• Document: Properties of Desulfovibrio carbinolicus sp. nov. and Other Sulfate- Reducing Bacteria Isolated from an Anaerobic-Purification Plant
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APPLIED AND ENVIRONMENTAL MICROBIOLOGY, Apr. 1987, p. 802-809 Vol. 53, No. 4 0099-2240/87/040802-08$02.00/0 Copyright C 1987, American Society for Microbiology Properties of Desulfovibrio carbinolicus sp. nov. and Other Sulfate- Reducing Bacteria Isolated from an Anaerobic-Purification Plant HENK J. NANNINGA AND JAN C. GOTTSCHAL* Department of Microbiology, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands Received 6 October 1986/Accepted 20 December 1986 Several sulfate-reducing microorganisms were isolated from an anaerobic-purification plant. Four strains were classified as Desulfovibrio desulfuricans, Desulfovibrio sapovorans, Desulfobulbus propionicus, and Desulfovibrio sp. The D. sapovorans strain contained poly-,-hydroxybutyrate granules and seemed to form extracellular vesicles. A fifth isolate, Desulfovibrio sp. strain EDK82, was a gram-negative, non-spore-forming, nonmotile, curved organism. It was able to oxidize several substrates, including methanol. Sulfate, sulfite, thiosulfate, and sulfur were utilized as electron acceptors. Pyruvate, fumarate, malate, and glycerol could be Downloaded from http://aem.asm.org/ on May 7, 2018 by guest fermented. Because strain EDK82 could not be ascribed to any of the existing species, a new species, Desulfovibrio carbinolicus, is proposed. The doubling times of the isolates were determined on several substrates. Molecular hydrogen, lactate, propionate, and ethanol yielded the shortest doubling times (3.0 to 6.3 h). Due to the presence of support material in an anaerobic ifiter system, these species were able to convert sulfate to sulfide very effectively at a hydraulic retention time as short as 0.5 h. Anaerobic treatment of wastewater rich in organic, sulfu- sulfide in the methane reactor and in the biogas can be rous compounds, inorganic sulfurous compounds, or both prevented, provided that all sulfate is converted into sulfide usually results in the formation of considerable quantities of before the sulfide stripper. In the first reactor the wastewater hydrogen sulfide, along with a whole range of other reduced contains several compounds that are suitable as electron sulfur-containing (organic) substances (4, 7, 10, 14, 21, 32, donors for the bacterial reduction of sulfate, such as ethanol, 33). In methanogenic digesters low sulfide concentrations acetate, propionate, and butyrate (27, 46; F. Widdel, Ph.D. (up to approx. 1 mM) have been shown to stimulate the thesis, University of Gottingen, Gottingen, Federal Republic anaerobic mineralization. This is quite understandable be- of Germany, 1980). Yet, at the hydraulic retention times cause its presence ensures strictly anaerobic conditions, reported above, only a partial conversion of sulfate takes several methanogens require sulfide for growth (2, 24, 36), place in the first reactor (27). In this study we attempted to and toxic metal ions are precipitated (15, 19, 23). However, answer the question of which factors are responsible for the high sulfide concentrations have been shown to reduce the incomplete removal of sulfate. To this end we investigate rate of methanogenesis (13, 14, 24, 30) and to cause unac- which species represent the dominating sulfate-reducing ceptable contamination of the biogas with H2S (13, 14). bacteria (SRB) in the purification plant and which com- Moreover, the sulfide present in the effluent of a methano- pounds can be used by them as electron donors. This genic digester results in an enhanced oxygen demand of the resulted in the isolation of several SRB and the description effluent, thus causing additional pollution of recipient wa- of a new, methanol-oxidizing, sulfate-reducing species. ters. Therefore, in methanogenic digesters the sulfide con- centration (H2S + HS- + S2-) should be kept well below 1 MATERIALS AND METHODS mM. Media and cultivation. A basal bicarbonate-buffered (pH Wastewater of the potato starch-producing factory of 7.0) freshwater medium with vitamins and trace elements Avebe (De Krim, The Netherlands) is very rich in readily was used as described previously (26). Acetate was supplied degradable organic matter (27, 28). After an initial only as indicated in the text. The amounts of yeast extract deproteination treatment, 7 to 8 g of organic carbon per liter and

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