@article {3104, title = {Potential enhancement of direct interspecies electron transfer for syntrophic metabolism of propionate and butyrate with biochar in up-flow anaerobic sludge blanket reactors.}, journal = {Bioresour Technol}, volume = {209}, year = {2016}, month = {2016 Jun}, pages = {148-56}, abstract = {

Promoting direct interspecies electron transfer (DIET) to enhance syntrophic metabolism may be a strategy for accelerating the conversion of organic wastes to methane, but microorganisms capable of metabolizing propionate and butyrate via DIET under methanogenic conditions have yet to be identified. In an attempt to establish methanogenic communities metabolizing propionate or butyrate with DIET, enrichments were initiated with up-flow anaerobic sludge blanket (UASB), similar to those that were previously reported to support communities that metabolized ethanol with DIET that relied on direct biological electrical connections. In the absence of any amendments, microbial communities enriched were dominated by microorganisms closely related to pure cultures that are known to metabolize propionate or butyrate to acetate with production of H2. When biochar was added to the reactors there was a substantial enrichment on the biochar surface of 16S rRNA gene sequences closely related to Geobacter and Methanosaeta species known to participate in DIET.

}, keywords = {Acetates, Bioreactors, Butyric Acid, Charcoal, Electron Transport, Geobacter, Methane, Microbial Consortia, Propionates, RNA, Ribosomal, 16S, Sewage, Waste Disposal, Fluid}, issn = {1873-2976}, doi = {10.1016/j.biortech.2016.03.005}, author = {Zhao, Zhiqiang and Zhang, Yaobin and Holmes, Dawn E and Dang, Yan and Woodard, Trevor L and Nevin, Kelly P and Lovley, Derek R} } @article {3109, title = {Enhancing syntrophic metabolism in up-flow anaerobic sludge blanket reactors with conductive carbon materials.}, journal = {Bioresour Technol}, volume = {191}, year = {2015}, month = {2015 Sep}, pages = {140-5}, abstract = {

Syntrophic metabolism of alcohols and fatty acids is a critical step in anaerobic digestion, which if enhanced can better stabilize the process and enable shorter retention times. Direct interspecies electron transfer (DIET) has recently been recognized as an alternative route to hydrogen interspecies transfer as a mechanism for interspecies syntrophic electron exchange. Therefore, the possibility of accelerating syntrophic metabolism of ethanol in up-flow anaerobic sludge blanket (UASB) reactors by incorporating conductive materials in reactor design was investigated. Graphite, biochar, and carbon cloth all immediately enhanced methane production and COD removal. As the hydraulic retention time was decreased the increased effectiveness of treatment in reactors with conductive materials increased versus the control reactor. When these conductive materials were removed from the reactors rates of syntrophic metabolism declined to rates comparable to the control reactor. These results suggest that incorporating conductive materials in the design of UASB reactors may enhance digester effectiveness.

}, keywords = {Anaerobiosis, Bioreactors, Carbon, Charcoal, Electron Transport, Graphite, Hydrogen, Methane, Sewage, Waste Disposal, Fluid}, issn = {1873-2976}, doi = {10.1016/j.biortech.2015.05.007}, author = {Zhao, Zhiqiang and Zhang, Yaobin and Woodard, T L and Nevin, K P and Lovley, D R} } @article {3113, title = {Correlation between microbial community and granule conductivity in anaerobic bioreactors for brewery wastewater treatment.}, journal = {Bioresour Technol}, volume = {174}, year = {2014}, month = {2014 Dec}, pages = {306-10}, abstract = {

Prior investigation of an upflow anaerobic sludge blanket (UASB) reactor treating brewery wastes suggested that direct interspecies electron transfer (DIET) significantly contributed to interspecies electron transfer to methanogens. To investigate DIET in granules further, the electrical conductivity and bacterial community composition of granules in fourteen samples from four different UASB reactors treating brewery wastes were investigated. All of the UASB granules were electrically conductive whereas control granules from ANAMMOX (ANaerobic AMMonium OXidation) reactors and microbial granules from an aerobic bioreactor designed for phosphate removal were not. There was a moderate correlation (r=0.67) between the abundance of Geobacter species in the UASB granules and granule conductivity, suggesting that Geobacter contributed to granule conductivity. These results, coupled with previous studies, which have demonstrated that Geobacter species can donate electrons to methanogens that are typically predominant in anaerobic digesters, suggest that DIET may be a widespread phenomenon in UASB reactors treating brewery wastes.

}, keywords = {Alcoholic Beverages, Anaerobiosis, Bacteria, Bioreactors, Electric Conductivity, Ethanol, Sequence Analysis, DNA, Sewage, Waste Disposal, Fluid, Wastewater, Water Purification}, issn = {1873-2976}, doi = {10.1016/j.biortech.2014.10.004}, author = {Shrestha, Pravin Malla and Malvankar, Nikhil S and Werner, Jeffrey J and Franks, Ashley E and Elena-Rotaru, Amelia and Shrestha, Minita and Liu, Fanghua and Nevin, Kelly P and Angenent, Largus T and Lovley, Derek R} } @article {755, title = {Expression and transfer of engineered catabolic pathways harbored by Pseudomonas spp. introduced into activated sludge microcosms.}, journal = {Appl Environ Microbiol}, volume = {58}, year = {1992}, month = {1992 Oct}, pages = {3380-6}, abstract = {Two genetically engineered microorganisms (GEMs), Pseudomonas sp. strain B13 FR1(pFRC20P) (FR120) and Pseudomonas putida KT2440(pWWO-EB62) (EB62), were introduced into activated sludge microcosms that had the level of aeration, nutrient makeup, and microbial community structure of activated sludge reactors. FR120 contains an experimentally assembled ortho cleavage route for simultaneous degradation of 3-chlorobenzoate (3CB) and 4-methyl benzoate (4MB); EB62 contains a derivative TOL plasmid-encoded degradative pathway for toluene experimentally evolved so that it additionally processes 4-ethyl benzoate (4EB). Experiments assessed survival of the GEMs, their ability to degrade target substrates, and lateral transfer of plasmid-encoded recombinant DNA. GEMs added at initial densities of 10(6) to 10(7) bacteria per ml of activated sludge declined to stable population densities of 10(4) to 10(5) bacteria per ml. FR120 degraded combinations of 3CB and 4MB (1 mM each) following 3 days of adaptation in the microcosms. Indigenous microorganisms required an 8-day adaptation period before degradation of 4MB was observed; 3CB was degraded only after the concentration of 4MB was much reduced. The indigenous microbial community was killed when both compounds were present at concentrations of 4.0 mM. However, in parallel microcosms containing FR120, the microbial community maintained a normal density of viable cells. Indigenous microbes readily degraded 4EB (2 mM), and EB62 did not significantly increase the observed rate of degradation. In filter matings, transfer of pFRC20P, which specifies mobilization but not transfer functions, from FR120 to P. putida UWC1 was not detectable (< 10(-7) transconjugants per donor cell).(ABSTRACT TRUNCATED AT 250 WORDS)}, keywords = {Benzoates, Biodegradation, Environmental, Gene Expression Regulation, Bacterial, Genetic Engineering, Industrial Waste, Pseudomonas, Transfection, Waste Disposal, Fluid}, issn = {0099-2240}, author = {N{\"u}sslein, K and Maris, D and Timmis, K and Dwyer, D F} }