteobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Verrucomicrobia, Lentisphaerae, Spirochaetales, and Planctomycetes, as well as of some new groups, were detected. In the archaeal clone library, nucleotide sequences of methanogens belonging to the orders Methanomicrobiales, Methanobacteriales, and Methanosarcinales were found. It is possible that both ANAMMOX bacteria and bacteria of the genus Nitrosomonas are involved in anaerobic ammonium oxidation in the DEAMOX reactor. Many sequences were similar to those from the clone libraries obtained previously from the ANAMMOX community of marine sediments. It is also probable that the DEAMOX reactions occur in natural ecosystems (in marine and freshwater sediments and the oceanic water column), thereby providing for the coupling of the nitrogen and sulfur cycles.     

Quantitative analysis of a high-rate hydrogen-producing microbial community in anaerobic agitated granular sludge bed bioreactors using glucose as substrate

Fermentative H₂ production microbial structure in an agitated granular sludge bed bioreactor was analyzed using fluorescence in situ hybridization (FISH) and polymerase chain reaction-denatured gradient gel electrophoresis (PCR-DGGE). This hydrogen-producing system was operated at four different hydraulic retention times (HRTs) of 4, 2, 1, and 0.5 h and with an influent glucose concentration of 20 g chemical oxygen demand/l. According to the PCR-DGGE analysis, bacterial community structures were mainly composed of Clostridium sp. (possibly Clostridium pasteurianum), Klebsiella oxytoca, and Streptococcus sp. Significant increase of Clostridium/total cell ratio (68%) was observed when the reactor was operated under higher influent flow rate. The existence of Streptococcus sp. in the reactor became more important when operated under a short HRT as indicated by the ratio of Streptococcus probe-positive cells to Clostridium probe-positive cells changing from 21% (HRT 4 h) to 38% (HRT 0.5 h). FISH images suggested that Streptococcus cells probably acted as seeds for self-flocculated granule formation. Furthermore, combining the inspections with hydrogen production under different HRTs and their corresponding FISH analysis indicated that K. oxytoca did not directly contribute to H₂ production but possibly played a role in consuming O₂ to create an anaerobic environment for the hydrogen-producing Clostridium.     

Distributional dynamics of a specialized subterranean community oppose the classical understanding of the preferred subterranean habitats

Troglobionts are organisms that are specialized for living in a subterranean environment. These organisms reside prevalently in the deepest zones of caves and in shallow subterranean habitats, and complete their entire life cycles therein. Because troglobionts in most caves depend on organic matter resources from the surface, we hypothesized that they would also select the sections of caves nearest the surface, as long as environmental conditions were favorable. Over 1 year, we analyzed, in monthly intervals, the annual distributional dynamics of a subterranean community consisting of 17 troglobiont species, in relation to multiple environmental factors. Cumulative standardized annual species richness and diversity clearly indicated the existence of two ecotones within the cave: between soil and shallow subterranean habitats, inhabited by soil and shallow troglobionts; and between the transition and inner cave zones, where the spatial niches of shallow and deep troglobionts overlap. The mean standardized annual species richness and diversity showed inverse relationships, but both contributed to a better insight into the dynamics of subterranean fauna. Regression analyses revealed that temperatures in the range 7–10°C, high moisture content of substrate, large cross section of the cave, and high pH of substrate were the most important ecological drivers governing the spatiotemporal dynamics of troglobionts. Overall, this study shows general trends in the annual distributional dynamics of troglobionts in shallow caves and reveals that the distribution patterns of troglobionts within subterranean habitats may be more complex than commonly assumed.